Fahui Xiong - Academia.edu (original) (raw)

Papers by Fahui Xiong

Research paper thumbnail of ZANGBO縫合は,マントル橄欖岩の白金族元素の特徴をタザロテンない。【JST・京大機械翻訳】

Research paper thumbnail of Petrology and geochronology of MOR gabbro in the Purang ophiolite of western Tibet,China

Yanshi Xuebao, 2011

The Purang ophiolite in the western part of the Yarlung Zangbo suture zone,is composed of mantle ... more The Purang ophiolite in the western part of the Yarlung Zangbo suture zone,is composed of mantle peridotite,gabbro and basalt.A gabbro massif,about 1km2 in area,occurs south of Lhanag-tso.The gabbro is fine-to medium-grained with a massive texture,and is composed mainly of subhedral tabular to prismatic plagioclase and anhedral to subhedral granular pyroxene.The gabbro has a MOR-type composition with relatively high TiO2(1.00%～1.77%) and low K2O(0.08%～0.21%) and P2O5(0.1%).It is characterized by having a nearly flat chondrite-normalized REE pattern with only slightly depleted LREE,as indicated by(La/Ce)N=0.73～0.80,(La/Sm)N=0.44～0.58 and(La/Yb)N=0.53～0.65.An N-MORB-normalized spider diagram shows enrichment in LILE(e.g.,Rb) and slight depletion in HFSE.U-Pb dating of zircons from gabbro of the Purang ophiolite yields an age of 130±3Ma.This age is similar to that of the nearby Xiugugabu and Dongbo ophiolite,and is taken as the crystallization age of the Purang ophiolite.

Research paper thumbnail of Petrogenesis of mafic rocks from the Xigaze ophiolite, Southern Tibet: Insights into forearc extension induced by Neotethyan rollback

Research paper thumbnail of Feature of Zedong podiform chromitite,eastern Yarlung-Zangbo suture zone in Tibet

Research paper thumbnail of Ophiolites and Earth's mantle ophiolites, podiform chromitites and deep mantle recycling

Research paper thumbnail of Microchemistry and magnesium isotope composition of the Purang ophiolitic chromitites (SW Tibet): New genetic inferences

American Mineralogist

New petrographic and microanalytical studies of mineral inclusions in the Purang ophiolitic chrom... more New petrographic and microanalytical studies of mineral inclusions in the Purang ophiolitic chromitites (SW Tibet) are used to scrutinize the evolution of the associated Cretaceous sub-oceanic lithospheric mantle section. Silicate inclusions in the chromite grains include composite and single-phase orthopyroxene, clinopyroxene, amphibole, and uvarovite. Most inclusions are sub-rounded or globular, whereas a few inclusions exhibit cubic/octahedral crystal morphologies. The latter are randomly distributed in the large chromite grains, though discrete aggregates are consistently confined to the grain centers. Abundant micrometer-scale, clinopyroxene inclusions are topotaxially aligned along crystallographic planes. Less-abundant sulfide, wüstite, apatite, and uvarovite inclusions are observed in some samples. The trace element geochemistry of the Purang chromitite evoke parental MORB- and boninite-like melts, consistent with the supra-subduction zone setting. The δ26Mg values of the hi...

Research paper thumbnail of Tectonized Neotethyan lithosphere in southeastern Tibet: Results of the Luobusa ophiolite drilling

Research paper thumbnail of Genesis and high-pressure evolution of the Köyceğiz ophiolite (SW Turkey): Mineralogical and geochemical characteristics of podiform chromitites

Research paper thumbnail of Wenjiite, Ti10(Si,P,☐)7, and kangjinlaite, Ti11(Si,P)10, new minerals in the ternary Ti-P-Si system from the Luobusa ophiolite, Tibet, China

American Mineralogist, 2022

The new minerals wenjiite, Ti10(Si,P,☐)7 (IMA2019-107c) and kangjinlaite, Ti11(Si,P)10 (IMA2019-1... more The new minerals wenjiite, Ti10(Si,P,☐)7 (IMA2019-107c) and kangjinlaite, Ti11(Si,P)10 (IMA2019-112b) occur with badengzhuite, zhiqinite, and a K-bearing dmisteinbergite-like mineral in a spheroid 20 μm across enclosed in corundum from the Cr-11 podiform chromitite orebody near the Kangjinla, Luobusa ophiolite, Tibet, China. In addition, wenjiite occurs with deltalumite, jingsuiite, osbornitekhambaraevite, and the K-bearing dmisteinbergite-like mineral in a lamellar intergrowth 100 μm long, also enclosed in corundum from the same locality. The new minerals were characterized by energy-dispersive spectroscopy and three-dimensional electron diffraction, which enabled us to obtain an ab initio structure solution and dynamical refinement from grains a few micrometers across hosted in a FIB lamella. Four analyses of wenjiite from the spheroid gave in wt% Si 21.67, P 6.24, Ti 66.39, V 1.37, Cr 2.20, Mn 0.97, and Fe 1.17 (normalized to 100), which corresponds to (Ti0.93Cr0.03Mn0.01Fe0.01V0...

