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Journal articles on the topic 'Ultramafics'
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1
Gathania, C. R., A. K. Chattopadhyay, B. Sharma, S. S. Ameta, and A. K. Ghosal. "Occurrence of Ultramafics of Komatiitic Affinity in the Rikhabdev-Dungarpur Belt, Udaipur and Dungarpur Districts, Rajasthan." Journal Geological Society of India 46, no. 6 (1995): 585–94. http://dx.doi.org/10.17491/jgsi/1995/460602.
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Abstract Preliminary study of the ultramafic suite of rocks emplaced concordantly in the Proterozoic supracrustals of the southern Rajasthan (Aravalli Supergroup) indicates their komatiitic nature. Though the diagnostic spinifex texture is not observed in the highly serpentinised and metamorphosed ultramafics, the amygdaloidal structure and the previously reported igneous joints provide textural evidences for the extrusion of the ultramafic lava. The altered ultramafics still retain certain chemical signatures (high MgO and Mg-No., low Ti02, Al2O3and alkalis) of standard komatiites.
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Kutty, T. R. N., S. R. N. Murthy, and G. V. Anantha Iyer. "REE Geochemistry and Petrogenesis of Ultramafic Rocks of Chalk Hills, Salem." Journal Geological Society of India 28, no. 6 (1986): 449–66. http://dx.doi.org/10.17491/jgsi/1986/280603.
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Abstract REE geochemistry of plagioclase-free, plagioclase-bearing and titanoclinohumite-bearing ultramafic suite of Chalk Hills is presented. The rare earth elements are determined by spark source mass-spectrography combined with a preanalytical chemical concentration reaching ± 4 accuracy and 0.01 ppm detection limit. Plagioclase-free ultramafics are 10 times LREE depleted. while HREE abundance is 1-2 times those of chondrite. Since the samples are not serpentinised, these REE patterns are considered to be primary and compare well with those of high temperature peridotites, particularly on CeN-YbN diagram. The plagioclase-bearing ultramafics and the gabbros have LREE contents 4-22 times chondritic, while the HREE varies from 2-12. The REE patterns of ultramafics from the smaller body show uniform increase in (La/Yb)N ratios from 7 to 15. Higher abundance levels of incompatible alkali elements which do not correlate with the MgO contents, may suggest metasomatic introduction of these elements into the smaller body. Petrogenetic modeling, based on partial melting of spinel peridotites as the source rocks with 2 times chondritic abundance, points towards the residual nature of the plagioclase-free ultramafics after extracting 8-10% of the melt. On the other band, the observed REE patterns of the plagioclase-bearing ultramafics and the gabbros not only indicate the absence of rocks more siliceous than syenogabbros but also suggest that they represent compositions of a depleted parent melt from which they originated. Thus the ultramafic association of Chalk Hills is distinctly different from the igneous suites associated with ophiolites and alpine peridotites.
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van der Ent, Antony, Tanguy Jaffré, Laurent L'Huillier, Neil Gibson, and Roger D. Reeves. "The flora of ultramafic soils in the Australia–Pacific Region: state of knowledge and research priorities." Australian Journal of Botany 63, no. 4 (2015): 173. http://dx.doi.org/10.1071/bt15038.
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In the Australia–Pacific Region ultramafic outcrops are both widespread and extensive, covering thousands of km2. Soils derived from ultramafic bedrock impose edaphic challenges and are widely known to host highly distinctive floras with high levels of endemism. In the Australia–Pacific Region, the ultramafics of the island of New Caledonia are famed for harbouring 2150 species of vascular plants of which 83% are endemic. Although the ultramafic outcrops in Western Australia are also extensive and harbour 1355 taxa, only 14 species are known to be endemic or have distributions centred on ultramafics. The ultramafic outcrops in New Zealand and Tasmania are small and relatively species-poor. The ultramafic outcrops in Queensland are much larger and host 553 species of which 18 (or possibly 21) species are endemic. Although New Caledonia has a high concentration of Ni hyperaccumulator species (65), only one species from Western Australia and two species from Queensland have so far been found. No Ni hyperaccumulator species are known from Tasmania and New Zealand. Habitat destruction due to forest clearing, uncontrolled fires and nickel mining in New Caledonia impacts on the plant species restricted to ultramafic soils there. In comparison with the nearby floras of New Guinea and South-east Asia, the flora of the Australia–Pacific Region is relatively well studied through the collection of a large number of herbarium specimens. However, there is a need for studies on the evolution of plant lineages on ultramafic soils especially regarding their distinctive morphological characteristics and in relation to hyperaccumulation.
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Guice, George L., Michael R. Ackerson, Robert M. Holder, et al. "Suprasubduction zone ophiolite fragments in the central Appalachian orogen: Evidence for mantle and Moho in the Baltimore Mafic Complex (Maryland, USA)." Geosphere 17, no. 2 (2021): 561–81. http://dx.doi.org/10.1130/ges02289.1.
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Abstract Suprasubduction zone (SSZ) ophiolites of the northern Appalachians (eastern North America) have provided key constraints on the fundamental tectonic processes responsible for the evolution of the Appalachian orogen. The central and southern Appalachians, which extend from southern New York to Alabama (USA), also contain numerous ultramafic-mafic bodies that have been interpreted as ophiolite fragments; however, this interpretation is a matter of debate, with the origin(s) of such occurrences also attributed to layered intrusions. These disparate proposed origins, alongside the range of possible magmatic affinities, have varied potential implications for the magmatic and tectonic evolution of the central and southern Appalachian orogen and its relationship with the northern Appalachian orogen. We present the results of field observations, petrography, bulk-rock geochemistry, and spinel mineral chemistry for ultramafic portions of the Baltimore Mafic Complex, which refers to a series of ultramafic-mafic bodies that are discontinuously exposed in Maryland and southern Pennsylvania (USA). Our data indicate that the Baltimore Mafic Complex comprises SSZ ophiolite fragments. The Soldiers Delight Ultramafite displays geochemical characteristics—including highly depleted bulk-rock trace element patterns and high Cr# of spinel—characteristic of subduction-related mantle peridotites and serpentinites. The Hollofield Ultramafite likely represents the “layered ultramafics” that form the Moho. Interpretation of the Baltimore Mafic Complex as an Iapetus Ocean–derived SSZ ophiolite in the central Appalachian orogen raises the possibility that a broadly coeval suite of ophiolites is preserved along thousands of kilometers of orogenic strike.
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Singh, M. M., and Vinod K. Singh. "Geochemistry and tectonic setting of the supracrustal rocks from the central part of the Bundelkhand craton, India." Journal of Geoscience, Engineering, Environment, and Technology 4, no. 2-2 (2019): 3. http://dx.doi.org/10.25299/jgeet.2019.4.2-2.2175.
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Supracrustal rocks (mafics and ultramafics) occurs along with banded iron formation, and felsic volcanics around Babina, Dhaura, and Mauranipur linear east-west trends in central part of the Bundelkhand craton represent Archean crust. The mafic and ultramafic rocks geochemically classified into Komatiite and Basaltic Komatiite and have high-Fe Tholeiitic in composition which may relate with the primitive mantle. The major and trace element geochemistry of mafic and ultramafic rocks correspond to hydrated mantle with wedge tectonic sources and ocean ridge geological characteristics.
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Sreckovic-Batocanin, Danica, Dragan Milovanovic, and Kadosa Balogh. "Petrology of the Garnet Amphibolites from the Tejici Village - Povlen Mt., Western Serbia." Annales g?ologiques de la Peninsule balkanique, no. 64 (2002): 187–98. http://dx.doi.org/10.2298/gabp0264187s.
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Different metamorphic rocks discovered near the village of Tejici (Povlen Mt., Western Serbia) represent members of the olistostrome m?lange metamorphosed during the obduction/emplacement of some still hot ultramafic body. They occupy the area of about 2 km2. The garnet amphibolites are of highest metamorphic grade in the area of Tejici and were chosen as the most convenient rocks for determination the pressure-temperature conditions of metamorphism and of ultramafics during their emplacement.
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Nayak, Debajyoti, Pranab Das, and Sagar Misra. "Petrology and Geochemistry of Mesoarchean Sukinda Ultramafics, Southern Singhbhum Odisha Craton, India: Implications for Mantle Resources and the Geodynamic Setting." Minerals 13, no. 11 (2023): 1440. http://dx.doi.org/10.3390/min13111440.
