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1
Morishita, Tomoaki, Masako Yoshikawa, Akihiro Tamura, Juan Guotana, and Biswajit Ghosh. "Petrology of Peridotites and Nd-Sr Isotopic Composition of Their Clinopyroxenes from the Middle Andaman Ophiolite, India." Minerals 8, no. 9 (September 17, 2018): 410. http://dx.doi.org/10.3390/min8090410.
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The Andaman Ophiolite, India, is located at the southeastern end of the Tethyan ophiolites. We examine petrology and mineralogy of two lherzolites and a completely serpentinized dunite associated with lherzolite from the middle Andaman Island. Major and trace element compositions of minerals in the lherzolites suggest their residual origin after low-degree of partial melting with less flux infiltration, and are similar to those of abyssal peridotites recovered from mid-ocean ridges. The dunite with spinels having low-Cr/(Cr + Al) ratio was formed by interaction between peridotite and mid-ocean ridge basalt-like melt. The 87Sr/86Sr and 143Nd/144Nd isotopic systematics of clinopyroxenes of the two lherzolites are consistent with MORB-type mantle source. Petrology and light rare earth element (LREE)-depleted patterns of clinopyroxene from the studied lhezolites are the same as those from some of the western Tethyan ophiolites. The age-corrected initial εNd values of the Tethyan lherzolite clinopyroxenes with LREE-depleted patterns are likely to be consistent with the depleted mantle evolution line.
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Hervig, R. L., J. V. Smith, and J. B. Dawson. "Lherzolite xenoliths in kimberlites and basalts: petrogenetic and crystallochemical significance of some minor and trace elements in olivine, pyroxenes, garnet and spinel." Transactions of the Royal Society of Edinburgh: Earth Sciences 77, no. 3 (1986): 181–201. http://dx.doi.org/10.1017/s026359330001083x.
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ABSTRACTElectron and ion microprobe analyses for P, Si, Ti, Al, Cr, V, Sc, Fe, Mn, Mg, Ni, Co, Ca, Sr, Na, K and Li in olivine, pyroxenes and garnet in forty-two cold and twelve hot garnet lherzolites from kimberlites, nine spinel lherzolites from kimberlites and eighteen from alkali basalts, and one cold garnet lherzolite from the Malaita alnöite, are compared with published data for minerals occurring in lherzolite, harzburgite and eclogite xenoliths, for silicate megacrysts in kimberlites, and for silicate inclusions in diamonds. Despite wide ranges in the chemistry of minerals from garnet and spinel lherzolites, there are distinct regions in composition space that would enable determination of the parent lithology of disaggregated minerals in kimberlites and alkali basalts. Titanium correlates with Fe3+ in garnets. Chromium, Al, V and Sc are distributed similarly between silicates in lherzolites. Sodium correlates with trivalent ions in olivine, and increases with temperature. The distribution of Na, but not of K and Li, between olivine and clinopyroxene correlates with temperature. The regular partitioning of Ti, Mn and Ni places constraints on crystal-liquid partition coefficients. Above the stability temperature of mica, ‘metasomatising fluids’ may scavenge Cr and other trivalent ions as they increase Ti in silicates.
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Evadelvia Ginal Sambari, Villa. "KARAKTERISTIK KIMIA DAN MINERALOGI PADA LAPUKAN BATUAN ULTRABASA SEKITAR DANAU TOWUTI KABUPATEN LUWU TIMUR PROVINSI SULAWESI SELATAN." SIBATIK JOURNAL: Jurnal Ilmiah Bidang Sosial, Ekonomi, Budaya, Teknologi, dan Pendidikan 1, no. 4 (March 22, 2022): 473–80. http://dx.doi.org/10.54443/sibatik.v1i4.56.
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Daerah penelitian termasuk dalam mandala geologi sulawesi timur batuan tertua adalah batuan ophiolit yang terdiri dari ultrabasa termasuk dunit, harzburgit, lherzolit, piroksenit, webstrite, wehrilit dan serpentinite. Tujuan penelitian adalah menganalisis secara geokimia tipe dan jenis mineral yang terkandung pada tanah dari batuan dasar. Menentukan batuan dasar yang terlapukkan. Menganalisis indeks pelapukan pada tanah yang berada pada lokasi penelitian berdasarkan komposisi kimia. Metode yang digunakan, yakni pengambilan sampel (soil) dan pengambilan sampel batuan ultrabasa (badrock). Analisis Petrografi untuk menentukan ciri fisik batuan dan komposisi mineral, Analisis XRD (X- Ray Diffraction) untuk menentukan mineral hasil pelapukan batuan dan analisis XRF (X- Ray Fluorescence) menghasilkan konsentrasi elemen kimia pada soil dimana metode ini dapat menentukan tingkat pelapukan dengan mengunakan rumus CIW (Chemical Indekx Weathering). Hasil penelitian menunjukan bahwa pada daerah penelitian indeks pelapukan kimia (CIW) telah menunjukkan adanya pelapukan yang semakin besar dengan nilai tingkat pelapukan yang tinggi. Hal ini dipengaruhi oleh kehadiran mineral yang mudah melapuk, seperti piroksin dan plagioklas. Batuan ultrabasa yang terserpentinkan lebih lama terlapukkan, dibandingkan batuan ultrabasa yang tidak terserpentinkan. Koefisien relatif senyawa SiO2 dan MgO sebagai fungsi Fe, adalah indikator proses pelapukan kimiawi dalam pembentukan tanah.
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Fernández-Roig, M., G. Galán, and E. Mariani. "Crystal preferred orientation of olivine in mantle xenoliths from Catalonia (NE Spain) Orientación cristalina preferente del olivino en xenolitos mantélicos de Cataluña (NE de España)." Trabajos de Geología 36, no. 36 (September 12, 2018): 119. http://dx.doi.org/10.17811/tdg.36.2016.119-138.
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Abstract: Mantle xenoliths in Neogene-Quaternary alkaline volcanic rocks from the Catalan Volcanic Zone indicate that ≪anhydrous≫ spinel lherzolites, harzburgites and much subordinate olivine websterites form the lithospheric mantle of NE Iberian Peninsula. Olivine crystal preferred orientation, determined by indexation of electron-backscattered diffraction patterns, provides three types of deformation fabric: a dominant [010]-fiber type in peridotites and websterites equilibrated at high temperature, and subordinate orthorhombic and [100]-fiber types, which appear mostly in porphyroclas tic and equigranular lherzolites equilibrated at lower temperature.Keywords: Lithospheric mantle, lherzolites, harzburgites, websterites, olivine, deformation fabric.Resumen: Los xenolitos mantelitos en lavas alcalinas neógeno-cuaternarias de la Zona Volcánica de Cataluña indican que lherzolitas y harzburgitas ≪ anhidras≫ y con espinela son las rocas predominantes en el manto litosférico del NE de la Península Ibérica, con presencia también subordinada de websteritas olivínicas. Las orientaciones cristalográficas preferentes del olivino, determinadas por indexación de los espectros de difracción de electrones retrodispersados, muestran tres tipos de fábrica de deformación: una dominante, tipo axial [010], en peridotitas y websteritas equilibradas a alta temperatura, y otras subordinadas, de tipo ortorrómbico y axial [100], que aparecen en lherzolitas porfidoclásticas y equigranulares equilibradas a menor temperatura.Palabras clave: Manto litosférico, lherzolitas, harzburgitas, websterita, olivino, fábricas de deformación
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Akinin, Vyacheslav V., Julia Apt, Michael F. Roden, Don Francis, and Elizabeth Moll-Stalcup. "Compositional and thermal state of the upper mantle beneath the Bering Sea basalt province: evidence from the Chukchi Peninsula of Russia." Canadian Journal of Earth Sciences 34, no. 6 (June 1, 1997): 789–800. http://dx.doi.org/10.1139/e17-065.
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Nephelinites and basanites of the Enmelen volcanic field, Chukchi Peninsula, Russia, contain upper mantle xenoliths of relatively calcium- and magnesium-rich spinel lherzolites, pyroxenites, and megacrysts. The phase assemblages of the lherzolites require equilibration near 1.5 GPa, and calculated equilibration temperatures for most inclusions are in the range 850–1030 °C. These temperatures are similar to those calculated for lherzolite inclusions from other Bering Sea localities (Nunivak Island and Seward Peninsula) and are higher than temperatures expected for likely conductive geotherms beneath these volcanic fields. The relatively high temperatures may be the result of magma intrusion into the mantle lithosphere and consequent perturbation of the geotherm shortly before entrainment of the xenoliths in basalt. Two Enmelen lherzolites equilibrated at higher temperatures (1230–1240 °C) and provide further evidence for heating due to intrusive magmas. Some spinel lherzolite inclusions have flat rare earth element patterns and major and trace element abundances close to that of the bulk silicate earth. Based on the occurrence of similar fertile peridotites at Nunivak Island and Seward Peninsula, near-primitive mantle compositions appear to be common in the upper mantle beneath the Bering Sea. These peridotites may represent recent additions to the mantle lithosphere from mantle plumes related to the volcanism. Other Enmelen inclusions are relatively light rare earth element-enriched group I lherzolites metasomatized by a silicate melt, group II pyroxenites precipitated from a variety of melts, and augite megacrysts with convex-upward rare earth element patterns consistent with precipitation from the host basalts at high pressures.
