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Journal articles on the topic 'Petrology Dunite'

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Published: 4 June 2021

Last updated: 4 February 2022

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1

Bazylev, B. A., G. V. Ledneva, Ya V. Bychkova, N. N. Kononkova, T. G. Kuz’mina, and T. V. Romashova. "Estimation of the content and composition of trapped melt in dunite." Геохимия 64, no. 5 (May 23, 2019): 471–85. http://dx.doi.org/10.31857/s0016-7525645471-485.

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A method was developed for the quantitative estimation of the content of trapped melt in various dunite types and the composition of this melt on the basis of the major- and trace-element characteristics of the dunites and compositions of their chrome spinels. Our approach is advantageous over the method based on clinopyroxene geochemistry and clinopyroxene–melt partition coefficients for the contents of the light REE and more incompatible elements in melt, comparable with it for the middle REE, and possibly less accurate for the heavy REE and Sr. The estimated mean contents of trapped melt in dunites from ophiolite and concentrically zoned complexes are 1.0–1.5 wt %, which is probably typical of various dunite types, including cumulate dunites from layered complexes. These values are an order of magnitude higher than previous estimates. The correspondence between the compositions of calculated trapped melts in dunites and real natural melts indicates that the estimated contents of trapped melt in dunites are realistic, and the mineral–melt partition coefficients that were used in our calculations are valid for the complexes considered in this paper. In general, the proposed method is suitable for serpentinized dunites, including dunitic serpentinites.

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2

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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3

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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4

GAFFNEY, AMY M. "Environments of Crystallization and Compositional Diversity of Mauna Loa Xenoliths." Journal of Petrology 43, no. 6 (June 1, 2002): 963–81. http://dx.doi.org/10.1093/petrology/43.6.963.

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Abstract Two picrite flows from the SW rift zone of Mauna Loa contain xenoliths of dunite, harzburgite, lherzolite, plagioclase-bearing lherzolite and harzburgite, troctolite, gabbro, olivine gabbro, and gabbronorite. Textures and olivine compositions preclude a mantle source for the xenoliths, and rare earth element concentrations of xenoliths and clinopyroxene indicate that the xenolith source is not old oceanic crust, but rather a Hawaiian, tholeiitic-stage magma. Pyroxene compositions, phase assemblages and textural relationships in xenoliths indicate at least two different crystallization sequences. Calculations using the pMELTS algorithm show that the two sequences result from crystallization of primitive Mauna Loa magmas at 6 kbar and 2 kbar. Independent calculations of olivine Ni–Fo compositional variability in the plagioclase-bearing xenoliths over these crystallization sequences are consistent with observed olivine compositional variability. Two parents of similar bulk composition, but which vary in Ni content, are necessary to explain the olivine compositional variability in the dunite and plagioclase-free peridotitic xenoliths. Xenoliths probably crystallized in a small magma storage area beneath the rift zone, rather than the large sub-caldera magma reservoir. Primitive, picritic magmas are introduced to isolated rift zone storage areas during periods of high magma flux. Subsequent eruptions reoccupy these areas, and entrain and transport xenoliths to the surface.

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5

Rehfeldt, T., D. E. Jacob, R. W. Carlson, and S. F. Foley. "Fe-rich Dunite Xenoliths from South African Kimberlites: Cumulates from Karoo Flood Basalts." Journal of Petrology 48, no. 7 (April 3, 2007): 1387–409. http://dx.doi.org/10.1093/petrology/egm023.

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6

SEN, G., and D. C. PRESNALL. "Petrogenesis of Dunite Xenoliths from Koolau Volcano, Oahu, Hawaii: Implications for Hawaiian Volcanism." Journal of Petrology 27, no. 1 (February 1, 1986): 197–217. http://dx.doi.org/10.1093/petrology/27.1.197.

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7

Aizawa, Y., A. Barnhoorn, U. H. Faul, J. D. Fitz Gerald, I. Jackson, and I. Kovacs. "Seismic Properties of Anita Bay Dunite: an Exploratory Study of the Influence of Water." Journal of Petrology 49, no. 4 (October 11, 2007): 841–55. http://dx.doi.org/10.1093/petrology/egn007.