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The Sukinda ultramafic complex in India comprises precisely two areas: Kaliapani (KLPN) and Katpal (KTPL). These areas consist of a sequence of lithotypes, including orthopyroxenite, dunite, serpentinite, and chromitite, displaying a rhythmic layering of rocks. These rocks exhibit a cumulate texture and stand out due to their elevated Mg# (78.43–93.20), Cr (905.40–58,799 ppm), Ni (193.81–2790 ppm), Al2O3/TiO2 (27.01–74.06), and Zr/Hf (39.81–55.24) ratios, while possessing lower TiO2 contents (0.01–0.12 wt%). These ultramafics, characterized by low Ti/V (0.83–19.23) and Ti/Sc (7.14–83.72) ratios, negative anomalies of Zr, Hf, Nb, and Ti in a primitive mantle-normalized spider diagram, indicate that the ultramafics originate from a depleted mantle source. Furthermore, the presence of enriched LREE compared to HREE, a negative Eu anomaly, and enrichment of Th, U, and negative Nb anomalies suggest a subduction setting. The whole-rock geochemical data reveal high levels of MgO, Cr, and Ni, as well as low TiO2 and CaO/Al2O3 ratios and high Al2O3/TiO2 ratios. Moreover, the mineral chemistry data of the ultramafic rocks show high-Mg olivine (Fo 90.9−94.1) in dunite, high-Mg orthopyroxene (En 90.4–90.7) in orthopyroxenite, and high Cr# (0.68–0.82) and low Mg# (0.40–0.54) in chromite, alongside significant Al2O3 (9.93–12.86 wt%) and TiO2 (0.20–0.44 wt%) contents in the melt. Such geochemical characteristics strongly suggest that the Sukinda ultramafic originates from the fractional crystallization of a boninitic parental magma, which is derived from the second-stage melting in a depleted metasomatized mantle source within a supra-subduction zone tectonic setting.
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Firstova, Anna, Georgy Cherkashov, Tamara Stepanova, Anna Sukhanova, Irina Poroshina, and Victor Bel’tenev. "New Data for the Internal Structure of Ultramafic Hosted Seafloor Massive Sulfides (SMS) Deposits: Case Study of the Semenov-5 Hydrothermal Field (13°31′ N, MAR)." Minerals 12, no. 12 (2022): 1593. http://dx.doi.org/10.3390/min12121593.
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The internal structure of Seafloor Massive Sulfides (SMS) deposits is one of the most important and complex issues facing the study of modern hydrothermal ore systems. The Semenov-5 hydrothermal field is a unique area where mass wasting on the slope of the oceanic core complex (OCC) structure exposes the subsurface portion of the deposit and offers an exceptional opportunity to observe massive sulfides that have formed not only on the seafloor but in sub-seafloor zones as well. This paper examines the internal structure of the OCC-related Semenov-5 hydrothermal field along with analysis of the mineralogy and chemistry of different parts of sulfide deposit. The seafloor deposit is comprised of pyrite, marcasite, hematite, goethite, lepidocrocite, rare pyrrhotite, isocubanite and Co-rich pyrite. Sulfide chemistry indicates the prevailing influence of ultramafics on their composition irrespective of the spatial relation with basalt lavas. Sub-seafloor mineralization is associated with ultramafic rocks and is represented by massive and disseminated sulfides. Pyrrhotite, isocubanite, pyrite, chalcopyrite, Co-rich pyrite, quartz with rutile, quarts with hematite and Cr-spinels are fixed in massive subseafloor mineralization. The presence of Cr-spinels as well as a very high Cr content are regarded as indicators of the metasomatic nature of this part of the deposit that had formed as a result of ultramafic replacement. As a result, three zones of a hydrothermal ore-forming system have been described: massive sulfides precipitated from hot vents on the surface of the seafloor, massive sulfides formed due to replacement of ultramafics below the seafloor and disseminated sulfide mineralization-filled cracks in hosted rocks which have formed stockwork around metasomatic massive sulfides. Despite differences in the mineral and geochemical composition of sub-seafloor and seafloor mineralization, all minerals subject to the sample formed as a consequence of fluid circulation in ultramafic rocks and were linked by a common ore-forming process.
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Çina, A. "MINERALOGY OF CHROMITITE, BULQIZA ULTRAMAFIC MASSIF, ALBANIAN OPHIOLITIC COMPLEX." Bulletin of the Geological Society of Greece 43, no. 5 (2017): 2577. http://dx.doi.org/10.12681/bgsg.11665.
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Ultramafic massif of Bulqiza belongs to Eastern Jurassic Albanian ophiolite belt of IAT-BSV- type. This massif is the most important chromite-bearing ore. The mantle ultramafics have extremely refractory nature. This is due to the high partial fusion of upper mantle which is depleted in CaO and Al2 O3 . The chromitite is situated to different parts of ultramafic pile, from bottom Cpx harzburgites up to massive dunites and cumulate ultramafic but the mainly chromite potential belongs to mantle harzburgite –dunite level and to transition dunites partly. The chromite is chiefly of Cr-rich metallurgical type. The atomic ratios of chromite , Fo of olivine and some physical properties of them vary according to the chromitite setting and reflects the evolution of Ol-Sp equilibrium process depended of the chromite concentration, from baren dunitic lenses towards dunite envelops of the ore bodies and the interstitial and inclusions of olivine within chromite grains. Two particular chromite deposits are the Bulqiza- Batra tabular folded ore body and Shkalla, pencil –like ore body.
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Ivanov, K. S., N. V. Vakhrusheva, V. N. Puchkov, P. B. Shiryaev, N. N. Farrakhova, and A. E. Bogomolova. "Unserpentinized harzburgites of the Voikaro-Synyinsky massif of the Polar Urals as the initial source of chromium for the formation of deposits." Doklady Rossijskoj akademii nauk. Nauki o Zemle 516, no. 1 (2024): 382–90. https://doi.org/10.31857/s2686739724050086.
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The composition and age of unserpentinized harzburgites, which are found in the Voikaro-Synyinsky massif in the form of budins and relict bodies in the fields of olivine-antigorite rocks development, have been studied. The structure, compositions of rocks and minerals, as well as the distribution of rare-earth elements and Sm-Nd absolute dating (≈2330 million years) allow us to consider these unserpentinized harzburgites as fragments of the mantle and the earliest formations among the ultramafic Voikaro-Synyinsky massif. The silicates of these harzburgites are characterized by increased chromium content, which in subsequent different processes turns into chromium spinelide. Based on the data obtained, the resources of chromium mobilized during the transformation of primary ultramafics were evaluated.
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Srikantia, S. V., and S. S. Bose. "Archaean Komatiites from Banasandra Area of Kibbanahalli Arm Of Chitradurga Supracrustal Belt in Karnataka." Journal Geological Society of India 26, no. 6 (1985): 407–17. http://dx.doi.org/10.17491/jgsi/1985/260605.
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Abstract The Banasandra Komatiites occur within the Kibbanahalli arm of the Chitradurga supracrustal Belt in Karnataka. They apparently overlie the Bababudan Group and the Peninsular Gneiss and occur in two isolated exposures, (i) east of Birasandra, and (ii) near Kodihalli - Kunikenahalli. Ultramafic rock types include pillowed serpentinites, spinifex-textured komatiite, massive and schistose serpentinite and talc-tremolite-chlorite schist. Certain quartz-antigorite (birbirite ?), quartz-amphibole, and high-magnesian chlorite rocks are also closely associated with the ultramafics. The major element chemistry of the Banasandra komatiites compares with those of Barberton, S. Africa, Munro Township, Canada and of W. Australia. The exact relationship between these komatiites and the Bababudan volcanics is not clear for lack of continuous outcrops. Field evidences point to possible tectonic emplacement.
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Imchen, Watitemsu, Pukrozo Keyho, Meribemo Yanthan, Imomeren Ao, and John K. Angami. "MG-RICH ULTRAMAFICS OF THE NAGA HILLS OPHIOLITE, NAGALAND, INDIA: A POTENTIAL SUBSTITUTE AS BASIC FLUX IN METALLURGICAL INDUSTRIES." Malaysian Journal of Geosciences 6, no. 1 (2022): 45–52. http://dx.doi.org/10.26480/mjg.01.2022.45.52.