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Dupuy, C., J. Dostal, and P. A. Boivin. "Geochemistry of ultramafic xenoliths and their host alkali basalts from Tallante, southern Spain." Mineralogical Magazine 50, no. 356 (June 1986): 231–39. http://dx.doi.org/10.1180/minmag.1986.050.356.06.
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AbstractUltramafic xenoliths enclosed in Plio-Quaternary alkali basalts from Tallante near Cartagne (southern Spain) are composed mainly of spinel lherzolites which are probably upper mantle residues. In many xenoliths, the spinel lherzolite is cut by pyroxenite or gabbroic anorthosite veinlets generally 0.2–3 cm thick. The clinopyroxenite veinlets were formed by high-pressure crystal-liquid segregation from alkali basalt magmas formed earlier than the host basalts, whereas mantle metasomatism played a role in the genesis of gabbroic anorthosites. Close to the contact with the veinlets, the spinel lherzolites are enriched in Ca, Fe, and some incompatible elements including light REE due to the migration of a fluid from the veinlets into the surrounding lherzolites. The host alkali basalts were derived from a heterogeneous, incompatible element-enriched upper-mantle source probably similar in composition and nature to the composite xenoliths, but were formed in a garnet stability field.
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Anderson, Helen J. "Gravity modelling of the lherzolite body at Lers (French Pyrenees); some regional implications." Geological Magazine 122, no. 1 (January 1985): 51–56. http://dx.doi.org/10.1017/s0016756800034075.
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AbstractLherzolites outcrop throughout the North Pyrenean Zone of the Pyrenees and are everywhere associated with metamorphosed carbonates. It has been suggested that heat from the cooling of the lherzolites was responsible for the high temperature metamorphism of the carbonates. A gravity survey reported here shows that the volume of the lherzolite body at Lers is approximately 0.8 km3. The maximum volume of carbonates that such a body could metamorphose is 3.2 km3. This latter value is so much less than the volume of carbonates inferred from field mapping that the lherzolite body cannot have been the sole source of heat for metamorphism of the carbonates.It has been suggested from seismic data that there is a step in the Moho beneath the North Pyrenean Fault in the central Pyrenees. Gravity anomalies reported here show that either the step is less than 10 km high or that the density contrast is very low at the base of the crust in the Pyrenees.
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Carswell, D. A. "The garnet-orthopyroxene Al barometer: problematic application to natural garnet lherzolite assemblages." Mineralogical Magazine 55, no. 378 (March 1991): 19–31. http://dx.doi.org/10.1180/minmag.1991.055.378.03.
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AbstractThe garnet-orthopyroxene Al barometer specifically considers the Al content of orthopyroxene in equilibrium with garnet resulting from Mg-Tschermaks substitution. It is demonstrated that P-T calibrations of this barometer derived solely from experimental data for the MAS system, such as that favoured by Finnerty and Boyd (1984, 1987) based on the data of MacGregor (1974), cannot be expected to yield meaningful pressure estimates for natural garnet lherzolite assemblages. The presence of additional CaO, FeO and Cr2O3 components in natural garnet lherzolites can be expected to influence substantially the Al partitioning between orthopyroxene, garnet and/or spinel at any particular P and T. Thus a more comprehensive barometer formulation is required, such as the one provided by Nickel and Green (1985) that is based on experimental data for the CMAS and SMACCR systems with thermodynamic modelling and addition of an Fe correction term.It is further emphasised that for orthopyroxenes in natural garnet lherzolites the amount of Al introduced as Mg-Tschermaks substitution cannot be assessed simply as the total Al cation content since such orthopyroxenes frequently contain Al cations linked to Na substitution in M2 sites or to Cr, Ti and possibly Fe3+ in M1 sites. Revised algorithms for the calculation of specific orthopyroxene contents are presented. Application to analytical data sets for garnet lherzolite zenolith suites in the Thaba Putsoa and Mothae kimberlites generates revised upper mantle P-T arrays which refute the widely accepted advocacy by Finnerty and Boyd (1984, 1987) and Finnerty (1989) of an upper-mantle palaeogeotherm beneath northern Lesotho that is markedly inflected to a higher thermal gradient at the depths of derivation of the more chemically fertile, porphyroclastic textured, xenoliths.
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O'Reilly, Suzanne Y., D. Chen, W. L. Griffin, and C. G. Ryan. "Minor elements in olivine from spinel lherzolite xenoliths: implications for thermobarometry." Mineralogical Magazine 61, no. 405 (April 1997): 257–69. http://dx.doi.org/10.1180/minmag.1997.061.405.09.
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AbstractThe proton microprobe has been used to determine contents of Ca, Ti, Ni, Mn and Zn in the olivine of 54 spinel lherzolite xenoliths from Australian and Chinese basalts. These data are compared with proton-probe data for Ni, Mn and Zn in the olivine of 180 garnet peridotite xenoliths from African and Siberian kimberlites. Fe, Mn, Ni and Zn contents are well-correlated; because the spinel lherzolite olivines have higher mean Fe contents than garnet peridotite olivines (average Fo89.6vs. Fo90–92) they also have lower Ni and higher Mn contents. Zn and Fe are well-correlated in garnet peridotite olivine, but in spinel peridotites this relationship is perturbed by partitioning of Zn into spinel. None of these elements shows significant correlation with temperature. Consistent differences in trace-element contents of olivines in the two suites is interpreted as reflecting the greater degree of depletion of Archean garnet peridotites as compared to Phanerozoic spinel lherzolites. Ca and Ti contents of spinel-peridotite olivine are well correlated with one another, and with temperature as determined by several types of geothermometer. However, Ca contents are poorly correlated with pressure as determined by the Ca-in-olivine barometer of Köhler and Brey (1990). This reflects the strong T-dependence of this barometer: the uncertainty in pressure (calculated by this method) which is produced by the ±50°C uncertainty expected of any geothermometer is ca ± 8 kbar, corresponding to the entire width of the spinel-lherzolite field at 900–1200°C.
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Andronikov, Alexandre V., Irina E. Andronikova, and Tamara Sidorinova. "Trace-Element Geochemistry of Sulfides in Upper Mantle Lherzolite Xenoliths from East Antarctica." Minerals 11, no. 7 (July 16, 2021): 773. http://dx.doi.org/10.3390/min11070773.
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Sulfides in upper mantle lherzolite xenoliths from Cretaceous alkaline-ultramafic rocks in the Jetty Peninsula (East Antarctica) were studied for their major and trace-element compositions using SEM and LA-ICP-MS applied in situ. Modal abundance of sulfides is the lowest in Cpx-poor lherzolites ≤ Spl-Grt lherzolites << Cpx-rich lherzolites. Most sulfides are either interstitial (i-type) or inclusions in rock-forming minerals (e-type) with minor sulfide phases mostly present in metasomatic veinlets and carbonate-silicate interstitial patches (m-type). The main sulfide assemblage is pentlandite + chalcopyrite ± pyrrhotite; minor sulfides are polydymite, millerite, violarite, siegenite, and monosulfide solution (mss). Sulfide assemblages in the xenolith matrix are a product of the subsolidus re-equilibration of primary mss at temperatures below ≤300 °C. Platinum group elements (PGE) abundances suggest that most e-type sulfides are the residues of melting processes and that the i-type sulfides are crystallization products of sulfide-bearing fluids/liquids. The m-type sulfides might have resulted from low-temperature metasomatism by percolating sulfide-carbonate-silicate fluids/melts. The PGE in sulfide record processes are related to partial melting in mantle and intramantle melt migration. Most other trace elements initially partitioned into interstitial sulfide liquid and later metasomatically re-enriched residual sulfides overprinting their primary signatures. The extent of element partitioning into sulfide liquids depends on P, T, fO2, and host peridotite composition.
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Arai, Shoji, Akihiro Tamura, Makoto Miura, and Kazuma Seike. "Abyssal Peridotite as a Component of Forearc Mantle: Inference from a New Mantle Xenolith Suite of Bankawa in the Southwest Japan Arc." Minerals 8, no. 11 (November 21, 2018): 540. http://dx.doi.org/10.3390/min8110540.
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Lithology and petrologic nature of the forearc mantle have been left unclear due to the very limited sampling to date. Here, we present petrological data on a forearc peridotite suite obtained as xenoliths in an alkali basalt dike (7.5 Ma) from the Bankawa area in the Southwest Japan arc for our better understanding of the forearc mantle. The host alkali basalt is of asthenosphere origin, and passed through a slab window with slight chemical modification by the slab-derived component. The Bankawa peridotite suite is comprised of lherzolites, which contain various amounts of secondary phlogopite and were metasomatized to various degrees. The least metasomatized lherzolite exhibits Fo91 of olivine, Cr/(Cr + Al) = 0.3 of chromian spinel, and depletion of middle to light rare-earth elements in clinopyroxene, and is overall similar to an abyssal lherzolite. It had originally formed at the proto-Pacific Ocean and then was trapped at a eastern margin of Eurasian continent by initiation of subduction. The forearc mantle peridotite formed as a residue of proto-arc magma formation is depleted harzburgite as represented by the peridotites obtained from the forearc seafloor, but can be less depleted abyssal peridotite if being devoid of partial melting or reaction with magmas after entrapment.