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8

Morishita, Tomoaki, Jinichiro Maeda, Sumio Miyashita, Hidenori Kumagai, Takeshi Matsumoto, and Henry J. B. Dick. "Petrology of local concentration of chromian spinel in dunite from the slow-spreading Southwest Indian Ridge." European Journal of Mineralogy 19, no. 6 (December 17, 2007): 871–82. http://dx.doi.org/10.1127/0935-1221/2007/0019-1773.

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9

KUBO, K. "Dunite Formation Processes in Highly Depleted Peridotite: Case Study of the Iwanaidake Peridotite, Hokkaido, Japan." Journal of Petrology 43, no. 3 (March 1, 2002): 423–48. http://dx.doi.org/10.1093/petrology/43.3.423.

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10

BATANOVA, V. G., A. N. PERTSEV, V. S. KAMENETSKY, A. A. ARISKIN, A. G. MOCHALOV, and A. V. SOBOLEV. "Crustal Evolution of Island-Arc Ultramafic Magma: Galmoenan Pyroxenite–Dunite Plutonic Complex, Koryak Highland (Far East Russia)." Journal of Petrology 46, no. 7 (February 25, 2005): 1345–66. http://dx.doi.org/10.1093/petrology/egi018.

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11

Facer, J., H. Downes, and A. Beard. "In situ Serpentinization and Hydrous Fluid Metasomatism in Spinel Dunite Xenoliths from the Bearpaw Mountains, Montana, USA." Journal of Petrology 50, no. 8 (July 6, 2009): 1443–75. http://dx.doi.org/10.1093/petrology/egp037.

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12

Appel, C. C., P. W. U. Appel, and H. R. Rollinson. "Complex chromite textures reveal the history of an early Archaean layered ultramafic body in West Greenland." Mineralogical Magazine 66, no. 6 (December 2002): 1029–41. http://dx.doi.org/10.1180/0026461026660075.

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Abstract Massive chromitite, banded chromitite and disseminated chromite grains are found in a ˜3800 Ma layered ultrabasic body in West Greenland. The major part of the ultrabasite is dominated by dunite. In the upper exposed part, harzburgite and sheets of gabbro-anorthosite occur. Chromite grains in dunites, and in massive and banded chromitites are homogeneous, with increasing Fe contents upwards in the intrusion. In harzburgites chromites show unusual and very complex textural relationships, with two generations ofchromites one replacing the other, and both exhibiting exsolution textures. In harzburgites, an Fe-rich chromite crystallized first. This first chromite exsolved two spinel phases in a very fine-scale pattern and ilmenite lamellae in a trellis pattern. The Fe-rich chromite was later partly replaced by Al-rich chromite, which crystallized contemporaneously with formation of a late gabbro-anorthositic melt. Subsequently, the Al-rich chromite exsolved a very fine-scale magnetite-rich phase. The exsolutions in the first generation chromite were formed under magmatic conditions. Exsolution of ilmenite lamellae in Fe-rich spinel was caused by oxidation under magmatic conditions.

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13

Mues-Schumacher, U., J. Keller, V. A. Kononova, and P. J. Suddaby. "Mineral chemistry and geochronology of the potassic alkaline ultramafic Inagli complex, Aldan Shield, eastern Siberia." Mineralogical Magazine 60, no. 402 (October 1996): 711–30. http://dx.doi.org/10.1180/minmag.1996.060.402.02.

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AbstractThe Inagli complex, one of several Mesozoic intrusive complexes of the Aldan Shield (Siberian Platform), exhibits a concentric structure comprising several alkaline ultramafic rock-types. A central dunite body is surrounded by olivine- and phlogopite-clinopyroxenites forming an inner rim. The outer rim consists of different shonkinitic and malignitic rocks. The K-Ar ages obtained for the whole complex vary around 132 Ma.The dunites and clinopyroxenites are characterized by cumulate textures. With increasing modal abundances of clinopyroxene and subordinate phlogopite, the rocks develop to olivine-clinopyroxenite, shonkinite, and malignite with intercumulus potassium feldspar. Mineralogical characterization of the rocks suggests they evolved by fractional crystallization. The highly forsteritic olivines (Fo up to 95) require a melt as magnesian as mg# 87.1, representing ±26 wt.% MgO. The parental melt is likely to be an olivine-, H2O- and K2O-rich picritic liquid of shoshonitic character. Major and trace element systematics show high LILE/LREE and LREE/HFSE ratios indicating the involvement of a subduction zone component in the genesis of these rocks.