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Flux materials are indispensable in iron ore refining process to effectively segregate gangue minerals and to improve other physicochemical properties. Lately, the demand for metallurgical grade flux materials such as limestone and dolomite for iron and steel manufacturing industries in India has surged manifold and depends largely on imports due to its limited resources. MgO-bearing flux has emerged to be a potential alternative to conventional fluxes (limestone and dolomite); though huge resources of Mg-rich ultramafic rocks are available in the Indian subcontinent, their economic utility as metallurgical flux is not fully explored. To evaluate the suitability of flux material in iron and steel industries, Mg-rich ultramafics of the Naga Hills Ophiolite (NHO) have been studied. Major oxides and petro-mineralogical studies have been undertaken to understand the chemical and mineralogical attributes of NHO Mg-rich ultramafics. Results indicate appreciable MgO content (up to 46.7%) barring pyroxenite, with low Al2O3 (< 2 wt%), loss on ignition (< 14 wt%), and Cr2O3 (< 1 wt%) conforming to the chemical specifications set for flux/sinter mix by the major steel producers in India. Fouling index further indicates Mg-based flux of NHO as better quality in contrast to conventional flux materials, albeit alkali content is relatively high. Finer crystals of NHO Mg-rich rocks are added advantage which would readily assimilate in the melt at lower energy. Mg-based flux in iron and steel industries would aid in augmenting productivity with reduced slag volumes at lower cost, energy and pollution.
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Rossetti, P., G. D. Gatta, V. Diella, S. Carbonin, A. Della Giusta, and A. Ferrario. "The magnetite ore districts of the southern Aosta Valley (Western Alps, Italy): a mineralogical study of metasomatized chromite ore." Mineralogical Magazine 73, no. 5 (2009): 737–51. http://dx.doi.org/10.1180/minmag.2009.073.5.737.
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AbstractIn the southern Aosta Valley (Italian Western Alps), several massive magnetite bodies occur within serpentinized ultramafic rocks belonging to the Mesozoic meta-ophiolite nappe. The ultramafic rocks consist of lherzolite with minor dunite bodies and show a high pressure metamorphic overprint. The results of a multi-methodological study, based on optical microscopy, electron microprobe analysis and single-crystal X-ray diffraction, are reported here in order to give new insights into (1) the mineralogy and crystal chemistry of spinels and silicates and (2) the genesis of the massive magnetite bodies. Chromium-rich relict cores inside the magnetite grains suggest a derivation from primary chromite concentrations. The major-element behaviour shows the presence of two chromite types: a Cr2O3-rich (Al2O3-poor) type and a Cr2O3-poor (Al2O3-rich) type. Magnetite ore deposits probably represent the product of transformation from a chromite proto-ore which formed in ultramafic rocks pertaining to an ophiolite suite. The transformation of chromite to magnetite occurred during multiple stages: the pre- metamorphic setting of the ultramafics and the petrographic evidence suggest that metasomatism started before the onset of the alpine metamorphism and was active during the early alpine, eclogite- facies metamorphic overprint related to a subduction process under high fluid activity.
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Favero-Longo, Sergio E., Enrica Matteucci, Mariagrazia Morando, Franco Rolfo, Tanner B. Harris, and Rosanna Piervittori. "Metals and secondary metabolites in saxicolous lichen communities on ultramafic and non-ultramafic rocks of the Western Italian Alps." Australian Journal of Botany 63, no. 4 (2015): 276. http://dx.doi.org/10.1071/bt14256.
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There is a long history of studies on lichens found in ultramafic habitats, but comparisons between lichen communities on different ultramafic lithologies are scant, and potential metabolic adaptations to the multiple edaphic stresses of ultramafic substrates have been widely neglected. The present work is the first to characterise differences in the abundance and structure of saxicolous lichen communities on different ultramafic lithologies (dunite, lherzolite, and serpentinite), analysed in two areas of the Western Alps (NW Italy). Differences between communities on various ultramafic lithologies were observed, including differences between a mafic control (Mg-Al metagabbro); however, factors other than the substrate were observed to drive more remarkable differences between lichen communities on ultramafics of alpine and pre-alpine areas. XRF analyses demonstrated that the mineral composition of different lithologies is reflected by metal contents in crustose lichens, with weathering processes accounting for relative shifts in elemental abundances between rocks and thalli. A thin layer cromatography screening of lichen secondary metabolites (LSMs), which are thought to regulate metal and pH homeostasis in thalli, revealed lithological vicariance among dominant lichen species with different LSM patterns and intraspecific variability in LSM production associated with differences in lithology and location. In particular, the presence or absence of norstictic acid in species or lineages/individuals on the different lithologies, in relationship to concentrations of Fe, Mg, and Ni in lichen thalli, was recognised as a metabolic adaptation to metal stress. Pull-up tests revealed that physical factors such as a differential surface disaggregation may contribute more towards differences observed in lichen abundance on the different lithologies investigated.
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De Castro, Ma Ellenita Gibe, Jenielyn Padrones, and Katrina Boco. "Vegetation diversity as a factor in carbon sequestration and storage: examples from the ultramafic forests in Palawan Island, Philippines." Journal of Degraded and Mining Lands Management 12, no. 2 (2025): 7009–20. https://doi.org/10.15243/jdmlm.2025.122.7009.
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A floristic study was conducted in two ultramafic formations in Palawan Island, selected for their differing land uses, to assess the role of ultramafic forests as a carbon sink based on plant diversity and Soil Organic Carbon (SOC) content. A total of 17 tree species were identified inside an active mining area in Mt. Bulanjao, Rio Tuba, Bataraza, while only 15 tree species in Magarwak, Brgy. Sta. Lourdes, Puerto Princesa City. Palawan Mangkono (Xanthostemon speciosus Merr.), an island endemic species that thrives well in ultramafics, is the most dominant species in Rio Tuba, Bataraza, whereas Putian (Mastixia pentandra Blume) is the dominant species in Puerto Princesa City based on the Important Value Index (IVI). In terms of diversity, both sites exhibited low diversity index values, with Bataraza site having H'=2.232 while Magarwak, Puerto Princesa City had H'=2.286, respectively. Such data implied the alarming rate of species lost in ultramafic forest, primarily attributable to anthropogenic activities. Further analysis of SOC content indicated that Puerto Princesa City's ultramafic soils contained 99.05 t ha-1, while a much lower value of 85.68 t ha-1 at Bataraza was quantified. Considering the combined contribution of vegetation diversity and soil carbon, this study suggests that Puerto Princesa City's ultramafic formations have the potential to sequester atmospheric carbon and may act as a sink. Both the unusual characteristics of ultramafic soils and their existing vegetation contribute to the enhancement of the carbon storage potential of this forest type, although present land use serves as a crucial consideration. These findings underscore the importance of preserving and conserving native metallophytes in the area, making this research a pivotal basis for conservation efforts.
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Yousufi, Atal, Hemayatullah Ahmadi, Alma Bekbotayeva, et al. "Integration of Remote Sensing and Field Data in Ophiolite Investigations: A Case Study of Logar Ophiolite Complex, SE Afghanistan." Minerals 13, no. 2 (2023): 234. http://dx.doi.org/10.3390/min13020234.
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Mafic–ultramafics complexes are crucial for their tectonic implication, upper mantle condition, and for hosting industrial minerals in a region. This study aims to highlight and characterize the mafic–ultramafic rocks of the Logar Ophiolite Complex using the integration of geospatial technology and field data. The spatial distribution of the ophiolitic complex was examined in this study using the mineralogical indices (MI), band ratio (BR), and spectral angle mapper (SAM) methods within the framework of geospatial technology using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data. Additionally, several samples were collected from the identified complexes for validation, petrographic, and mineralogical analyses. Combining geospatial technology and conventional approaches, e.g., field sampling and geological data analysis yields efficient discrimination of mafic–ultramafic rocks with their associated hydrothermal altered minerals. The serpentinization and carbonate processes are predominantly seen along the eastern side of the active fault zone following the detection of ophiolites. Detailed mapping of the ophiolitic complex and associated rocks was achieved using refined mafic index (MI), band ratio 12/14 and 4/8 for rocks and SAM for highlighting the mafic–ultramafic altered minerals, and petrographic analysis of the collected samples. The field works verified the results of the ASTER data. The findings of this study can significantly contribute to detailed tectonic and geologic studies of the detected ophiolites in terms of their emplacement mechanism and ages.