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Giannakopoulou, P. P., B. Tsikouras, and K. Hatzipanagiotou. "THE INTERDEPENDENCE OF MECHANICAL PROPERTIES AND PETROGRAPHIC CHARACTERISTICS OF ULTRAMAFIC ROCKS FROM GERANIA OPHIOLITIC COMPLEX." Bulletin of the Geological Society of Greece 50, no. 4 (July 28, 2017): 1829. http://dx.doi.org/10.12681/bgsg.11922.
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Ultramafic rocks from the Gerania Mountain ophiolite were tested as aggregates. Petrographic study through polarizing microscope enabled us to determine the presence of dunite, harzburgite and lherzolite. A series of mechanical tests were carried out in order to determine the suitability of these rocks in a wide range of applications. Dunite and harzburgite samples show higher values of uniaxial compression strength than the lherzolites, as the presence of joints and the higher degree of alteration significantly affects negatively this mechanical property in the last rock-type. The same factors influence the point load index, too. Serpentinization and the presence of soft and laminate minerals also exert a negative influence on the resistance on abrasion and attrition, as well as the grinding of the rocks. The same factors influence negatively the point load index, too.
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Correia, Eugénio A., and Fernando A. T. P. Laiginhas. "Garnets from the Camafuca-Camazambo kimberlite (Angola)." Anais da Academia Brasileira de Ciências 78, no. 2 (June 2006): 309–15. http://dx.doi.org/10.1590/s0001-37652006000200010.
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This work presents a geochemical study of a set of garnets, selected by their colors, from the Camafuca-Camazambo kimberlite, located on northeast Angola. Mantle-derived garnets were classified according to the scheme proposed by Grütter et al. (2004) and belong to the G1, G4, G9 and G10 groups. Both sub-calcic (G10) and Ca-saturated (G9) garnets, typical, respectively, of harzburgites and lherzolites, were identified. The solubility limit of knorringite molecule in G10D garnets suggests they have crystallized at a minimum pressure of about 40 to 45 kbar (4-4.5 GPa). The occurrence of diamond stability field garnets (G10D) is a clear indicator of the potential of this kimberlite for diamond. The chemistry of the garnets suggests that the source for the kimberlite was a lherzolite that has suffered a partial melting that formed basaltic magma, leaving a harzburgite as a residue.
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Kopylova, M. G., E. Tso, F. Ma, J. Liu, and D. G. Pearson. "The Metasomatized Mantle beneath the North Atlantic Craton: Insights from Peridotite Xenoliths of the Chidliak Kimberlite Province (NE Canada)." Journal of Petrology 60, no. 10 (October 1, 2019): 1991–2024. http://dx.doi.org/10.1093/petrology/egz061.
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Abstract We studied the petrography, mineralogy, thermobarometry and whole-rock chemistry of 120 peridotite and pyroxenite xenoliths collected from the 156–138 Ma Chidliak kimberlite province (Southern Baffin Island). Xenoliths from pipes CH-1, -6, -7 and -44 are divided into two garnet-bearing series, dunites–harzburgites–lherzolites and wehrlites–olivine pyroxenites. Both series show widely varying textures, from coarse to sheared, and textures of late formation of garnet and clinopyroxene. Some samples from the lherzolite series may contain spinel, whereas wehrlites may contain ilmenite. In CH-6, rare coarse samples of the lherzolite and wehrlite series were derived from P = 2·8 to 5·6 GPa, whereas predominant sheared and coarse samples of the lherzolite series coexist at P = 5·6–7·5 GPa. Kimberlites CH-1, -7, -44 sample mainly the deeper mantle, at P = 5·0–7·5 GPa, represented by coarse and sheared lherzolite and wehrlite series. The bulk of the pressure–temperature arrays defines a thermal state compatible with 35–39 mW m–2 surface heat flow, but a significant thermal disequilibrium was evident in the large isobaric thermal scatter, especially at depth, and in the low thermal gradients uncharacteristic of conduction. The whole-rock Si and Mg contents of the Chidliak xenoliths and their mineral chemistry reflect initial high levels of melt depletion typical of cratonic mantle and subsequent refertilization in Ca and Al. Unlike the more orthopyroxene-rich mantle of many other cratons, the Chidliak mantle is rich (∼83 vol%) in forsteritic olivine. We assign this to silicate–carbonate metasomatism, which triggered wehrlitization of the mantle. The Chidliak mantle resembles the Greenlandic part of the North Atlantic Craton, suggesting the former contiguous nature of their lithosphere before subsequent rifting into separate continental fragments. Another, more recent type of mantle metasomatism, which affected the Chidliak mantle, is characterized by elevated Ti in pyroxenes and garnet typical of all rock types from CH-1, -7 and -44. These metasomatic samples are largely absent from the CH-6 xenolith suite. The Ti imprint is most intense in xenoliths derived from depths equivalent to 5·5–6·5 GPa where it is associated with higher strain, the presence of sheared samples of the lherzolite series and higher temperatures varying isobarically by up to 200 °C. The horizontal scale of the thermal-metasomatic imprint is more ambiguous and could be as regional as tens of kilometers or as local as <1 km. The time-scale of this metasomatism relates to a conductive length-scale and could be as short as <1 Myr, shortly predating kimberlite formation. A complex protracted metasomatic history of the North Atlantic Craton reconstructed from Chidliak xenoliths matches emplacement patterns of deep CO2-rich and Ti-rich magmatism around the Labrador Sea prior to the craton rifting. The metasomatism may have played a pivotal role in thinning the North Atlantic Craton lithosphere adjacent to the Labrador Sea from ∼240 km in the Jurassic to ∼65 km in the Paleogene.
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Stolper, Edward M., Oliver Shorttle, Paula M. Antoshechkina, and Paul D. Asimow. "The effects of solid-solid phase equilibria on the oxygen fugacity of the upper mantle." American Mineralogist 105, no. 10 (October 1, 2020): 1445–71. http://dx.doi.org/10.2138/am-2020-7162.
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Abstract Decades of study have documented several orders of magnitude variation in the oxygen fugacity (fO2) of terrestrial magmas and of mantle peridotites. This variability has commonly been attributed either to differences in the redox state of multivalent elements (e.g., Fe3+/Fe2+) in mantle sources or to processes acting on melts after segregation from their sources (e.g., crystallization or degassing). We show here that the phase equilibria of plagioclase, spinel, and garnet lherzolites of constant bulk composition (including whole-rock Fe3+/Fe2+) can also lead to systematic variations in fO2 in the shallowest ~100 km of the mantle. Two different thermodynamic models were used to calculate fO2 vs. pressure and temperature for a representative, slightly depleted peridotite of constant composition (including total oxygen). Under subsolidus conditions, increasing pressure in the plagioclase-lherzolite facies from 1 bar up to the disappearance of plagioclase at the lower pressure limit of the spinel-lherzolite facies leads to an fO2 decrease (normalized to a metastable plagioclase-free peridotite of the same composition at the same pressure and temperature) of ~1.25 orders of magnitude. The spinel-lherzolite facies defines a minimum in fO2 and increasing pressure in this facies has little influence on fO2 (normalized to a metastable spinel-free peridotite of the same composition at the same pressure and temperature) up to the appearance of garnet in the stable assemblage. Increasing pressure across the garnet-lherzolite facies leads to increases in fO2 (normalized to a metastable garnet-free peridotite of the same composition at the same pressure and temperature) of ~1 order of magnitude from the low values of the spinel-lherzolite facies. These changes in normalized fO2 reflect primarily the indirect effects of reactions involving aluminous phases in the peridotite that either produce or consume pyroxene with increasing pressure: Reactions that produce pyroxene with increasing pressure (e.g., forsterite + anorthite ⇄ Mg-Tschermak + diopside in plagioclase lherzolite) lead to dilution of Fe3+-bearing components in pyroxene and therefore to decreases in normalized fO2, whereas pyroxene-consuming reactions (e.g., in the garnet stability field) lead initially to enrichment of Fe3+-bearing components in pyroxene and to increases in normalized fO2 (although this is counteracted to some degree by progressive partitioning of Fe3+ from the pyroxene into the garnet with increasing pressure). Thus, the variations in normalized fO2 inferred from thermodynamic modeling of upper mantle peridotite of constant composition are primarily passive consequences of the same phase changes that produce the transitions from plagioclase → spinel → garnet lherzolite and the variations in Al content in pyroxenes within each of these facies. Because these variations are largely driven by phase changes among Al-rich phases, they are predicted to diminish with the decrease in bulk Al content that results from melt extraction from peridotite, and this is consistent with our calculations. Observed variations in FMQ-normalized fO2 of primitive mantle-derived basalts and peridotites within and across different tectonic environments probably mostly reflect variations in the chemical compositions (e.g., Fe3+/Fe2+ or bulk O2 content) of their sources (e.g., produced by subduction of oxidizing fluids, sediments, and altered oceanic crust or of reducing organic material; by equilibration with graphite- or diamond-saturated fluids; or by the effects of partial melting). However, we conclude that in nature the predicted effects of pressure- and temperature-dependent phase equilibria on the fO2 of peridotites of constant composition are likely to be superimposed on variations in fO2 that reflect differences in the whole-rock Fe3+/Fe2+ ratios of peridotites and therefore that the effects of phase equilibria should also be considered in efforts to understand observed variations in the oxygen fugacities of magmas and their mantle sources.