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14

Walker, D., S. Jurewicz, and E. B. Watson. "Adcumulus dunite growth in a laboratory thermal gradient." Contributions to Mineralogy and Petrology 99, no. 3 (July 1988): 306–19. http://dx.doi.org/10.1007/bf00375364.

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15

Stepanov, S. Yu, A. V. Kutyrev, E. N. Lepekhina, L. N. Sharpenok, A. V. Antonov, and M. E. Kutyreva. "Age of the Dike Complex in the Dunite “Core” of the Kamenushinsky Clinopyroxenite–Dunite Massif, Ural Platinum Belt, Middle Urals." Geochemistry International 59, no. 6 (June 2021): 559–76. http://dx.doi.org/10.1134/s0016702921060094.

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16

Frost, B. Ronald, Katy A. Evans, Susan M. Swapp, James S. Beard, and Fiona E. Mothersole. "The process of serpentinization in dunite from New Caledonia." Lithos 178 (September 2013): 24–39. http://dx.doi.org/10.1016/j.lithos.2013.02.002.

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17

Mazzucchelli, Maurizio, Giorgio Rivalenti, Daniele Brunelli, Alberto Zanetti, and Elena Boari. "Formation of Highly Refractory Dunite by Focused Percolation of Pyroxenite-Derived Melt in the Balmuccia Peridotite Massif (Italy)." Journal of Petrology 50, no. 7 (November 14, 2008): 1205–33. http://dx.doi.org/10.1093/petrology/egn053.

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18

Coish, R. A., and P. Gardner. "Suprasubduction-zone peridotite in the northern USA Appalachians: evidence from mineral composition." Mineralogical Magazine 68, no. 4 (August 2004): 699–708. http://dx.doi.org/10.1180/0026461046840214.

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AbstractMineral compositions of small peridotite bodies in an Ordovician collision zone of the Vermont Appalachians provide important clues to their tectonic environment of origin. The bodies have been deformed and partially serpentinized under greenschist- to lower amphibolite-facies conditions during the Ordovician and Devonian. Before serpentinization, the peridotite bodies were dunite as shown by their mineral assemblage and by their high MgO, and low Ti and Al whole-rock contents. Despite deformation and metamorphism, remnant olivine and spinel grains occur; their compositions are taken to represent conditions prior to regional metamorphic events. High Mg/(Mg+Fe) in olivine and very high Cr/(Cr+Al) in spinel indicate that the peridotites formed as highly-depleted mantle residues. The compositions are similar to those in harzburgite and dunite from some ophiolites and from fore-arc regions of subduction zones. Accordingly, the southern Vermont peridotites probably formed in a forearc, supra-subduction zone during the Early Palaeozoic. They were subsequently emplaced by obduction of the upper plate of an east-facing subduction complex.

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19

Tessalina, Svetlana G., Kreshimir N. Malitch, Thierry Augé, Victor N. Puchkov, Elena Belousova, and Brent I. A. McInnes. "Origin of the Nizhny Tagil Clinopyroxenite–Dunite Massif, Uralian Platinum Belt, Russia: Insights from PGE and Os Isotope Systematics." Journal of Petrology 56, no. 12 (December 2015): 2297–318. http://dx.doi.org/10.1093/petrology/egv077.

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20

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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21

Snortum, Eric, James M. D. Day, and Matthew G. Jackson. "Pacific Lithosphere Evolution Inferred from Aitutaki Mantle Xenoliths." Journal of Petrology 60, no. 9 (September 1, 2019): 1753–72. http://dx.doi.org/10.1093/petrology/egz047.