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Jovanović, Slobodan, Eva Kabaš, Nevena Kuzmanović, Ksenija Jakovljević, Snežana Vukojičić, and Dmitar Lakušić. "Phytosociological characteristics of seven poorly known associations of serpentine rocky grassland vegetation of the order Halacsyetalia sendtneri in Serbia." Botanica Serbica 41, no. 2 (2017): 221–47. https://doi.org/10.5281/zenodo.1026525.
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Although it is well known that dry open rocky grassland vegetation on shallow serpentine (ultramafic) soils represents one of the most interesting, highly endemic, and often studied vegetation types, the authors of several detailed studies of Balkan serpentine flora and vegetation suggested that the vegetation cover of Balkan ultramafics needs further exploration due to its heterogeneity. In this article, phytosociological characteristics of seven poorly known associations of grassland communities from the order <em>Halacsyetalia sendtneri</em> are analysed. In order to provide additional descriptions of these communities (with diagnosis and lists of diagnostic, dominant, and constant species), check their phytosociological validity, and confirm their syntaxonomical position, the stands of these communities were compared with 18 associations distributed throughout the area of serpentine outcrops in Bosnia and Herzegovina and Serbia. The results of cluster analysis confirmed that the analysed heretofore poorly known associations in the vegetation of open rocky serpentine grasslands are floristically well-defined.
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Sherafat, Shahzad, Zahra Torkzadeh, and Mohammad Ali Mackizadeh. "Sepiolite occurrence in ultramafics of the North Nain." Iranian Journal of Crystallography and Mineralogy 26, no. 1 (2018): 219–28. http://dx.doi.org/10.29252/ijcm.26.1.219.
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Roy, Abhinaba, and B. K. Bandyopadhyay. "Tectonic Significance of Ultramafic and Associated Rocks Near Tal in the Bijawar Belt, Sidhi District, Madhya Pradesh." Journal Geological Society of India 32, no. 5 (1988): 397–410. http://dx.doi.org/10.17491/jgsi/1988/320504.
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Abstract Serpentinised ultramafic bodies of peridotite-dunite composition occur as solid state intrusions in the Bijawar volcano-sedimentary sequence around Tal in Sidhi district, Madhya Pradesh. The associated basic volcanics and gabbros are predominantly tholeiitic in composition, although a slight enrichment in Na is recognised locally. However, apart from their juxtaposition, there is no petrological or chemical evidence to suggest that the uhramafic and gabbroic rocks were derived from a common magma. The ultramafics represent olivine-pyroxene cumulates, crystallised at depth and subsequently emplaced as crystalline mush (? diapiric intrusion) during the pre- to early-kinematic stage of basin development. This suggests the possible role of a mantle-derived magma to initiate basin depression. Near the cratonic margin of the basin, shelf sediments (orthoquartzite, carbonate-pelletal chert etc.) were deposited over the gneissic basement while the distal facies was mainly a turbidite. The rocks underwent polyphase deformation and low-grade greenschist facies metamorphism. The closing stage of Bijawar was marked by the emplacement of post-tectonic granite and occasional gabbroic diorite near the peripheral zones of the belt.
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Louie, John N., Robert W. Clayton, and Ronan J. LeBras. "Three‐dimensional imaging of steeply dipping structure near the San Andreas fault, Parkfield, California." GEOPHYSICS 53, no. 2 (1988): 176–85. http://dx.doi.org/10.1190/1.1442452.
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Shot gathers from the Parkfield, California, deep crustal seismic reflection line, recorded in 1977 by COCORP, reveal coherent events having horizontal to reverse moveouts. These events were migrated using a multioffset three‐dimensional Kirchhoff summation method. This method is a ray‐equation back projection inversion of the acoustic wave field, which is valid under the Born, WKBJ, and far‐field assumptions. Migration of full‐wave acoustic synthetics, having the same limitations in geometric coverage as the COCORP survey, demonstrates the utility of the imaging process. The images obtained from back projection of the survey data suggest that the Gold Hill fault carries ultramafic rocks from the surface to 3 km depth at a dip greater than 45 degrees, where it joins the San Andreas fault, which may cut through more homogeneous materials at shallow depths. To the southwest, a 2 km Tertiary sedimentary section appears to terminate against a near‐vertical fault. The zone between this fault and the San Andreas may be floored at 3 km by flat‐lying ultramafics. Lateral velocity inhomogeneities are not accounted for in the migration but, in this case, do not seriously hinder the reconstruction of reflectors.
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Distler, V. V., V. V. Kryachko, and I. P. Laputina. "EVOLUTION OF PLATINUM-GROUP PARAGENESES IN ALPINE-TYPE ULTRAMAFICS." International Geology Review 28, no. 9 (1986): 1068–85. http://dx.doi.org/10.1080/00206818609466350.
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Raznitsyn, Yu N. "Exhumation signs of ultramafics in Knipovich Ridge (North Atlantic)." Doklady Earth Sciences 431, no. 2 (2010): 445–47. http://dx.doi.org/10.1134/s1028334x10040070.
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Ramos, Rodrigo Chaves, and Edinei Koester. "Lithogeochemistry of the meta-igneous units from Arroio Grande Ophiolitic Complex, southernmost Brazil." Brazilian Journal of Geology 45, no. 1 (2015): 65–78. http://dx.doi.org/10.1590/23174889201500010005.
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Ophiolites are defined as slices of genetically-related upper mantle serpentinized peridotites and oceanic crustal rocks, tectonically displaced from its primary igneous origin of formation by plate convergence and associated (meta) sedimentary rocks of marine origin. From this premise, a meta-ultramafic-mafic-sedimentary complex (Cr-rich magnesian schists - upper mantle or crustal ultramafic cumulate candidates; epidote amphibolites, metadiorites and metagabbros - oceanic crust candidates; metasedimentary schists, quartzites and marbles - marine sedimentary rocks candidates), located in southeastern Dom Feliciano Belt (southernmost Brazil), started to be interpreted as possible slices of an ophiolitic complex related to the closure of a paleo-ocean during Brasiliano/Pan-African orogenic cycle and was called Arroio Grande Ophiolitic Complex. The present research fills the lack of geochemical data from previous studies and tests the hypothesis of an oceanic setting for the meta-igneous units of this complex from a lithogeochemistry point of view. The meta-ultramafics were interpreted as peridotites (mantle or crustal cumulates) that were subsequently serpentinized (probably in the ocean floor) and posteriorly metasomatized (probably in a continental setting). The meta-mafics were interpreted as oceanic gabbros/basalts formed in a back-arc basin. The results, together with field relationships, rock associations and petrographic evidences, support an oceanic origin for the protoliths of the meta-igneous units. The hypothesis that these rocks represent metamorphosed slices of an ophiolitic complex is still the most reasonable one. This work updates the geologic knowledge of the area and supports discussions about the evolution of Dom Feliciano Belt and Western Gondwana paleocontinent.
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Baidya, Tapan K., S. K. Mondal, V. Balaram, R. Parthasarathy, R. Verma, and P. K. Mathur. "PGE-Ag-Au Mineralization in a Cu-Fe-Ni Sulphide-Rich Breccia Zone of the Precambrian Nuasahi Ultramafic-Mafic Complex, Orissa, India." Journal Geological Society of India 54, no. 5 (1999): 473–82. http://dx.doi.org/10.17491/jgsi/1999/540503.