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Lorand, Jean-Pierre, Ambre Luguet, Olivier Alard, Antoine Bezos, and Thomas Meisel. "Abundance and distribution of platinum-group elements in orogenic lherzolites; a case study in a Fontete Rouge lherzolite (French Pyrénées)." Chemical Geology 248, no. 3-4 (February 2008): 174–94. http://dx.doi.org/10.1016/j.chemgeo.2007.06.030.
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Borghini, Giulio, and Patrizia Fumagalli. "Melting relations of anhydrous olivine-free pyroxenite Px1 at 2 GPa." European Journal of Mineralogy 32, no. 2 (March 23, 2020): 251–64. http://dx.doi.org/10.5194/ejm-32-251-2020.
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Abstract. The reaction between melt derived by mafic heterogeneities and peridotites in an upwelling mantle may form hybrid olivine-free pyroxenites. In order to evaluate the impact of these lithologies on the chemistry of primitive magmas and their ability to give rise to new mantle heterogeneities, we experimentally investigate the melting relations at 2 GPa of the model olivine-free pyroxenite Px1 (XMg=0.81, SiO2=52.9 wt %, Al2O3 = 11.3 wt %, CaO = 7.6 wt %). The subsolidus assemblage consists of clinopyroxene, orthopyroxene, and garnet. At 2 GPa, the solidus of Px1 is located between 1250 and 1280 ∘C, at a temperature about 70 ∘C lower than the solidus of fertile lherzolite. At increasing melt fraction, the sequence of mineral phase disappearance is garnet–clinopyroxene–orthopyroxene. Across the solidus, partial melting of Px1 is controlled by reaction garnet + clinopyroxene = liquid + orthopyroxene, and above 1300 ∘C, once garnet is completely consumed, by reaction clinopyroxene + orthopyroxene = liquid. Orthopyroxene is the liquidus phase, and at 1480 ∘C olivine-free pyroxenite Px1 is completely molten indicating a melting interval of about 200 ∘C. Isobaric melt productivity is similar to garnet clinopyroxenites, and it is more than 3 times that of a fertile lherzolite at 1400 ∘C. Px1 partial melts cover a wide range of XMg (0.57–0.84), with SiO2, Al2O3 and Na2O decreasing and Cr2O3 increasing with the degree of melting. CaO content in partial melts increases as long as clinopyroxene is involved in melting reactions and decreases after its exhaustion. At 2 GPa and for melting degrees higher than 10 %, Px1 produces MgO-rich basaltic andesites matching the composition of eclogitic melts in terms of silica and alkali contents but with significantly higher XMg values. These melts differ from those derived from lherzolites at 2 GPa by higher SiO2 and lower CaO contents. Their high silica activity makes them very reactive with mantle peridotite producing hybrid orthopyroxene-rich lithologies and residual websterites. Melt–rock reactions likely prevent direct extraction of melts produced by olivine-free pyroxenites.
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Hutchison, R., C. T. Williams, P. Henderson, and S. J. B. Reed. "New varieties of mantle xenolith from the Massif Central, France." Mineralogical Magazine 50, no. 358 (December 1986): 559–65. http://dx.doi.org/10.1180/minmag.1986.050.358.02.
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AbstractSpinel lherzolite xenoliths from two localities in the Massif Central are undepleted in Al2O3, CaO, and Na2O. One suite from Tarreyres, is K2O depleted and amphibole-bearing whereas the other, from Monistrol d'Allier some 18 km away, is amphibole-free and has a higher mean K2O content of 0.035 wt.%. We present bulk major and minor element abundances in a harzburgite and a lherzolite from each locality and microprobe analyses of their constituent phases. Amphibole-bearing lherzolite and its pyroxenes are light-rare earth element (LREE) depleted, whereas amphibole-free lherzolite and its pyroxenes are LREE enriched. Both harzburgites and their pyroxenes are LREE enriched and one rock contains LREE enriched glass. The harzburgites are like harzburgite xenoliths from elsewhere but each lherzolite represents a previously unrecognized type of mantle in terms of the mineralogy and REE content. The implication for basalt genesis are briefly discussed.
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Klemme, Stephan, and Hugh StC O'Neill. "The near-solidus transition from garnet lherzolite to spinel lherzolite." Contributions to Mineralogy and Petrology 138, no. 3 (March 2000): 237–48. http://dx.doi.org/10.1007/s004100050560.
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Shirdashtzadeh, Nargess, and Ghodrat Torabi. "Serpentinization and chloritization of metamorphosed lherzolites in Darreh-Deh (east of Nain Ophiolite, Central Iran): Calcium source for rodingitization and tremolitization." Neues Jahrbuch für Mineralogie - Abhandlungen Journal of Mineralogy and Geochemistry 196, no. 3 (July 1, 2020): 179–91. http://dx.doi.org/10.1127/njma/2019/0163.
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The petrography and mineral chemistry of the metamorphosed lherzolite in Darreh-Deh massif (east of Nain Ophiolite, Central Iran) is investigated in order to find the calcium source for rodingitization and tremolitization. In comparison with olivine and orthopyroxene, the clinopyroxene has lower modal content and is more alteration-resistant. The microprobe data and petrography of these lherzolites indicate that Ca2+ cations can be released during serpentinization of orthopyroxene (with ~18 vol% and CaO~2.7 wt%) and clinopyroxene (with ~6 vol% and CaO~ > 20 wt%). In contrast, per- vasive serpentinization of mantle olivine with ~70 vol% and CaO~0.02–0.07 wt% is another expected source for producing Ca2+ rather than metamorphic olivine with CaO~ < 0.02 wt%. The released Ca2+ cannot be completely accommodated in crystal lattice of produced serpentine (with CaO~0.02–0.06 wt%), talc and chlorite (with CaO~0.015 wt%), but it can participate in formation of Ca-bearing tremolite (CaO~13 wt%), as a result of serpentinization of clinopyroxenes or subsequent metamorphism of peridotites at amphibolite facies and in formation of coarse-grained clinopyroxene blades and tremolite during rodingitization. Therefore, the calcium content in clinopyroxene, orthopyroxene and olivine of a plagioclase–free peridotite is a potential source of Ca2+, depending on the degree of serpentinization or chloritization.
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Garuti, Giorgio, Evgenii V. Pushkarev, Irina A. Gottman, and Federica Zaccarini. "Chromite-PGM Mineralization in the Lherzolite Mantle Tectonite of the Kraka Ophiolite Complex (Southern Urals, Russia)." Minerals 11, no. 11 (November 19, 2021): 1287. http://dx.doi.org/10.3390/min11111287.
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The mantle tectonite of the Kraka ophiolite contains several chromite deposits. Two of them consisting of high-Cr podiform chromitite—the Bolshoi Bashart located within harzburgite of the upper mantle transition zone and Prospect 33 located in the deep lherzolitic mantle—have been investigated. Both deposits are enveloped in dunite, and were formed by reaction between the mantle protolith and high-Mg, anhydrous magma, enriched in Al2O3, TiO2, and Na2O compared with boninite. The PGE mineralization is very poor (<100 ppb) in both deposits. Laurite (RuS2) is the most common PGM inclusion in chromite, although it is accompanied by erlichmanite (OsS2) and (Ir,Ni) sulfides in Prospect 33. Precipitation of PGM occurred at sulfur fugacity and temperatures of logƒS2 = (−3.0), 1300–1100 °C in Bolshoi Bashart, and logƒS2 = (−3.0/+1.0), 1100–800 °C in Prospect 33, respectively. The paucity of chromite-PGM mineralization compared with giant chromite deposits in the mantle tectonite in supra-subduction zones (SSZ) of the Urals (Ray-Iz, Kempirsai) is ascribed to the peculiar petrologic nature (low depleted lherzolite) and geodynamic setting (rifted continental margin?) of the Kraka ophiolite, which did not enable drainage of the upper mantle with a large volume of mafic magma.
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Mikouchi, Takashi, and Taichi Kurihara. "Mineralogy and petrology of paired lherzolitic shergottites Yamato 000027, Yamato 000047, and Yamato 000097: Another fragment from a Martian “lherzolite” block." Polar Science 2, no. 3 (September 2008): 175–94. http://dx.doi.org/10.1016/j.polar.2008.06.003.
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van der Werf, Thomas, Vasileios Chatzaras, Leo Marcel Kriegsman, Andreas Kronenberg, Basil Tikoff, and Martyn R. Drury. "Constraints on the rheology of the lower crust in a strike-slip plate boundary: evidence from the San Quintín xenoliths, Baja California, Mexico." Solid Earth 8, no. 6 (December 21, 2017): 1211–39. http://dx.doi.org/10.5194/se-8-1211-2017.