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Abstract Highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, Re), major and trace element abundances, and 187Re–187Os systematics are reported for xenoliths and lavas from Aitutaki (Cook Islands), to investigate the composition of Pacific lithosphere. The xenolith suite comprises spinel-bearing lherzolites, dunite, and harzburgite, along with olivine websterite and pyroxenite. The xenoliths are hosted within nephelinite and alkali basalt volcanic rocks (187Os/188Os ∼0·1363 ± 13; 2SD; ΣHSE = 3–4 ppb). The volcanic host rocks are low-degree (2–5%) partial melts from the garnet stability field and an enriched mantle (EM) source. Pyroxenites have similar HSE abundances and Os isotope compositions (Al2O3 = 5·7–8·3 wt %; ΣHSE = 2–4 ppb; 187Os/187Os = 0·1263–0·1469) to the lavas. The pyroxenite and olivine websterite xenoliths directly formed from—or experienced extensive melt–rock interaction with—melts similar in composition to the volcanic rocks that host the xenoliths. Conversely, the Aitutaki lherzolites, harzburgites and dunites are similar in composition to abyssal peridotites with respect to their 187Os/188Os ratios (0·1264 ± 82), total HSE abundances (ΣHSE = 8–28 ppb) and major element abundances, forsterite contents (Fo89·9±1·2), and estimated extents of melt depletion (<10 to >15%). These peridotites are interpreted to sample relatively shallow Pacific mantle lithosphere that experienced limited melt–rock reaction and melting during ridge processes at ∼90 Ma. A survey of maximum time of rhenium depletion ages of Pacific mantle lithosphere from the Cook (Aitutaki ∼1·5 Ga), Austral (Tubuai’i ∼1·8 Ga), Samoan (Savai’i ∼1·5 Ga) and Hawaiian (Oa’hu ∼2 Ga) island groups shows that Mesoproterozoic to Neoproterozoic depletion ages are preserved in the xenolith suites. The variable timing and extent of mantle depletion preserved by the peridotites is, in some instances, superimposed by extensive and recent melt depletion as well as melt refertilization. Collectively, Pacific Ocean island mantle xenolith suites have similar distributions and variations of 187Os/188Os and HSE abundances to global abyssal peridotites. These observations indicate that Pacific mantle lithosphere is typical of oceanic lithosphere in general, and that this lithosphere is composed of peridotites that have experienced both recent melt depletion at ridges and prior and sometimes extensive melt depletion across several Wilson cycles spanning periods in excess of two billion years.

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22

Miller, Hannah M., Lisa E. Mayhew, Eric T. Ellison, Peter Kelemen, Mike Kubo, and Alexis S. Templeton. "Low temperature hydrogen production during experimental hydration of partially-serpentinized dunite." Geochimica et Cosmochimica Acta 209 (July 2017): 161–83. http://dx.doi.org/10.1016/j.gca.2017.04.022.

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23

Govil, Pradip K., and B. L. Narayana. "New Reference Material of Dunite Rock, NGRI-UMR: Preparation and Evaluation." Geostandards and Geoanalytical Research 23, no. 1 (June 1999): 77–85. http://dx.doi.org/10.1111/j.1751-908x.1999.tb00561.x.

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24

Bazylev, B. A., G. V. Ledneva, Ya V. Bychkova, N. N. Kononkova, T. G. Kuz’mina, and T. V. Romashova. "Estimation of the Content and Composition of Trapped Melt in Dunite." Geochemistry International 57, no. 5 (May 2019): 509–23. http://dx.doi.org/10.1134/s0016702919050021.

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25

Jackson, Ian, M. S. Paterson, and J. D. Fitz Gerald. "Seismic wave dispersion and attenuation in Åheim dunite: an experimental study." Geophysical Journal International 108, no. 2 (February 1992): 517–34. http://dx.doi.org/10.1111/j.1365-246x.1992.tb04633.x.

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26

KELEMEN, PETER B. "Reaction Between Ultramafic Rock and Fractionating Basaltic Magma I. Phase Relations, the Origin of Calc-alkaline Magma Series, and the Formation of Discordant Dunite." Journal of Petrology 31, no. 1 (February 1, 1990): 51–98. http://dx.doi.org/10.1093/petrology/31.1.51.

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27

Canil, Dante, Mark Brearley, and Christopher M. Scarfe. "Petrology of ultramafic xenoliths from Rayfield River, south-central British Columbia." Canadian Journal of Earth Sciences 24, no. 8 (August 1, 1987): 1679–87. http://dx.doi.org/10.1139/e87-161.