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Abstract The Precambrian ultramafic-mafic plutonic complex of Nuasahi, Orissa in the Eastern Indian Shield represents at least three suites of magmatic intrusion: (i) an interlayered sequence of enstatitite, websterite (± olivine), dunite, chromitite, harzburgite and orthopyroxenite; (ii) massive gabbroic suite with minor bodies of norite, anorthosite and bands of titaniferous magnetite and (iii) dykes and sills of dolerite and clinopyroxenite. A prominent breccia zone is developed near the interface of the first and second magmatic suites in the eastern part of the complex including the Shankar chromite lode and the ultramafic host of the first suite, and the gabbro-noritic rocks of the second suite. This breccia zone is enriched in Cu-Fe-Ni sulphides and has become the principal site for concentration of PGE, gold and silver. On a whole, Pd dominates over Pt in the sulphide-bearing Shankar chromite lode and the adjacent orthopyroxenite as well as gabbro in this breccia zone. The chromite-sulphide association is the most enriched part for PGE, gold and silver. Ag is positively correlated with Pd. The breccia zone which was developed prior to the gabbroic emplacement into the chromiferous ultramafics. represents a sulphide-rich metasomatic zone leading to maximum concentrations of PGE, Au, Ag in this zone alongwith formation of various sulphides, oxides and silicates. Both Pt and Pd are considerably higher and Ir is lower in the present area than in chromite-sulphide associations from ophiolitic complexes and Alpine-type massifs. Rather, Pt, Pd and Ir values compare better with the chromite-sulphide associations from layered intrusions.
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K, N. Prakash Narasimha, and Kapfo Lhikhrotso. "Petrological and Geochemical Studies of Felsites around Mandya District, Western Dharwar Craton, South India, Karnataka." International Journal of Geology and Earth Sciences 2, no. 1 (2016): 63–76. https://doi.org/10.5281/zenodo.1494817.
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The Dharwar Craton in south India offers unique opportunity to study the natural cross-section of late Archaean continental crust. A preliminary attempt has been made in this study to understand the petrological and geochemical aspects of felsite dykes that are spread around Mandya district in south India. Geologically investigated area is made up of varied assemblages of rock types ranging from gneiss, ancient supracrustals of Sargur group, Peninsular gneiss, ultramafics, meta-ultramafites, amygdaloidal metabasalt and pillowed/BIF, granodorite, amphibolite and to younger intrusives of Neo-proterozoic age. Felsites in alternation with pegmatites are also exposed. Quartzo-feldspathic veins traverses the felsites at places and felsite with large phenocryst of feldspar are also found. At places felsites are highly jointed and the joint plane trend in E-W direction. Petrographic study shows that felsites are aphanitic and porphyritc in texture. The field and petrographic studies coupled with chemistry data suggest that the felsites dykes of the study area have evolved from a complex crystallization history and are formed in a volcanic arc granitic environment. The concentration of uranium up to 7.1 ppm indicates the potentiality of felsites for the occurrence of radioactive elements.
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Corvò, Stefania, Antonio Langone, José Alberto Padrón-Navarta, Andrea Tommasi, and Alberto Zanetti. "Porphyroclasts: Source and Sink of Major and Trace Elements During Deformation-Induced Metasomatism (Finero, Ivrea-Verbano Zone, Italy)." Geosciences 10, no. 5 (2020): 196. http://dx.doi.org/10.3390/geosciences10050196.
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Petrographic and geochemical data for mylonites from a metric-scale shear zone in mantle peridotites from the Finero massif (Southern Alps) record large mineralogical and geochemical modifications compared to surrounding coarse-grained ultramafic rocks, which were pervasively deformed in presence of hydrous melts. The mylonites are composed by olivine and orthopyroxene and, less frequently, clinopyroxene, phlogopite, and pargasite porphyroclasts enclosed in a fine-grained matrix of phlogopite and olivine, with subordinate amounts of orthopyroxene, clinopyroxene, pargasite, and chromite. P-T estimates indicate that deformation occurred under granulite- to upper-amphibolite facies conditions. Field relationships and U-Pb dating indicate that the shear zone was active during Lower Jurassic and/or later, in an extensional setting at the western margin of the Adria plate, which led to the opening of the Alpine Tethys. The major and trace element composition of the porphyroclasts in the mylonites significantly differ from those in the hosting coarse-grained ultramafics. Porphyroclasts were chemically active during deformation acting as source (diffusion-out) or sink (diffusion-in) for some trace elements. The chemical modifications were promoted by the interaction with aqueous fluids and the composition varied from mantle- (enriched in Ni, Co, Li, Na, REE, Y, and Sr) to crustal-derived (enriched in Zn, K, Al, Ti, and Fe).
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D'Antonio, M., and M. B. Kristensen. "Serpentine and brucite of ultramafic clasts from the South Chamorro Seamount (Ocean Drilling Program Leg 195, Site 1200): inferences for the serpentinization of the Mariana forearc mantle." Mineralogical Magazine 68, no. 6 (2004): 887–904. http://dx.doi.org/10.1180/0026461046860229.
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AbstractSerpentine minerals and brucite in ultramafic rocks from the South Chamorro Seamount were characterized chemically to investigate the serpentinization of the Mariana forearc mantle. Relict primary minerals of the serpentinites are olivine, enstatite and minor Cr-spinel and diopside. The secondary minerals are mostly serpentine and brucite with minor magnetite. The serpentine minerals, mostly lizardite and chrysotile, display large compositional variations. Al2O3 and Cr2O3 contents depend generally upon the nature of the primary mineral from which the serpentine was derived. Both serpentine minerals and brucite exhibit wide Mg, Fe and Mn substitution: the Mg# ranges are 95.1–77.2 and 88.9–60.8, respectively. These mineralogical and chemical features allowed us to estimate an upper temperature limit for serpentinization of ∼200–300°C, in agreement with recent thermal models which suggest that the serpentinized mantle wedge of the Izu-Bonin-Mariana subduction zone is cold. The high degree of serpentinization (40–100%, average >75%), and the serpentine + brucite paragenesis of these ultramafics imply that the Mariana forearc mantle has a significantly reduced density and strength down to ∼30 km, which provides a driving mechanism for serpentinite diapirism. Pervasive serpentinization of the forearc by fluids released from the décollement zone also explains the low seismicity of the Izu-Bonin-Mariana subduction zone.
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Slabunov, A. I., A. A. Shchipansky, V. S. Stepanov, and I. I. Babarina. "A tectonic remnant of the mesoarchean oceanic lithosphere in the Belomorian Province, Fennoscandian Shield." Геотектоника, no. 2 (April 17, 2019): 46–71. http://dx.doi.org/10.31857/s0016-853x2019246-71.
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The results of the detailed geological mapping, coupled with the isotope-geochemical study of a metamorphosed mafic-ultramafic complex known as the Central Belomorian Belt located in the Belomorian province of the Fennoscandian Shield, are reported.
 The protholith of the complex is ~ 2.9—3.1 Ga old. It has been subjected to two 2.87 and 1.87 Ga structural-metamorphic reworking. This complex is one of the oldest in the Belomorian Province.
 We present several lines of evidence showing that these lithologies constitute a tectonic remnant of the Mesoarchean oceanic lithosphere, rather than any other mafic-ulramafic complex from the other geodynamic settings. The Central-Belomorian high grade mafic-ultramafics reveal a clear geochemical coherency, which implies their genetic relationships. Their mafic protholiths stem from the partial melting of a mantle peridotite protholith. The petrologic modelling has shown that primary melts were formed in the garnet lherzolite field at a pressure of 3.5–3.8 GPa at ambient mantle potential temperatures of 1520–1550 °С which led to an emergence of ~ 25–30 thick oceanic crust. The available geochemical data suggest that the complex was formed at the initial stage of subduction. It marks the start of early continental crust-forming processes in the Belomorian Province.
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Ghaderian, S. M., and A. J. M. Baker. "Geobotanical and biogeochemical reconnaissance of the ultramafics of Central Iran." Journal of Geochemical Exploration 92, no. 1 (2007): 34–42. http://dx.doi.org/10.1016/j.gexplo.2006.06.002.
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Groppo, Chiara, Caterina Rinaudo, Simona Cairo, Daniela Gastaldi, and Roberto Compagnoni. "Micro-Raman spectroscopy for a quick and reliable identification of serpentine minerals from ultramafics." European Journal of Mineralogy 18, no. 3 (2006): 319–29. http://dx.doi.org/10.1127/0935-1221/2006/0018-0319.
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TENTHOREY, E. A., J. G. RYAN, and E. A. SNOW. "Petrogenesis of sapphirine‐bearing metatroctolites from the Buck Creek ultramafic body, southern Appalachians." Journal of Metamorphic Geology 14, no. 2 (1996): 103–14. http://dx.doi.org/10.1046/j.1525-1314.1996.05793.x.