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Abstract. The rheology of lower crust and its transient behavior in active strike-slip plate boundaries remain poorly understood. To address this issue, we analyzed a suite of granulite and lherzolite xenoliths from the upper Pleistocene–Holocene San Quintín volcanic field of northern Baja California, Mexico. The San Quintín volcanic field is located 20 km east of the Baja California shear zone, which accommodates the relative movement between the Pacific plate and Baja California microplate. The development of a strong foliation in both the mafic granulites and lherzolites, suggests that a lithospheric-scale shear zone exists beneath the San Quintín volcanic field. Combining microstructural observations, geothermometry, and phase equilibria modeling, we estimated that crystal-plastic deformation took place at temperatures of 750–890 °C and pressures of 400–560 MPa, corresponding to 15–22 km depth. A hot crustal geotherm of 40 ° C km−1 is required to explain the estimated deformation conditions. Infrared spectroscopy shows that plagioclase in the mafic granulites is relatively dry. Microstructures are interpreted to show that deformation in both the uppermost lower crust and upper mantle was accommodated by a combination of dislocation creep and grain-size-sensitive creep. Recrystallized grain size paleopiezometry yields low differential stresses of 12–33 and 17 MPa for plagioclase and olivine, respectively. The lower range of stresses (12–17 MPa) in the mafic granulite and lherzolite xenoliths is interpreted to be associated with transient deformation under decreasing stress conditions, following an event of stress increase. Using flow laws for dry plagioclase, we estimated a low viscosity of 1.1–1.3×1020 Pa ⋅ s for the high temperature conditions (890 °C) in the lower crust. Significantly lower viscosities in the range of 1016–1019 Pa ⋅ s, were estimated using flow laws for wet plagioclase. The shallow upper mantle has a low viscosity of 5.7×1019 Pa ⋅ s, which indicates the lack of an upper-mantle lid beneath northern Baja California. Our data show that during post-seismic transients, the upper mantle and the lower crust in the Pacific–Baja California plate boundary are characterized by similar and low differential stress. Transient viscosity of the lower crust is similar to the viscosity of the upper mantle.
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Munha, J., T. Palacios, N. D. Macrae, and J. Mata. "Petrology of ultramafic xenoliths from Madeira island." Geological Magazine 127, no. 6 (November 1990): 543–66. http://dx.doi.org/10.1017/s0016756800015442.
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AbstractUltramafic xenoliths from Madeira island are divided into dunite/websterite/wehrlite/clinopyroxenite (DWWC) and harzburgite/lherzolite suites; the harzburgite/lherzolite xenoliths show abundant deformational features and are more refractory (Fo = 90–91) than the DWWC suite (Fo = 77–88).DWWC xenoliths are spinel-bearing olivine ± orthophyroxene cumulates with intercumulus clinopyroxene and rare plagioclase, amphibole and phlogopite. Mineral chemistry and geothermobarometric data indicate that DWWC xenoliths crystallized at 1150–1300 °C from Madeiran alkalic basalts and accumulated in magma reservoir(s) located 36–45 km beneath the island.The harzburgite/lherzolite xenoliths are composed of olivine + orthopyroxene + spinel ± clinopyroxene ± (rare) phlogopite and display alkali feldspar or clinopyroxenite veins and crystal aggregates. The complex thermal evolution recorded by these xenoliths and the close similarity of clinopyroxene REE contents and calculated fO2 values in both harzburgites and DWWC cumulates are attributed to recent infiltration of the harzburgites by melts trapped or crystallized within the mantle; these features, and the refractory bulk chemistry of the harzburgite/lherzolite suite, support the interpretation that these xenoliths represent depleted oceanic lithosphere variously modified by magmatism associated with the genesis of Madeira island. The association of these upper mantle xenoliths with cumulates crystallized from Madeiran magmas (DWWC) suggests that the harzburgite/lherzolite suite originated in the uppermost mantle above magma storage zone(s), probably near the boundary between the mantle and the overlying oceanic crust.
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Gallagher, S., and R. Elsdon. "Spinel lherzolite and other xenoliths from a dolerite dyke in southwest Donegal." Geological Magazine 127, no. 2 (March 1990): 177–80. http://dx.doi.org/10.1017/s0016756800013868.
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AbstractA highly xenolithic dolerite dyke is described which contains a large number of spinel lherzolite xenoliths. The petrology of the dolerite and the xenolith suite is described and electron probe analyses presented for the mineral phases in one of the spinel lherzolite xenoliths. The dyke geochemistry is consistent with a Permo-Carboniferous age.
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Payot, Betchaida, Shoji Arai, Masako Yoshikawa, Akihiro Tamura, Mitsuru Okuno, and Danikko Rivera. "Mantle Evolution from Ocean to Arc: The Record in Spinel Peridotite Xenoliths in Mt. Pinatubo, Philippines." Minerals 8, no. 11 (November 8, 2018): 515. http://dx.doi.org/10.3390/min8110515.
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A suite of peridotite xenoliths were collected from lahar flow deposits located close to the summit of Mt. Pinatubo. Spinel harzburgite is the most dominant lithology among dunites, pyroxenites and websterites. A rare spinel lherzolite xenolith (P12-7) is also present in this suite. The spinel lherzolite has well-preserved protogranular texture with very minimal presence of secondary amphibole, low Cr# in the chromian spinel, and depleted and hump shaped patterns of chondrite-normalized rare earth element (REE) patterns for the clinopyroxenes. In contrast, the spinel harzburgites contain abundant secondary amphiboles and orthopyroxenes, higher Cr# in the spinel, and slightly elevated patterns for the chondrite-normalized REE patterns for the amphiboles. The spinel lherzolite also exhibits higher olivine Fo content for a given spinel Cr# compared to the spinel harzburgites. The spinel lherzolite is interpreted as a typical residue from partial melting of abyssal peridotites whereas the spinel harzburgites may have formed via partial melting with subsequent modification during the influx of fluids in the mantle wedge. Our results suggest that fragments of MOR-derived lithosphere exist in the mantle wedge beneath the Philippine island arc. This work provides evidence for the conversion of abyssal to arc peridotites in the mantle wedge.
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Duba, Al, and Steven Constable. "The electrical conductivity of lherzolite." Journal of Geophysical Research: Solid Earth 98, B7 (July 10, 1993): 11885–99. http://dx.doi.org/10.1029/93jb00995.
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De Vivo, B., A. Lima, and V. Scribano. "CO2 fluid inclusions in ultramafic xenoliths from the Iblean Plateau, Sicily, Italy." Mineralogical Magazine 54, no. 375 (June 1990): 183–94. http://dx.doi.org/10.1180/minmag.1990.054.375.05.
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AbstractThe Iblean Plateau (Southeastern Sicily, Italy) consists of a thick Meso-Cenozoic carbonate sequence with interbedded volcanic horizons (alkaline and tholeiitic basalts). The alkaline basalts contain ultramafic (peridotites and pyroxenites) and mafic xenoliths. The peridotites are spinel-bearing lherzolites and lherzolitic harzburgites, with porphyroblastic to protogranular texture. Pyroxenites consist of Cr-diopside-bearing and Al-augite-bearing websterites. The mineral chemistry of the nodules indicates temperatures between 700 and 1050°C.Fluid inclusions containing CO2 and (sometimes) various proportions of silicate glass have been studied in olivine, orthopyroxene and clinopyroxene. The secondary inclusions occur as trails of CO2-rich inclusions, often cross-cutting deformation lamellae. The few primary inclusions, generally empty, show clear evidence of decrepitation. Of the 390 inclusions examined, 97% homogenized to the liquid phase (Th → L = −43.9 to +30.9°C); 3% homogenized to the vapour phase (Th → V = + 20.5 to +30.3°C, yelding CO2 densities in the range 0.20–1.13 g/cm3. Assuming a trapping temperature of 1100°C, the corresponding trapping pressure for a pure CO2 system lies in the range 0.6–11.0 kbar, i.e. a depth of ∼2.2 to 42 km.The majority of CO2 trapping events in the xenoliths occurred from 2.2 to 11.0 kbar, with no major trapping events at pressures less than 2.3 kbar, indicating the absence of a shallow magma reservoir below the Iblean Plateau.
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Lloyd, F. E., A. D. Edgar, D. M. Forsyth, and R. L. Barnett. "The paragenesis of upper-mantle xenoliths from the Quaternary volcanics south-east of Gees, West Eifel, Germany." Mineralogical Magazine 55, no. 378 (March 1991): 95–112. http://dx.doi.org/10.1180/minmag.1991.055.378.08.