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One hundred mantle xenoliths were collected from a hawaiite flow of Miocene–Pliocene age near Rayfield River, south-central British Columbia. The massive host hawaiite contains subrounded xenoliths that range in size from 1 to 10 cm and show protogranular textures. Both Cr-diopside-bearing and Al-augite-bearing xenoliths are represented. The Cr-diopside-bearing xenolith suite consists of spinel lherzolite (64%), dunite (12%), websterite (12%), harzburgite (9%), and olivine websterite (3%). Banding and veining on a centimetre scale are present in four xenoliths. Partial melting at the grain boundaries of clinopyroxene is common and may be due to natural partial melting in the upper mantle, heating by the host magma during transport, or decompression during ascent.Microprobe analyses of the constituent minerals show that most of the xenoliths are well equilibrated. Olivine is Fo89 to Fo92, orthopyroxene is En90, and Cr diopside is Wo47En48Fs5. More Fe-rich pyroxene compositions are present in some of the websterite xenoliths. The Mg/(Mg + Fe2+) and Cr/(Cr + Al + Fe3+) ratios in spinel are uniform in individual xenoliths, but they vary from xenolith to xenolith. Equilibration temperatures for the xenoliths are 860–980 °C using the Wells geothermometer. The depth of equilibration estimated for the xenoliths using geophysical and phase equilibrium constraints is 30–40 km.

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Garnier, J., C. Quantin, E. Guimarães, and T. Becquer. "Can chromite weathering be a source of Cr in soils?" Mineralogical Magazine 72, no. 1 (February 2008): 49–53. http://dx.doi.org/10.1180/minmag.2008.072.1.49.

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AbstractAt Niquelândia, Cr extracted from the soil (5,000–9,300 mg.kg-1) is likely the result of the Cr-bearing Fe-oxides compared to the Cr-spinels, showing that low Cr-containing minerals present in the dunite (enstatite, olivine and clay minerals) have been completely dissolved. The chromites, accumulated inside soil profiles, have undergone chemical weathering, leading to a Cr enrichment during soil genesis. Traces of dissolution inside the soil chromites suggest that they can be slowly weathered. In this case chromites could represent a diffuse source of available Cr(III) within the soil profiles.

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29

Zaccarini, F., O. A. R. Thalhammer, F. Princivalle, D. Lenaz, C. J. Stanley, and G. Garuti. "DJERFISHERITE IN THE GULI DUNITE COMPLEX, POLAR SIBERIA: A PRIMARY OR METASOMATIC PHASE?" Canadian Mineralogist 45, no. 5 (October 1, 2007): 1201–11. http://dx.doi.org/10.2113/gscanmin.45.5.1201.

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30

Suhr, G. "Melt Migration under Ocean Ridges: Inferences from Reactive Transport Modelling of Dunite Bodies." Mineralogical Magazine 62A, no. 3 (1998): 1475–76. http://dx.doi.org/10.1180/minmag.1998.62a.3.107.

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31

Rehfeldt, Tatjana, Stephen F. Foley, Dorrit E. Jacob, Richard W. Carlson, and Dave Lowry. "Contrasting types of metasomatism in dunite, wehrlite and websterite xenoliths from Kimberley, South Africa." Geochimica et Cosmochimica Acta 72, no. 23 (December 2008): 5722–56. http://dx.doi.org/10.1016/j.gca.2008.08.020.

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32

Maaløe, S. "The dunite bodies, websterite and orthopyroxenite dikes of the Leka ophiolite complex, Norway." Mineralogy and Petrology 85, no. 3-4 (August 3, 2005): 163–204. http://dx.doi.org/10.1007/s00710-005-0085-5.

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33

Harder, S. "Analysis of elastic symmetry from velocity measurements with application to dunite and bronzitite." Geophysical Journal International 94, no. 3 (September 1, 1988): 469–77. http://dx.doi.org/10.1111/j.1365-246x.1988.tb02269.x.

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Mekhonoshin, A. S., N. D. Tolstykh, M. Yu Podlipsky, T. B. Kolotilina, A. V. Vishnevsky, and Yu P. Benedyuk. "PGE mineralization of dunite-wehrlite massifs at the Gutara-Uda interfluve, Eastern Sayan." Geology of Ore Deposits 55, no. 3 (May 2013): 162–75. http://dx.doi.org/10.1134/s1075701513030021.

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Majumdar, Alik S., Jörn Hövelmann, Christian Vollmer, Jasper Berndt, Sisir K. Mondal, and Andrew Putnis. "Formation of Mg-rich Olivine Pseudomorphs in Serpentinized Dunite from the Mesoarchean Nuasahi Massif, Eastern India: Insights into the Evolution of Fluid Composition at the Mineral–Fluid Interface." Journal of Petrology 57, no. 1 (January 2016): 3–26. http://dx.doi.org/10.1093/petrology/egv070.