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The Buck Creek ultramafic body, North Carolina, includes aluminous lenses that have been described as troctolites. These lenses preserve mineral assemblages which record several different stages of metamorphism. The first stage is characterized by anhydrous reactions between olivine and plagioclase to produce coronas of orthopyroxene+ clinopyroxene/spinel symplectite. Thermo barometric results indicate minimum pressures of c. 6 kbar and c. 800 oC. Sapphirine replaces spinel in some clinopyroxene symplectites, and occurs as anhedral grains within amphibole, observations which in combination suggest peak metamorphic conditions of c. 9‐10 kbar and c. 850 oC. Sapphirine‐bearing hydrous assemblages formed at the expense of the coronas, indicating a second metamorphic episode involving deeper burial, deformation and hydration. Schistose rocks from the margins of the lenses are composed of anorthite+amphibole+margarite+corundum, and probably record a later, lower P‐T event. Whole rock analyses for the Buck Creek lenses suggest an accumulate protolith of magnesian olivine and calcic plagioclase. Trace element data for the troctolites are consistent with data for adjacent amphibolites in suggesting that the Buck Creek mafic and ultramafic cumulates crystallized from magmas derived from a mantle source similar to that which produces modern intraplate or rift‐related basalts. We propose that the Buck Creek ultramafics represent basal cumulates(± uppermost mantle) from ocean crust formed in a marginal basin in the latest Precambrian. Subduction‐induced burial to at least 18 km under dry conditions induced corona formation. Collisional events of the Taconic orogeny thrust the Buck Creek rocks into the orogenic pile to at least 30 km depth and hydrated them along zones of weakness, locally producing P‐T ‐PH2O conditions appropriate for formation of sapphirine and hydrated assemblages, but still preserving some dry symplectites.
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Karetnikov, A. S. "Paleomagnetism of ultramafics from the Konder Massif and its age assessment." Russian Journal of Pacific Geology 3, no. 6 (2009): 530–47. http://dx.doi.org/10.1134/s1819714009060025.
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Petrov, Petko. "Millerite from the Madan ore field." Review of the Bulgarian Geological Society 84, no. 3 (2023): 67–69. http://dx.doi.org/10.52215/rev.bgs.2023.84.3.67.
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Millerite is discovered in samples from Krushev Dol and Mogilata deposits in the Madan ore field. It was found in two associations different in appearance and mineral composition. One of them is with light green ferrodolomite, and the other with bright green mariposite (chromium-bearing phengite). Only cobalt and iron are detected as impurity elements in some analyses. They are in small concentrations (below 0.01 apfu). The Ni/S ratio is 0.95. The nickel source is associated with bodies of serpentinized ultramafics cut by ore-bearing veins.
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Lasheen, El Saeed R., Gehad M. Saleh, Farrage M. Khaleal, and Mamdooh Alwetaishi. "Petrogenesis of Neoproterozoic Ultramafic Rocks, Wadi Ibib–Wadi Shani, South Eastern Desert, Egypt: Constraints from Whole Rock and Mineral Chemistry." Applied Sciences 11, no. 22 (2021): 10524. http://dx.doi.org/10.3390/app112210524.
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This contribution deals with new geology, petrography, and bulk-rock/mineral chemistry of the poorly studied ultramafics of Wadi Ibib–Wadi Shani (WI–WS) district, South Eastern Desert, Egypt. These ultramafics are dismembered ophiolitic rocks that can be subdivided into serpentinites and serpentinized peridotites. Primary minerals such as olivine and pyroxene are absent in serpentinites, but relics of them occur in serpentinized peridotites. Pseudomorph after olivine is indicated by common hourglass textures with less mesh, whilst schistose bastites reflect a pyroxene pseudomorph. Chromite can be subdivided into Cr-spinel and Al-spinel. Cr-spinel ranges from chromite to magnesochromite in composition, whereas Al-spinel belongs to the spinel field. Cr-spinel includes YCr (Cr/(Cr+Al+Fe+3), YAl (Al/(Al+Cr+Fe+3), and YFe+3 (Fe+3/(Fe+3+Al+Cr), similar to forearc peridotite, whilst Al-spinel is more similar to abyssal peridotite, and may be formed during inanition of subduction processes in proto forearc environments. The main secondary minerals are tremolite, talc, and chlorite—which is subdivided into pycnochlorite and diabantite—and their temperature ranges from 174 to 224 °C. The examined rocks had undergone high partial melting degrees (>25%), as indicated by the Cr# of their unaltered cores (Cr-spinel, >0.6), whole rocks (Al2O3, SiO2, CaO, and MgO), trace and REEs, depleted Na2O, Al2O3, and Cr2O3 of clinopyroxene, and high forsterite content ((Fo = 100 Mg/Mg + Fe), av. 95.23 mol%), consistent with forearc settings.
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Roy, A., A. Sarkar, S. K. Bhattacharya, H. Ozaki, and M. Ebihara. "Rare Earth Element Geochemistry of Selected Mafic-Ultramafic Units from Singhbhum Craton: Implications to Source Heterogeneity." Journal Geological Society of India 50, no. 6 (1997): 717–26. http://dx.doi.org/10.17491/jgsi/1997/500607.
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Abstract Modelling ofREE data indicates that while mafic rocks of Dhanjori Group are partial melting products of a spinel Iherzolite source, Dalma ultrabasics are the residue after the melt-extraction from an original garnet lherzolite rock. Ultramafics of Newer dolerite dykes indicate either derivation by mantle meta somatism or effect of post magmatic serpentinisation. REE data in conjunction with the available geochronological data suggest that significant mantle heterogeneity existed over relatively smaller distances (~100 km) even during Proterozoic and that the mantle evolved in a non-uniform manner with distinct localised processes.
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Sinha, K. K., N. Krishna Rao, V. L. Shah, and T. S. Sunilkumar. "Stratigraphic Succession of Precambrian of Singhbhum: Evidence from Quartz Pebble Conglomerate." Journal Geological Society of India 49, no. 5 (1997): 577–88. http://dx.doi.org/10.17491/jgsi/1997/490512.
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Abstract Though the stratigraphic succession in the Precambrian of Singbhum-Orissa region of the Indian shield given by Saba et al. is widely accepted, there are several contentious issues whieh have been hotly debated over the years. The occurrence of uraninite and pyrite bearing quartz-pebble conglomerate at the base of Iron Ore Group (lOG) as well as the Dhanjori Group has indicated the necessity for a revision in the stratigraphic succession in view of the temporal significance of such conglomerate the world over. The conglomerate contains a significant population of zircon, chromite and shows a typical minor and trace element composition. The zircon has morphometric properties similar to those found in several members of the Singhbhum Granite Complex. The presence of detrital chromite and high Cr content indicate the occurrence of older mafics/ultramafics in the provenance along with the Singhbhum Granite Complex. It is suggested that some mafic and ultramafic members presently grouped within the IOG may represent such "older greenstones". The IOG as well as the Dhanjori Group with basal QPC horizon lie over a basement of Singhbhum Granite-Greenstone Complex. From available evidences it is surmised that both IOG sensu stricto (the BIF sequence and associated ferruginous cherts. greywackes and acid-intennediate volcanics) and the Dhanjori Group represent late Archaean (2500-3000 Ma) supracrustals and hence are nearly coeval. The Singhbhum Group north of the shear zone represents early Proterozoic supracrustals.
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Som, S. K., R. Joshi, P. K. Roy, and M. M. Mukherjee. "Morphotectonic Evolution of the Laterite Profiles over Sukinda Ultramafics, Jaipur District, Orissa." Journal Geological Society of India 52, no. 4 (1998): 449–56. http://dx.doi.org/10.17491/jgsi/1998/520408.