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AbstractGroup I xenoliths, orthopyroxene-rich and orthopyroxene-free, contain Cr-spinel and clinopyroxene ± phlogopite, and occur together with Group II clinopyroxenites ± Ti-spinel ± phlogopite in K-mafic pyroclastics southeast of Gees. The petrography and clinopyroxene chemistry of orthopyroxene-rich (opx-rich sub-group) Group I xenoliths is consistent with an ‘original’ harzburgitic mantle that has been transformed to lherzolite by the addition of endiopside. In harzburgites, orthopyroxenes are reacting to diopside + olivine + alkali-silicate melt, and, by inference, the orthopyroxene-free (opx-free subgroup) Group I, dunite-wehrlite series can be linked to the opx-rich sub-group via this reaction. Progressive enrichment of dunitic material in endiopside-diopside has resulted in the formation of wehrlite. Phlogopite is titaniferous and occurs as a trace mineral in opx-rich, Group I xenoliths, whereas substantial phlogopite vein-networks are confined to the opx-free sub-group (dunite-wehrlite series). Interstitial, alkali-felsic glass occurs are veins within, and as extensions of, the phlogopite networks. Clinopyroxenes in phlogopite-veined xenoliths are decreased in Mg/(Mg + FeTotal) (mg) and Cr and increased in Ti, Al and Ca, compared with clinopyroxenes in xenoliths which have trace phlogopite. It is proposed that harzburgitic and dunitic mantle has been infiltrated by a Ca- and alkalirich, hydrous silicate melt rather than an ephemeral carbonatite melt. Dunite has been transformed to phlogopite wehrlite by the invasion of a Ca-, Al-, Ti- and K-rich, hydrous silicate melt. Ca-activity was high initially in the melt and was reduced by clinopyroxene precipitation. This resulted in enhanced K-activity which led to phlogopite veining of clinopyroxene-rich mantle. Group II phlogopite clinopyroxenites contain Ti-spinel and salites that are distinct in their Ti, Al and Cr contents from endiopsides and diopsides in Group I xenoliths. It is unlikely that these Group II xenoliths represent the culmination of the infiltration processes that have transformed dunite to wehrlite, nor can they be related to the host melt. These xenoliths may have crystallised from Ca- and K-bearing, hydrous silicate melts in mantle channelways buffered by previously precipitated clinopyroxene and phlogopite. Gees lherzolites contain pyroxenes and spinel with distinctly lower Al contents than these same minerals in lherzolites described previously from other West Eifel localities, which may reflect a distinctive lithology and/or processes of modification for the Gees mantle.
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Borghini, Giulio, Patrizia Fumagalli, and Elisabetta Rampone. "Melt–rock interactions in a veined mantle: pyroxenite–peridotite reaction experiments at 2 GPa." European Journal of Mineralogy 34, no. 1 (February 16, 2022): 109–29. http://dx.doi.org/10.5194/ejm-34-109-2022.
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Abstract. Interaction between peridotite and pyroxenite-derived melts can significantly modify the mineralogy and chemistry of the upper mantle, enhancing its heterogeneity, by creating re-fertilized peridotites and secondary-type pyroxenites. We experimentally investigated the reaction between a fertile lherzolite and MgO-rich basaltic andesite produced by partial melting of an olivine-free pyroxenite at 2 GPa and 1300–1450 ∘C. The aim was to constrain the rate and style of melt–peridotite reaction mostly as a function of temperature, i.e. assuming variable physical status of the host peridotite. Experiments juxtaposed pyroxenite on a synthesized fertile lherzolite to evaluate the modal and mineral compositional changes in the fertile lherzolite resulting from the reaction with pyroxenite-derived melt. At 1300 and 1350 ∘C, the reaction produces a thin orthopyroxene-rich reaction zone confined between partially molten pyroxenite and modally unmodified subsolidus lherzolite. Chemical changes in minerals of the pyroxenite crystal mush suggest that element diffusion across the pyroxenite–peridotite interface, coupled with orthopyroxene precipitation, plays a role in the reactive crystallization of mantle pyroxenite veins. At 1380 and 1400 ∘C, infiltration of pyroxenite-derived melt significantly modifies the mineralogy and chemistry of the host peridotite by creating orthopyroxene-rich websterites and pyroxene-rich lherzolite. At 1450 ∘C, pyroxenitic melt fluxes into molten peridotite, enhancing peridotite melting and creating a melt-bearing dunite associated with a refractory harzburgite. At a given pressure, bulk compositions of hybrid rocks originating through melt–peridotite interaction are mostly controlled by the chemistry of the reacting melt. Interaction between pyroxenitic melt and peridotite causes XMg[XMg=Mg/(Mg+Fetot)] and XCr[XCr=Cr/(Cr+Al)] decrease and TiO2 increase in pyroxenes and spinel across the pyroxenite–peridotite boundary. Similar chemical gradients in minerals are observed in pyroxenite–peridotite associations from natural mantle sequences. The comparison with mineral chemistry variations derived by reaction experiments potentially represents a petrologic tool to discriminate between low- versus high-temperature melt–peridotite reactions.
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Grove, Timothy L., Eva S. Holbig, Jay A. Barr, Christy B. Till, and Michael J. Krawczynski. "Melts of garnet lherzolite: experiments, models and comparison to melts of pyroxenite and carbonated lherzolite." Contributions to Mineralogy and Petrology 166, no. 3 (August 22, 2013): 887–910. http://dx.doi.org/10.1007/s00410-013-0899-9.
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ZIMMERMAN, M. E. "Rheological Properties of Partially Molten Lherzolite." Journal of Petrology 45, no. 2 (February 1, 2004): 275–98. http://dx.doi.org/10.1093/petrology/egg089.
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WOODLAND, A. B., J. KORNPROBST, and B. J. WOOD. "Oxygen Thermobarometry of Orogenic Lherzolite Massifs." Journal of Petrology 33, no. 1 (February 1, 1992): 203–30. http://dx.doi.org/10.1093/petrology/33.1.203.
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Shervais, J. W., and S. B. Mukasa. "The Balmuccia Orogenic Lherzolite Massif, Italy." Journal of Petrology Special_Volume, no. 2 (January 1, 1991): 155–74. http://dx.doi.org/10.1093/petrology/special_volume.2.155.
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Riehle, J. R., J. R. Budahn, M. A. Lanphere, and D. A. Brew. "Rare earth element contents and multiple mantle sources of the transform-related Mount Edgecumbe basalts, southeastern Alaska." Canadian Journal of Earth Sciences 31, no. 5 (May 1, 1994): 852–64. http://dx.doi.org/10.1139/e94-078.
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Pleistocene basalt of the Mount Edgecumbe volcanic field (MEF) is subdivided into a plagioclase type and an olivine type. Olivine basalt crops out farther inboard from the nearby Fairweather transform than plagioclase basalt. Th/La ratios of plagioclase basalt are similar to those of mid-ocean-ridge basalt (MORB), whereas those of olivine basalt are of continental affinity. The olivine basalt has higher 87Sr/86Sr ratios than the plagioclase basalt.We model rare earth element (REE) contents of the olivine basalt, which resemble those of transitional MORB, by 10–15% partial melting of fertile spinel–plagioclase lherzolite followed by removal of 8–13% olivine. Normative mineralogy indicates melting in the spinel stability field. REE contents of an undersaturated basalt (sample 5L005) resemble those of Mauna Loa tholeiite and are modelled by 5–10% partial melting of fertile garnet lherzolite followed by 10% olivine removal. Plagioclase basalt resembles sample 5L005 in REE contents but is lower in other incompatible-element contents and 87Sr/86Sr ratios. Plagioclase basalt either originated in depleted garnet lherzolite or is a mixture of sample 5L005 and normal MORB; complex zoning of plagioclase and colinear Sc and Th contents are consistent with magma mixing.We conclude that olivine basalt originated in subcontinental spinel lherzolite and that plagioclase basalt may have originated in suboceanic lithosphere of the Pacific plate. Lithospheric melting seemingly requires vertical flow of mantle material, although there is no direct evidence at the MEF for crustal extension that might provide a mechanism for mantle advection. In any case, most MEF magmas are subalkaline because of moderately high degrees of partial melting at shallow depth.
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Rogkala, Aikaterini, Petros Petrounias, Basilios Tsikouras, Panagiota Giannakopoulou, and Konstantin Hatzipanagiotou. "Mineralogical Evidence for Partial Melting and Melt-Rock Interaction Processes in the Mantle Peridotites of Edessa Ophiolite (North Greece)." Minerals 9, no. 2 (February 17, 2019): 120. http://dx.doi.org/10.3390/min9020120.
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The Edessa ophiolite complex of northern Greece consists of remnants of oceanic lithosphere emplaced during the Upper Jurassic-Lower Cretaceous onto the Palaeozoic-Mesozoic continental margin of Eurasia. This study presents new data on mineral compositions of mantle peridotites from this ophiolite, especially serpentinised harzburgite and minor lherzolite. Lherzolite formed by low to moderate degrees of partial melting and subsequent melt-rock reaction in an oceanic spreading setting. On the other hand, refractory harzburgite formed by high degrees of partial melting in a supra-subduction zone (SSZ) setting. These SSZ mantle peridotites contain Cr-rich spinel residual after partial melting of more fertile (abyssal) lherzolite with Al-rich spinel. Chromite with Cr# > 60 in harzburgite resulted from chemical modification of residual Cr-spinel and, along with the presence of euhedral chromite, is indicative of late melt-peridotite interaction in the mantle wedge. Mineral compositions suggest that the Edessa oceanic mantle evolved from a typical mid-ocean ridge (MOR) oceanic basin to the mantle wedge of a SSZ. This scenario explains the higher degrees of partial melting recorded in harzburgite, as well as the overprint of primary mineralogical characteristics in the Edessa peridotites.