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Dygert, Nick, Yan Liang, and Peter B. Kelemen. "Formation of Plagioclase Lherzolite and Associated Dunite–Harzburgite–Lherzolite Sequences by Multiple Episodes of Melt Percolation and Melt–Rock Reaction: an Example from the Trinity Ophiolite, California, USA." Journal of Petrology 57, no. 4 (April 2016): 815–38. http://dx.doi.org/10.1093/petrology/egw018.

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37

Gianola, Omar, Max W. Schmidt, Oliver Jagoutz, Jörg Rickli, Olivier Bruguier, and Oyungerel Sambuu. "The Crust–Mantle Transition of the Khantaishir Arc Ophiolite (Western Mongolia)." Journal of Petrology 60, no. 4 (February 13, 2019): 673–700. http://dx.doi.org/10.1093/petrology/egz009.

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Abstract The crust–mantle transition of the Khantaishir ophiolite in western Mongolia is well exposed. The mantle section shows an up to 4 km thick refractory harzburgitic mantle with local dunite channels and lenses. Towards its top, the mantle is increasingly replaced by discrete zones of pyroxenite, which form a kilometre-wide and hundreds of metres-thick horizon at the contact with the overlying crustal section. The plutonic crustal section is composed of gabbros, gabbronorites, tonalites and minor plagiogranites. The lower part of the crustal section is intercalated with pyroxenite lenses, forming a layered sequence, whereas the upper part is cut by volcanic dykes associated with the overlying basalt–andesitic volcanic section. Most of the ultramafic rocks and gabbronorites show a depletion in high field strength elements and positive anomalies for Sr and Pb, whereas gabbros, tonalites and plagiogranites are enriched in large ion lithophile elements and have slightly enriched rare earth element patterns. Non-modal fractional melting models indicate that the most depleted harzburgites of the ophiolite originated after 20–25% of melt extraction from the mantle. Leached minerals and whole-rocks from the crust–mantle transition of the Khantaishir ophiolite define a Sm–Nd isochron at 540 ± 12 Ma, which is interpreted as the formation age of the crust–mantle transition. Additionally, minerals and whole-rocks display a restricted εNd(t=540 Ma) composition (+3·5 to +7·0) and a large scatter in εSr(t=540 Ma) (–19·8 to +14·2). Clinopyroxenes in the crust–mantle transition rocks indicate that they were in equilibrium with a boninitic-like melt, consistent with the lavas observed in the volcanic section of the ophiolite. It is therefore inferred that the Khantaishir ophiolite represents a slice of an incipient oceanic island-arc formed in a suprasubduction environment.

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Järvinen, Ville, Tapio Halkoaho, Jukka Konnunaho, Jussi S. Heinonen, and O. Tapani Rämö. "Parental magma, magmatic stratigraphy, and reef-type PGE enrichment of the 2.44-Ga mafic-ultramafic Näränkävaara layered intrusion, Northern Finland." Mineralium Deposita 55, no. 8 (December 31, 2019): 1535–60. http://dx.doi.org/10.1007/s00126-019-00934-z.

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AbstractAbout 20 mafic-ultramafic layered intrusions in the northern Fennoscandian shield were emplaced during a widespread magmatic event at 2.5–2.4 Ga. The intrusions host orthomagmatic Ni-Cu-PGE and Cr-V-Ti-Fe deposits. We update the magmatic stratigraphy of the 2.44-Ga Näränkävaara mafic-ultramafic body, northeastern Finland, on the basis of new drill core and outcrop observations. The Näränkävaara body consists of an extensive basal dunite (1700 m thick), and a layered series comprising a peridotitic–pyroxenitic ultramafic zone (600 m thick) and a gabbronoritic–dioritic mafic zone (700 m thick). Two reversals are found in the layered series. The composition of the layered series parental magma was approximated using a previously unidentified marginal series gabbronorite. The parental magma was siliceous high-Mg basalt with high MgO, Ni, and Cr, but also high SiO2 and Zr, which suggests primary magma contamination by felsic crust. Cu/Pd ratio below that of primitive mantle implies PGE-fertility. The structural position of the marginal series indicates that the thick basal dunite represents an older wallrock for the layered intrusion. A subeconomic reef-type PGE-enriched zone is found in the border zone between the ultramafic and mafic zones and has an average thickness of 25 m with 150–250 ppb of Pt + Pd + Au. Offset-type metal distribution and high sulfide tenor (50–300 ppm Pd) and R-factor (105) suggest reef formation by sulfide saturation induced by fractional crystallization. The reef-forming process was probably interrupted by influx of magma related to the first reversal. Metal ratios suggest that this replenishing magma was PGE-depleted before emplacement.