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Abstract Sukinda ultramafic field of Jajpur district, Orissa is capped by thick lateritic duricrust. Two generations of laterite are inferred in the studied area. The older laterite (in situ) is capped by transported laterite (younger). The entire area is divided into two subareas (A1 and A2) Physiographically, three terraces are identified in A1 area, of which, the oldest one (T3) comprises of insitu lateritic hard crust. The other two terraces (T2 and T1) are made up of valley fill deposits, which are later lateritised. The area A2 shows the lateral continuity of T3 terrace of A1 area along with valley fill deposit of T1 terrace and the absence of T2 terrace. Drainage analysis show the A1 area is structurally more disturbed than A2 area. Correlation of geomorphological evolution and lateritisation indicates three stages of development in the A1 area. Lateritisation was initiated on a comparatively flat ground (T3 terrace) and subsequent destabilisation of the area developed the younger terraces (T2 and T1) with the modification of older laterite profile.
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Ivanov, K. S., A. A. Krasnobaev, V. N. Smirnov, and S. V. Berzin. "Zircon geochronology of mantle ultramafics from the Klyuchevskoi massif of the Urals." Doklady Earth Sciences 452, no. 2 (2013): 983–87. http://dx.doi.org/10.1134/s1028334x13100012.
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Wah, Wah Khine, and Than Oo Than. "Serpentine and Serpentinization of Ultramafics, Mwe Taung Area, Kalay Township, Chin State." Dagon University Research Journal Vol.8, no. 2018 (2019): Pg.443–460. https://doi.org/10.5281/zenodo.3561240.
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Cooper, Alan F., Richard C. Price, and Anthony Reay. "Geochemistry and origin of a Mesozoic ophiolite: the Pounamu Ultramafics, Westland, New Zealand." New Zealand Journal of Geology and Geophysics 61, no. 4 (2018): 444–60. http://dx.doi.org/10.1080/00288306.2018.1494005.
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Christiansen, F. G. "Deformation fabric and microstructures in ophiolitic chromitites and host ultramafics, Sultanate of Oman." Geologische Rundschau 74, no. 1 (1985): 61–76. http://dx.doi.org/10.1007/bf01764570.
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Shestopalova, O., and V. Drukarenko. "Magneto-mineralogical characteristics of mafite-ultramafites of the Middle Bug River area and Holovaniv suture zone of the Ukrainian Shield (overview)." Geofizicheskiy Zhurnal 44, no. 6 (2023): 144–61. http://dx.doi.org/10.24028/gj.v44i6.273648.
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Mafites and ultramafites manifest in the magnetic field as significant magnetic anomalies due to the high content of magnetite, titanomagnetite and iron-magnesium silicates. Studying the mineralogy and magnetic properties of Archean rocks formed deep in the lower crust and uplifted to the surface allows to understanding the sources of magnetic anomalies. Such rocks are known in the Ukrainian shield, in particular in the Middle Bug River region and in the Holovaniv suture zone (HSZ). We consider mafic-ultramafic assemblages of the rocks of this region, their mineral composition and magnetic characteristics, manifestations in the magnetic field, and the distribution of magnetic minerals. Several mafic-ultramafic associations of different ages, composed of effusive, sedimentary-effusive and intrusive formations, are recognized for the area the Pobuzkiy ore mining region. Most of them were transformed intensively by metamorphism of granulite (to eclogite) facies and by intense tectonic and diaphoretic processes. The main volcanics and volcanogenic-sedimentary rocks belong to the Tivriv stratum of the Paleoarchean Dniester-Bug and Neoarchaean Bug series. Mantle rocks were the protolith of the Tivriv stratum, which are similar in composition to oceanic basalts. The Pavliv stratum is considered as a part of the Dniester-Bug series. It is composed mainly of two-pyroxene crystal schists (sometimes amphibolized, often with significant magnetite content (up to 10 %)), magnetite-orthopyroxene crystal schists, and bodies of ferruginous quartzites. Both series contain gneiss complexes, as well as bodies of basite-hyperbasites. Mafic rocks are mainly represented by hornblende-pyroxene crystal schists and amphibolites. Ultramafite and mafit-ultramafite intrusive bodies were mapped in the central and northern parts of the HSZ where they are presented by rocks of the hyperbasite and gabbro-peridotite formations. The Holovaniv block of the HSZ is spatially coincident with the Holovaniv gravitational maximum and magnetic anomalies, which are probably caused by the rooting of mafit-ultramafits from the upper mantle along deep fault zones. Magnetic sources with increased magnetization were identified within the district of Haivoron. They are associated with pyroxene schists, gneisses, coarse-grained pyroxene schists, and ferruginous quartzites. The high values of magnetic parameters of the rocks of the Haivoron-Zavallya region are explained by the presence of eulysites and magnetite-hypersthene crystal schists. Within the area of occurence of charnockite-enderbite rocks, the magnetic field with increased intensity and a large-mosaic structure is observed. Differentiation of the magnetic properties of the rocks of the upper part of the Earth’s crust, the shape and low power of the sources indicate their possible primary magmatic formation in the form of massifs and dykes with further metamorphic transformations. Magnetite is the main magnetic mineral of mafite-ultramafites according to thermomagnetic analysis and ore microscopy. Several generations of magnetite are observed. Early generations (reliably magmatic) are present in the dark-colored minerals as point inclusions and emulsion discharges along fissures (disintegration structures of solid solutions). The increase of the amount of magnetite in all types of rocks is associated with superimposed secondary transformations. Redistribution of iron occurs in the recrystallization zones with the formation of clusters of secondary coarse-grained magnetite. According to the hypothesis, the magnetite of ferruginous quartzites has metamorphic origin, while the origin of the magnetite of iron-carbonate and iron-siliceous formations is a controversial issue. It depends on the determination of the genesis of the original substance.
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Spry, Paul G., and Erich U. Petersen. "Zincian högbomite as an exploration guide to metamorphosed massive sulphide deposits." Mineralogical Magazine 53, no. 370 (1989): 263–69. http://dx.doi.org/10.1180/minmag.1989.053.370.15.
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AbstractZincian högbomite (ZnO 3.5–10.5wt.%) occurs as an accessory phase in garnet quartzite that is intimately associated with the Broken Hill and Black Mountain Cu-Pb-Zn-Ag deposits, Aggeneys, South Africa. Högbomite coexists with a number of minerals including quartz, gahnite, sillimanite, sphalerite, pyrrhotine, pyrite, magnetite, and ilmenite, suggesting that högbomite may have formed by sulphidation and oxidation reactions. Such reactions may account for the high Zn content of högbomite. Where associated with metamorphosed massive sulphide deposits högbomite is enriched in Zn relative to that found in ultramafics, Fe-Ti deposits, Fe ores, aluminous metasediments, and skarns. This enrichment in högbomite constitutes a potential exploration guide for metamorphosed massive sulphide deposits.
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Fernando, Edwino, Marilyn Quimado, and Augustine Doronila. "Rinorea niccolifera (Violaceae), a new, nickel-hyperaccumulating species from Luzon Island, Philippines." PhytoKeys 37 (May 9, 2014): 1–13. https://doi.org/10.3897/phytokeys.37.7136.
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A new, nickel-hyperaccumulating species of <i>Rinorea</i> (Violaceae), <i>Rinorea</i> <i>niccolifera </i>Fernando, from Luzon Island, Philippines, is described and illustrated. This species is most similar to the widespread <i>Rinorea bengalensis </i>by its fasciculate inflorescences and smooth subglobose fruits with 3 seeds, but it differs by its glabrous ovary with shorter style (5 mm long), the summit of the staminal tube sinuate to entire and the outer surface smooth, generally smaller leaves (3–8 cm long × 2–3 cm wide), and smaller fruits (0.6–0.8cm diameter). <i>Rinorea niccolifera </i>accumulates to >18,000 µg g-1 of nickel in its leaf tissues and is thus regarded as a Ni hyperaccumulator.
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Trettin, H. P. "Pearya: a composite terrane with Caledonian affinities in northern Ellesmere Island." Canadian Journal of Earth Sciences 24, no. 2 (1987): 224–45. http://dx.doi.org/10.1139/e87-025.