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Zhu, Ren Z., Pei Ni, Jun Y. Ding, Guo G. Wang, Ming S. Fan, and Su N. Li. "Metasomatic Processes in the Lithospheric Mantle Beneath the No. 30 Kimberlite (Wafangdian Region, North China Craton)." Canadian Mineralogist 57, no. 4 (July 15, 2019): 499–517. http://dx.doi.org/10.3749/canmin.1800066.
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AbstractThis paper presents the first major and trace element compositions of mantle-derived garnet xenocrysts from the diamondiferous No. 30 kimberlite pipe in the Wafangdian region, and these are used to constrain the nature and evolution of mantle metasomatism beneath the North China Craton (NCC). The major element data were acquired using an electron probe micro-analyzer and the trace element data were obtained using laser ablation inductively coupled plasma-mass spectrometry. Based on Ni-in-garnet thermometry, equilibrium temperatures of 1107–1365 °C were estimated for peridotitic garnets xenocrysts from the No. 30 kimberlite, with an average temperature of 1258 °C, and pressures calculated to be between 5.0 and 7.4 GPa. In a CaO versus Cr2O3 diagram, 52% of the garnets fall in the lherzolite field and 28% in the harzburgite field; a few of the garnets are eclogitic. Based on rare earth element patterns, the lherzolitic garnets are further divided into three groups. The compositional variations in garnet xenocrysts reflect two stages of metasomatism: early carbonatite melt/fluid metasomatism and late kimberlite metasomatism. The carbonatite melt/fluids are effective at introducing Sr and the light rare earth elements, but ineffective at transporting much Zr, Ti, Y, or heavy rare earth elements. The kimberlite metasomatic agent is highly effective at element transport, introducing, e.g., Ti, Zr, Y, and the rare earth elements. Combined with compositional data for garnet inclusions in diamonds and megacrysts from the Mengyin and Wafangdian kimberlites, we suggest that these signatures reflect a two-stage evolution of the sub-continental lithospheric mantle (SCLM) beneath the NCC: (1) early-stage carbonatite melt/fluid metasomatism resulting in metasomatic modification of the SCLM and likely associated with diamond crystallization; (2) late-stage kimberlite metasomatism related to the eruption of the 465 Ma kimberlite.
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Kruk, Aleksei, and Alexander Sokol. "Role of Volatiles in the Evolution of a Carbonatitic Melt in Peridotitic Mantle: Experimental Constraints at 6.3 GPa and 1200–1450 °C." Minerals 12, no. 4 (April 11, 2022): 466. http://dx.doi.org/10.3390/min12040466.
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Reconstruction of the mechanisms of carbonatitic melt evolution is extremely important for understanding metasomatic processes at the base of the continental lithospheric mantle (CLM). We have studied the interaction between garnet lherzolite and a carbonatitic melt rich in molecular CO2 and H2O in experiments at 6.3 GPa and 1200–1450 °C. The interaction with garnet lherzolite and H2O-bearing carbonatite melt leads to wehrlitization of lherzolite, without its carbonation. Introduction of molecular CO2 and H2O initiates carbonation of olivine and clinopyroxene with the formation of orthopyroxene and magnesite. Partial carbonation leads to the formation of carbonate–silicate melts that are multiphase saturated with garnet harzburgite. Upon complete carbonation of olivine already at 1200 °C, melts with 27–31 wt% SiO2 and MgO/CaO ≈ 1 are formed. At 1350–1450 °C, the interaction leads to an increase in the melt fraction and the MgO/CaO ratio to 2–4 and a decrease in the SiO2 concentration. Thus, at conditions of a thermally undisturbed CLM base, molecular CO2 and H2O dissolved in metasomatic agents, due to local carbonation of peridotite, can provide the evolution of agent composition from carbonatitic to hydrous silicic, i.e., similar to the trends reconstructed for diamond-forming high density fluids (HDFs) and genetically related proto-kimberlite melts.
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OBATA, M., and L. MORTEN. "Transformation of Spinel Lherzolite to Garnet Lherzolite in Ultramafic Lenses of the Austridic Crystalline Complex, Northern Italy." Journal of Petrology 28, no. 3 (June 1, 1987): 599–623. http://dx.doi.org/10.1093/petrology/28.3.599.
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Koppa, Matúš, Friedrich Koller, and Marián Putiš. "Petrology and geochemistry of a peridotite body in Central- Carpathian Paleogene sediments (Sedlice, eastern Slovakia)." Geologica Carpathica 65, no. 5 (October 1, 2014): 390–402. http://dx.doi.org/10.2478/geoca-2014-0022.
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Abstract We studied representative samples from a peridotite body situated NE of Sedlice village within the Central- Carpathian Paleogene sediments in the Central Western Carpathians. The relationship of the peridotite to the surrounding Paleogene sediments is not clear. The fractures of the brecciated peridotite margin are healed with secondary magnesite and calcite. On the basis of the presented bulk-rock and electron microprobe data, the wt. % amounts of mineral phases were calculated. Most of calculated “modal” compositions of this peridotite corresponds to harzburgites composed of olivine (∼70-80 wt. %), orthopyroxene (∼17-24 wt. %), clinopyroxene ( < 5 wt. %) and minor spinel ( < 1 wt. %). Harzburgites could originate from lherzolitic protoliths due to a higher degree of partial melting. Rare lherzolites contain porphyroclastic 1-2 mm across orthopyroxene (up to 25 wt. %), clinopyroxene (∼ 5-8 wt. %) and minor spinel ( < 0.75 wt. %). On the other hand, rare, olivine-rich dunites with scarce orthopyroxene porphyroclasts are associated with harzburgites. Metamorphic mineral assemblage of low-Al clinopyroxene (3), tremolite, chrysotile, andradite, Cr-spinel to chromite and magnetite, and an increase of fayalite component in part of olivine, indicate low-temperature metamorphic overprint. The Primitive Mantle normalized whole-rock REE patterns suggest a depleted mantle rock-suite. An increase in LREE and a positive Eu anomaly may be consequence of interactive metamorphic fluids during serpentinization. Similar rocks have been reported from the Meliatic Bôrka Nappe overlying the Central Western Carpathians orogenic wedge since the Late Cretaceous, and they could be a potential source of these peridotite blocks in the Paleogene sediments.
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Liu, Y. Y., A. L. Perchuk, and A. A. Ariskin. "High pressure metamorphism in the peridotitic cumulate of the Marun-Keu complex, Polar Urals." Петрология 27, no. 2 (April 2, 2019): 138–60. http://dx.doi.org/10.31857/s0869-5903272138-160.
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The Marun-Keu Complex of high-pressure rocks comprises granitoids, gneisses, schists, gabbroids and peridotites, which are unevenly and variably metamorphosed to the eclogite facies. A representative sample of garnet–amphibole lherzolite from the Mount Slyudyanaya area shows a cumulate texture and well preserved magmatic mafic minerals (olivine and pyroxenes) but practically no preserved plagioclase. The eclogite-facies metamorphism produced corona textures of newly formed minerals: amphibole, garnet, orthopyroxene and spinel. The metamorphic parameters of the garnet–amphibole lherzolite were estimated by geothermobarometry and by modeling phase equilibria at Р ~ 2.1 GPa and T ~ 640–740°C and are well consistent with our earlier estimate of the formation conditions of eclogites in the area. Computer simulation of the crystallization process of the gabbroic melt with the COMAGMAT program package, using literature data on the composition of the least altered plagioclase peridotites and gabbroids from the Marun-Keu Complex, shows that the mafic and ultramafic rocks are genetically interrelated: they crystallized in a single magmatic chamber. According to the modeling, the origin of the cumulate texture in the lherzolite was controlled by the peritectic reaction Ol + melt → Opx at a pressure of 0.7–0.8 GPa and a temperature of 1255–1268°C. Differences between thermodynamic parameters in the eclogites and garnet peridotites are discussed within the framework of a tectonic model for subduction and subsequent exhumation of the Baltica paleocontinent.
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Soulard, H. "Lherzolite Partial Melting: Closer to Primary Liquids." Mineralogical Magazine 58A, no. 2 (1994): 866–67. http://dx.doi.org/10.1180/minmag.1994.58a.2.186.
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Tatsumi, Yoshiyuki, and Takehiro Koyaguchi. "An absarokite from a phlogopite lherzolite source." Contributions to Mineralogy and Petrology 102, no. 1 (1989): 34–40. http://dx.doi.org/10.1007/bf01160189.
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HAMELIN, B., and C. ALLEGRE. "Lead isotope study of orogenic lherzolite massifs." Earth and Planetary Science Letters 91, no. 1-2 (December 1988): 117–31. http://dx.doi.org/10.1016/0012-821x(88)90155-0.
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Zindler, Alan, and Emil Jagoutz. "Lead isotope systematics in spinel lherzolite nodules." Chemical Geology 70, no. 1-2 (August 1988): 58. http://dx.doi.org/10.1016/0009-2541(88)90354-3.