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Stepanov, S. Yu, R. S. Palamarchuk, D. A. Varlamov, A. V. Kozlov, D. A. Khanin, and A. V. Antonov. "Platinum Group Minerals from Veresovka River Deluvial Placer, Veresovoborsky Dunite–Clinopyroxenite Massif (Middle Urals)." Geology of Ore Deposits 61, no. 8 (December 2019): 767–81. http://dx.doi.org/10.1134/s1075701519080117.

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Sklyarov, Eugene V., Angrey V. Lavrenchuk, Valentine S. Fedorovsky, Evgenii V. Pushkarev, Dina V. Semenova, and Anastasia E. Starikova. "Dismembered Ophiolite of the Olkhon Composite Terrane (Baikal, Russia): Petrology and Emplacement." Minerals 10, no. 4 (March 30, 2020): 305. http://dx.doi.org/10.3390/min10040305.

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Dismembered ophiolites in the Early Paleozoic Olkhon terrane, a part of the Baikal collisional belt in the southern periphery of the Siberian craton, occur as fault-bounded blocks of ultramafic and mafic rocks from a few meters to hundreds of meters in size. The ultramafic rocks are mainly dunite–harzburgite peridotites with gradual transitions between the lithologies, as well as moderate amounts of enstatitite, wehrlite, and clinopyroxenite, but no lherzolite. Most peridotites have strongly depleted chemistry and a mineralogy corresponding to the harzburgite type usual for ophiolites of suprasubduction zones (SSZ). The mafic rocks are leuco- to melanocratic gabbros with different relative percentages of clinopyroxene, olivine, and plagioclase, which enclose thin layers and lenses of clinopyroxenite and anorthosite. They bear back-arc basin geochemical signatures, a setting inferred for the Neoproterozoic southern Siberian craton. The gabbroic rocks are of two geochemical groups; most of their trace-element patterns show Ta-Nb minimums and Sr maximums common to suprasubduction zone ophiolites. Judging by the Ol + Opx + Chl + Chr mineral assemblages, the Olkhon peridotites underwent low amphibolite and amphibolite regional metamorphism at 500–650 °C. The occurrence of the ultramafic and mafic bodies is consistent with formation in an accretionary wedge metamorphosed during a collisional orogeny. The mantle and crustal parts of the Olkhon ophiolite suite apparently were incorporated into the terrane during the frontal collision of perio-oceanic structures with the Siberian craton. Then, in a later oblique collision event, they became dismembered by strike-slip faulting into relatively small bodies and fault blocks exposed in the present erosional surface.

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Robins, B. "Dunite magma or ultramafic cumulates? A discussion of Griffin et al. “Intrusion and contamination of high-temperature dunite magma: the Nordre Bumandsfjord pluton, Seiland, Arctic Norway” Contrib. Mineral. Petrol. (2013) 165:903–930." Contributions to Mineralogy and Petrology 166, no. 5 (July 23, 2013): 1539–41. http://dx.doi.org/10.1007/s00410-013-0924-z.

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Pernet-Fisher, John F., Peter H. Barry, James M. D. Day, D. Graham Pearson, Sarah Woodland, Aleksey M. Agashev, Lyudmila N. Pokhilenko, and Nikolay P. Pokhilenko. "Heterogeneous kimberlite metasomatism revealed from a combined He-Os isotope study of Siberian megacrystalline dunite xenoliths." Geochimica et Cosmochimica Acta 266 (December 2019): 220–36. http://dx.doi.org/10.1016/j.gca.2019.07.054.

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43

Okamura, H., S. Arai, and Y. U. Kim. "Petrology of forearc peridotite from the Hahajima Seamount, the Izu-Bonin arc, with special reference to chemical characteristics of chromian spinel." Mineralogical Magazine 70, no. 1 (February 2006): 15–26. http://dx.doi.org/10.1180/0026461067010310.