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In Ellesmere Island, the Canadian Shield and Arctic Platform are flanked on the northwest by the lower Paleozoic Franklinian mobile belt, which comprises an unstable shelf (miogeocline) and a deep-water basin, divisible into an inner sedimentary belt and an outer sedimentary–volcanic belt. Both are tied to the shelf by interlocking facies changes, but additional exotic units may be present in the outer belt.Pearya, bordering the deep-water basin on the northwest, is divisible into four successions. Succession I comprises sedimentary and(?) volcanic rocks, deformed, metamorphosed to amphibolite grade, and intruded by granitic plutons at 1.0–1.1 Ga. Succession II consists mainly of platformal sediments (carbonates, quartzite, mudrock), with smaller proportions of mafic and siliceous volcanics, diamictite, and chert ranging in age from Late Proterozoic (Hadrynian) to latest Cambrian or Early Ordovician. Its concealed contact with succession I is tentatively interpreted as an angular unconformity. Succession III (Lower to Middle Ordovician?) includes arc-type and ocean-floor volcanics, chert, mudrock, and carbonates and is associated with fault slices of Lower Ordovician (Arenig) ultramafic–mafic complexes–possibly dismembered ophiolites. The faulted contact of succession III and the ultramafics with succession II is unconformably overlapped by succession IV, 7–8 km of volcanic and sedimentary rocks ranging in age from late Middle Ordovician (Blackriverian = early Caradoc) to Late Silurian (late Ludlow?). The angular unconformity at the base of succession IV represents the early Middle Ordovician (Llandeilo–Llanvirn) M'Clintock Orogeny, which was accompanied by metamorphism up to amphibolite grade and granitic plutonism. Pearya is related to the Appalachian–Caledonian mobile belt by the Grenville age of its basement, the age of its ultramafic–mafic complexes, and evidence for a Middle Ordovician orogeny, comparable in age and character to the Taconic. By contrast, the Franklinian mobile belt has a Lower Proterozoic (Aphebian) – Archean basement and was not deformed in the Ordovician. Stratigraphic–structural evidence suggests that Pearya was transported by sinistral strike slip as three or more slices and accreted to the Franklinian deep-water basin in the Late Silurian under intense deformation. The inferred sinistral motion is compatible with derivation from the northern Caledonides.
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Eskandari, Amir, Mohsen Hosseini, and Eugenio Nicotra. "Application of Satellite Remote Sensing, UAV-Geological Mapping, and Machine Learning Methods in the Exploration of Podiform Chromite Deposits." Minerals 13, no. 2 (2023): 251. http://dx.doi.org/10.3390/min13020251.
Full textAbstract:
The irregular and sporadic occurrence of chromite pods in podiform chromite deposits (PCD), especially in mountainous terranes with rough topography, necessitates finding innovative methods for reconnaissance and prospecting. This research combines several remote sensing methods to discriminate the highly serpentinized peridotites hosting chromite pods from the other barren ultramafic and mafic cumulates. The case study is the area of the Sabzevar Ophiolite (NE Iran), which hosts several known chromite and other mineral deposits. The integration of satellite images [e.g., Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite sensor, Landsat series, and Sentinel-2] coupled with change detection, band rationing, and target detection algorithms [including the Spectral Angle Mapper (SAM)] were used to distinguish potential lithological units hosting chromites. Results have been verified by an initial on-field checking and compared with the high-resolution (GSD ~6 cm) orthomosaic images obtained by the processing of photographs taken from an Unmanned Aerial Vehicle (UAV) at a promising area of 35 km2. The combination of visual interpretation and supervised classification by machine learning methods [Support Vector Machine (SVM)] yielded the production of a geological map, in which the lithological units and structures are outlined, including the crust-mantle transition zone units, mafic cumulates, crosscutting dykes, and mantle sequences. The validation of the results was performed through a second phase, made up of field mapping, sampling, chemical analysis, and microscopic studies, leading to the discovery of new chromite occurrences and mineralized zones. All ultramafic units were classified into four groups based on the degree of serpentinization, represented by the intensity of their average spectral reflectance. Based on their presumed protolith, the highly serpentinized ultramafics and serpentinites were classified into two main categories (dunite or harzburgite). The serpentinite with probable dunitic protolith, discriminated for a peculiar Fe-rich Ni-bearing lateritic crust, is more productive for chromite prospecting. This is particularly true at the contact with mafic dykes, akin to some worldwide chromite deposits. The results of our work highlight the potential of multi-scale satellite and UAV-based remote sensing to find footprints of some chromite mineral deposits.
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Salve, Vinay V., and Durga P. Mohanty. "Structural Analysis and Petrography of High-Grade Gneisses and Associated Mafic / Ultramafic Dikes Around Salem, Southern India." Journal of Geosciences Research 9, no. 1 (2024): 1–8. http://dx.doi.org/10.56153/g19088-023-0165-45.
Full textAbstract:
Southern Granulite Terrane (SGT) of India preserves extensive high-grade granulite facies rocks of Archaean and Proterozoic age. The SGT is divided into number of blocks by several suture/shear zone. Structural investigations on the basement gneisses and younger mafic/ultramafic dikes have been carried out within the Salem block which is part of Northern Granulite Block (NGB), north of the Cauvery Suture Zone (CSZ). The present work emphasizes various scale fold styles and other structural patterns of the area, which includes regionally metamorphosed high-grade rocks as basement for the multiple ultramafic intrusions to the north of Cauvery Suture Zone (CSZ) which highlights the finite strain geometry, complex deformation pattern and high-grade metamorphism. Structural map of the study area is prepared showing two generations of folding, namely F1 whose axial trend is NE-SW, subparallel with general trend of gneissic foliation and are tight isoclinal folds while F2 which are open folds with axial trend NW-SE.E-W structural cross section across the foliation planes, characterizes antiformal and synformal fold patterns of the basement due to varying dip directions which also reflects type-3 interference pattern of folding. Mesoscopic scale shear zones of dextral kinematics in response to E-W collision during Paleo-Meso Archean time, delta type porphyroclasts, S-C fabrics with the dextral movement of CSZ system, Riedel shear, thrust imbricates implying duplex structures, rotation of mafic boudins along shear zones are the most prominent ductile structural features of this area. Brittle structures like different sets of cross cutting joints and faults indicate younger deformation as well. Petrography of major lithologies has classified them into amphibolite gneiss, migmatite gneiss, charnockites, granulites and mylonites as basement rocks to the younger pyroxenite intrusions. Typical textures like, perthite, granulose, reaction rims, sieve textures and microstructures like S-C fabrics, kink bands, rotated porphyroclasts, etc are observed within the basement rocks. Coarse grained textures with fractured porphyroclasts of garnets indicating the water interactions and retrogradations within the granulite facies rocks. Reaction rims observed in charnockites and granulites are indicative of retrogression during shearing. The coarse grained cummulate nature of pyroxenites neither represent deformation nor metamorphism. Keywords: Southern Granulite Terrane, Salem, Structural Analysis, Mafic/Ultramafics, Dikes, Petrography
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SKARPELIS, N. "Geodynamics and evolution of the Miocene mineralization in the Cycladic - Pelagonian belt, Hellenides." Bulletin of the Geological Society of Greece 34, no. 6 (2002): 2191. http://dx.doi.org/10.12681/bgsg.16862.
Full textAbstract:
The paper aims to provide a sound account of the type of Miocene mineralisations in the Cycladic – Pelagonian belt and their relationship with the geodynamic evolution of the area. Skarn and manto types, epithermal precious and base metals mineralisation, and vein magnesite in ultramafics are associated to distinct stages of the geodynamic evolution of the belt. Extensional tectonics favoured their generation. Late stages of extensional tectonics resulted in the formation of vertical to subvertical NW-SE trending fault zones, which were then used as conduits for ascending hydrothermal fluids. The relationship between the geodynamics and the metallogenetic evolution of the belt is discussed on the basis of available data on the geology of four critical areas: Tinos and Mykonos islands, Laurium and Northern Euboea.
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PAYOT, Betchaida D., Shoji ARAI, and Rodolfo A. TAMAYO Jr. "Abyssal harzburgite veined by silica-oversaturated melt in the Sibuyan Ultramafics, Romblon, Central Philippines." Journal of Mineralogical and Petrological Sciences 106, no. 3 (2011): 175–80. http://dx.doi.org/10.2465/jmps.101020c.
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Rona, P. A., L. Widenfalk, and K. Boström. "Serpentinized ultramafics and hydrothermal activity at the Mid-Atlantic Ridge crest near 15°N." Journal of Geophysical Research 92, B2 (1987): 1417. http://dx.doi.org/10.1029/jb092ib02p01417.
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