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Grammatikopoulos, A. L., Sandra M. Barr, P. H. Reynolds, and R. Doig. "Petrology and age of the Mechanic Settlement Pluton, Avalon terrane, southern New Brunswick." Canadian Journal of Earth Sciences 32, no. 12 (December 1, 1995): 2147–58. http://dx.doi.org/10.1139/e95-167.
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The Mechanic Settlement Pluton, located at the northern margin of the Caledonian Highlands in southern New Brunswick, is composed of rocks ranging from ultramafic (lherzolite, plagioclase-bearing lherzolite) through mafic (mainly olivine gabbronorite and gabbro) to intermediate (quartz diorite and monzodiorite). Spatial distribution of these lithologies, textural features, and geochemistry are consistent with evolution of a tholeiitic mafic parent magma by crystal fractionation processes, with some evidence for magma mingling between evolved gabbroic and quartz dioritic magmas. The dioritic rocks form most of the southwestern (upper?) part of the pluton, whereas the varied gabbroic rocks with ultramafic layers form the northeastern part. U–Pb (zircon) dating of a quartz diorite sample from the southwestern part of the pluton indicates crystallization at 557 ± 3 Ma. Amphibole and phlogopite in two lherzolite samples from the northeastern part of the pluton gave 40Ar/39Ar dates of 550 ± 5 and 539 ± 5 Ma, respectively, indicating that the pluton cooled rapidly through the closure temperature for amphibole, with subsequent slower cooling to the time of phlogopite closure. The pluton is interpreted to be the intrusive equivalent of basaltic units in the host Coldbrook Group, analogous to granitic plutons elsewhere in the Caledonian Highlands which appear to be the intrusive equivalents of felsic volcanic rocks in the group. These plutonic and volcanic rocks represent a major, short-lived (ca. 560–550 Ma), dominantly bimodal igneous event, apparently related to late Precambrian extension within the Avalon terrane of southern New Brunswick.
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Rogkala, A., P. Petrounias, B. Tsikouras, and K. Hatzipanagiotou. "PETROGENETIC SIGNIFICANCE OF SPINELS FROM SERPENTINISED PERIDOTITES FROM THE VERIANAOUSA OPHIOLITE." Bulletin of the Geological Society of Greece 50, no. 4 (July 28, 2017): 1999. http://dx.doi.org/10.12681/bgsg.11946.
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The Veria-Naousa ophiolitic complex represents a dismembered ophiolite unit, which is superimposed on a basement consisting of rocks belonging to the Pelagonian and Axios (Almopias subzone) isopic zones in northern Greece. Mantle peridotites are composed of variably serpentinised lherzolite and harzburgite intruded by a sparse network of pyroxenitic dykes. The serpentinised lherzolite and harzburgite contain Alspinels (Cr#=38.83-42.52 and Mg#=58.94-64.77), Cr-spinels (Cr#=43.37-64.92 and Mg#=49.20-58.66) and magnesiochromites (Cr#=53.93 57.13 and Mg#=55.73- 61.71). All of them display commonly richer-in-Cr cores rimmed by secondary ferrian chromite and magnetite. Whole-rock geochemicall compositions and primary spinel chemical composition of these peridotites are analogous to peridotites that formed in a suprasubduction zone. Ιt is supported that the Mantle peridotites of the VeriaNaousa ophiolitic complex formed in a back-arc basin
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Shchukina, Elena V., Alexey M. Agashev, and Vladimir S. Shchukin. "Diamond-Bearing Root Beneath the Northern East European Platform (Arkhangelsk Region, Russia): Evidence from Cr-Pyrope Trace-Element Geochemistry." Minerals 9, no. 5 (April 30, 2019): 261. http://dx.doi.org/10.3390/min9050261.
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In this study, we reconstruct the composition and metasomatic evolution of the lithospheric mantle beneath the poorly-studied southern Arkhangelsk region, based on the geochemistry of 145 Cr-pyrope grains recovered from samples of modern rivers and stream sediments, to evaluate the diamond exploration potential of these territories. Based on the concentrations of Cr2O3, CaO, TiO2, and rare earth elements (REEs), the garnets are divided into four groups: (1) low-chromium lherzolitic pyropes with fractionated heavy REE patterns; (2) low- to medium-chromium pyropes of lherzolitic and megacryst associations with flat heavy REE patterns; (3) high-chromium lherzolitic pyropes with “humped” REE patterns; and (4) high-chromium and low-chromium lherzolitic and harzburgitic pyropes with sinusoidal REE patterns. The pyrope geochemistry suggests a multi-stage model for the evolution of the lithospheric mantle, including partial melting to different degrees and further metasomatic overprints by silicate and carbonatite melts. The results confirm that the lithospheric mantle beneath the study area is suitable for the formation and preservation of diamonds. The significant percentage of diamond-associated pyropes (15%) emphasizes the likelihood of high diamond contents in kimberlites to be discovered within the study area.
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Perchuk, A. L., A. A. Serdyuk, and N. G. Zinovievа. "Subduction sediment-lherzolite interaction at 2.9 GPa: effects of metasomatism and partial melting." Петрология 27, no. 5 (August 18, 2019): 503–24. http://dx.doi.org/10.31857/s0869-5903275503-524.
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We present the results of analogue experiments carried out in a piston–cylinder apparatus at 750–900°C and 2.9 GPa aimed to simulate metasomatic transformation of the fertile mantle caused by fluids and melts released from the subducting sediment. A synthetic H2O- and CO2-bearing mixture that corresponds to the average subducting sediment (GLOSS, Plank, Langmuir, 1998) and mineral fractions of natural lherzolite (analogue of a mantle wedge) were used as starting materials. Experiments demonstrate that the mineral growth in capsules is controlled by ascending fluid and hydrous melt (from 850°C) flows. Migration of the liquids and dissolved components develops three horizontal zones in the sedimentary layer with different mineral parageneses that slightly changed from run to run. In the general case, however, the contents of omphacite and garnet increase towards the upper boundary of the layer. Magnesite and omphacite (± garnet ± melt ± kyanite ± phengite) are widespread in the central zone of the sedimentary layer, whereas SiO2 polymorph (± kyanite ± phengite ± biotite ± omphacite ± melt) occurs in the lower zone. Clinopyroxene disappears at the base of lherzolite layer and the initial olivine is partially replaced by orthopyroxene (± magnesite) in all experiments. In addition, talc is formed in this zone at 750°C, whereas melt appears at 850°C. In the remaining volume of the lherzolite layer, metasomatic transformations affect only grain boundaries where orthopyroxene (± melt ± carbonate) is developed. The described transformations are mainly related to a pervasive flow of liquids. Mineral growth in the narrow wall sides of the capsules is probably caused by a focused flow: omphacite grows up in the sedimentary layer, and talc or omphacite with the melt grow up in the lherzolite layer. Experiments show that metasomatism of peridotite related to a subducting sediment, unlike the metasomatism related to metabasites, does not lead to the formation of garnet-bearing paragenesis. In addition, uprising liquid flows (fluid, melt) do not remove significant amounts of carbon from the metasedimentary layer to the peridotite layer. It is assumed that either more powerful fluxes of aqueous fluid or migration of carbonate-bearing rocks in subduction melanges are necessary for more efficient transfer of crustal carbon from metasediments to a mantle in subduction zones.
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Furnes, Harald, Harald Brekke, Jan Nordås, and Jan Hertogen. "Lower Palaeozoic convergent plate margin volcanism on Bømlo, southwest Norwegian Caledonides: geochemistry and petrogenesis." Geological Magazine 123, no. 2 (March 1986): 123–42. http://dx.doi.org/10.1017/s0016756800029782.
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AbstractMajor and trace element analyses of a Lower Palaeozoic metavolcanic sequence of convergent plate type from Bømlo, southwest Norwegian Caledonides, are presented and discussed. This sequence ranges in age from the Upper Cambrian through the Lower Silurian. Petrogenetic models for the lavas in terms of partial melting and crystal fractionation are discussed. Two models are presented for the metabasalts in order to explain their different trace element abundances and ratios:(1) REE modelling, assuming a mantle source with REE abundances twice chondritic, suggests progressively more varied sources with time. Thus the metabasalts from the oldest (Upper Cambrian–Lower Ordovician) Geitung Unit of primitive island arc type, and those of the mid-Ordovician Siggjo Complex of ‘Basin and Range’ type can be modelled in terms of high (around 25%) and moderate (around 5%) degrees of partial melting of spinel lherzolite, respectively. The metabasalts of the post-Ashgillian Vikafjord Group of typical continental flood basalts are compatible with moderate (c. 5–10%) degrees of partial melting of spinel- and garnet-lherzolite sources. The supposed Lower Silurian Langevåg Group of calc-alkaline ‘Andean’ type metabasalts, grading into alkaline to tholeiitic metabasalts of early marginal basin (youngest) character, require low (<5%) to moderate degrees of partial melting of amphibole-, garnet- and spinel-lherzolite sources, respectively.(2) Source heterogeneity, produced by subduction zone-derived enrichment of LIL elements, and contemporaneous stabilization of minor phases which accommodate HFS elements. This process, combined with possible continental contamination, may possibly yield the trace element concentrations and ratios of the different metabasalts by partial melting of modally similar mantle sources.