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AbstractForearc peridotite is generally characterized by low Mg# (= Mg/[Mg + Fe2+] atomic ratio) at a given Cr# (= Cr/[Cr + Al] atomic ratio) of chromian spinel compared to common abyssal peridotite. This may be due to (1) smaller modal abundance of spinel and/or (2) lower equilibrium temperature, for the forearc peridotite. Forearc peridotite has the same amount of spinel as abyssal peridotite, eliminating the first possibility. Spinel in harzburgite and dunite from the Hahajima Seamount at the Izu-Bonin forearc, has a large Cr#, >0.57, and the Mg# is slightly variable towards low values at a given Cr#. The Mg# of spinel cores decreases strongly with a decrease in size. This is due to cooling along with hydration, which gave rise to a compositional variation of Ca-amphibole, from edenitic hornblende (high-temperature) to tremolite (low-temperature) in the Hahajima peridotite. The average two- pyroxene temperature of the Hahajima peridotite, 921°C, is less than that of the abyssal peridotite (1138°C), which is not consistent with a size-dependent Mg# of spinel for the latter. Forearc peridotite has been cooled effectively by H2O released from the subducted slab, causing a small Mg# of their spinels.

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Yaroshevskii, A. A., S. V. Bolikhovskaya, and E. V. Koptev-Dvornikov. "Geochemical structure of the Yoko-Dovyren layered dunite-troctolite-gabbro-norite massif, northern Baikal area." Geochemistry International 44, no. 10 (October 2006): 953–64. http://dx.doi.org/10.1134/s0016702906100016.

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Morgan, Zachary, Yan Liang, and Peter Kelemen. "Significance of the concentration gradients associated with dunite bodies in the Josephine and Trinity ophiolites." Geochemistry, Geophysics, Geosystems 9, no. 7 (July 2008): n/a. http://dx.doi.org/10.1029/2008gc001954.

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MATSUMOTO, Ichiro, and Shoji ARAI. "Petrology of dunite/harzburgite with decimeter-scale stratification in a drill core from the Tari-Misaka ultramafic complex, southwestern Japan." Journal of Mineralogical and Petrological Sciences 96, no. 1 (2001): 19–28. http://dx.doi.org/10.2465/jmps.96.19.

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YUMUL, Graciano P. "The Acoje Block Platiniferous Dunite Horizon, Zambales Ophiolite Complex, Philippines: Melt Type and Associated Geochemical Controls." Resource Geology 51, no. 2 (June 2001): 165–74. http://dx.doi.org/10.1111/j.1751-3928.2001.tb00089.x.

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Andersen, T., E. A. J. Burke, and E. R. Neumann. "Nitrogen-rich fluid in the upper mantle: fluid inclusions in spinel dunite from Lanzarote, Canary Islands." Contributions to Mineralogy and Petrology 120, no. 1 (May 1, 1995): 20–28. http://dx.doi.org/10.1007/s004100050055.

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Bogard, Donald D., and Daniel H. Garrison. "39Ar–40Ar age and thermal history of martian dunite NWA 2737." Earth and Planetary Science Letters 273, no. 3-4 (September 2008): 386–92. http://dx.doi.org/10.1016/j.epsl.2008.07.003.

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Barkov, Andrei Y., Gennadiy I. Shvedov, Andrey A. Nikiforov, and Robert F. Martin. "Platinum-group minerals from Seyba, Eastern Sayans, Russia, and substitutions in the PGE-rich pentlandite and ferhodsite series." Mineralogical Magazine 83, no. 4 (April 12, 2019): 531–38. http://dx.doi.org/10.1180/mgm.2019.16.

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AbstractChromitite zones associated with ultramafic units of the Lysanskiy layered complex of dunite–peridotite–gabbro composition could well represent the primary source for the placers bearing platinum-group minerals (PGM) of the entire drainage of the River Sisim and its tributaries, the rivers Ko and Seyba, eastern Sayans. Alluvial gold present in the placers of River Seyba, as elsewhere in the Sisim Placer Zone, reflects mineralisation during a recent period of tectonic activity. We focus on the PGM in the Seyba suite, and in particular on the attributes of pentlandite enriched in platinum-group-elements (PGE) and the compositionally similar and recently defined ferhodsite, which were trapped in host grains of Os–Ir–Ru alloy. Both minerals formed from small volumes of fractionated Fe–Ni–Cu melt considerably enriched in the PGE. In the Seyba suite, as in several others, the amounts of PGE in ferhodsite exceeds that in pentlandite, which results in a greater proportion of vacancies than in pentlandite.

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