Research paper thumbnail of Multi-stage Process of the Bulqiza Chromitites, Eastern Ophiolitic Belt, Albania

Acta Geologica Sinica - English Edition, 2016

Research paper thumbnail of Petrology of Cr-rich Podiform Chromitites of Bulqiza, Eastern Ophiolitic Belt, Albania

Acta Geologica Sinica - English Edition, 2015

Research paper thumbnail of Petrological and Os isotopic constraints on the origin of the Dongbo peridotite massif, Yarlung Zangbo Suture Zone, Western Tibet

Journal of Asian Earth Sciences, 2015

The Dongbo peridotite massif in the western part of the Yarlung Zangbo Suture Zone (YZSZ) in sout... more The Dongbo peridotite massif in the western part of the Yarlung Zangbo Suture Zone (YZSZ) in southern Tibet represents a mantle thrust sheet of more than 400 km 2 , tectonically overlying a Cretaceous mélange. Spinel-harzburgite with a porphyroclastic texture is the main rock type, accompanied by subordinate dunite. Olivine (Fo 90.3-91.3), orthopyroxene (En 87-90), clinopyroxene (En 49-51 Wo 46-51 Fs 0-4) and spinel [Mg# = 100Mg/(Mg + Fe)] = 41.1-73.1; Cr# = (100Cr/(Cr + Al) = 23.6-87.3] are the major minerals. The peridotites are characterized by ''spoon-shaped'', chondrite-normalized REE patterns with (La/ Yb) CN = 0.09-0.40, and (Gd/Yb) CN = 0.23-0.95. The patterns show relative uniform depletion from Lu to Nd, followed by slight enrichment from Nd to La. These rocks represent residues of mantle rocks after variable degrees of basaltic magma extraction beneath a seafloor spreading environment, followed by modification by percolating, suprasubduction-related melts. The Dongbo peridotites have variable, unradiogenic Os isotopic compositions with 187 Os/ 188 Os = 0.1235-0.1282 and rhenium-depletion ages (T RD) = 0.22-0.96 Ga, implying heterogeneity of Os isotopes in the mantle beneath Neotethys. A corollary to this interpretation is that the convecting upper mantle is heterogeneous in Os isotopes.

Research paper thumbnail of Geochemical constraints on the multistage evolution of the Yilashan ophiolite, central Tibet

Research paper thumbnail of Genesis of Pyroxenite Veins in the Zedang Ophiolite, the Southern Tibetan Plateau

Acta Geologica Sinica - English Edition

Research paper thumbnail of Origin and significance of diamonds and other exotic minerals in the Dingqing ophiolite peridotites, eastern Bangong-Nujiang suture zone, Tibet

Lithosphere, 2017

We have recovered unusual mineral assemblages of diamond, moissanite, zircon, quartz, corundum, r... more We have recovered unusual mineral assemblages of diamond, moissanite, zircon, quartz, corundum, rutile, titanite, almandine garnet, kyanite, and andalusite from the peridotites of the Late Triassic Dingqing ophiolite along the Bangong-Nujiang suture zone in south-central Tibet. Diamond grains are 100-300 μm, pale yellow and reddish-orange to colorless, commonly anhedral in habit, and range in morphology from elongated to octahedral and subhedral crystals. They display a characteristic shift in the Raman spectra between 1325 cm-1 and 1333 cm-1 , mostly at 1331.51 cm −1 or 1326.96 cm −1. Chromian spinels in the Dingqing harzburgites and dunites are high-Cr varieties with Cr# = 40.1-49.1 and Cr# = 65.3-69.6, respectively. Recovered diamonds, ultrahigh-pressure, and highly reduced minerals appear to have crystallized and then been encapsulated in chromian spinel grains over a wide range of depth in the diamond stability field near the mantle transition zone. These chromian spinels and their host peridotites were then brought up to shallow mantle levels by the convecting asthenosphere, and were subsequently trapped in a mantle wedge of an intraoceanic subduction zone. The peridotites underwent further partial melting processes and reactions with island arc tholeiitic and boninitic melts, significantly modifying their whole-rock and mineral compositions. The preexisting chromian spinel grains with the inclusions of diamonds and other exotic minerals coalesced to form podiform chromitites during this stage in a suprasubduction zone setting.

Research paper thumbnail of Petrology of Cr-rich Ophiolitic Chromitites of Bulqiza, Eastern Ophiolitic Belt, Albania

Acta Geologica Sinica - English Edition, 2015

Research paper thumbnail of Petrology and geochemistry of high Cr# podiform chromitites of Bulqiza, Eastern Mirdita Ophiolite (EMO), Albania

Ore Geology Reviews, 2015

ABSTRACT The ultramafic massif of Bulqiza, which belongs to the eastern ophiolitic belt of Albani... more ABSTRACT The ultramafic massif of Bulqiza, which belongs to the eastern ophiolitic belt of Albania, is a major source of metallurgical chromitite ore. The massif consists of a thick (> 4 km) sequence, composed from the base upward of tectonized harzburgite with minor dunite, a transitional zone of dunite, and a magmatic sequence of wehrlite, pyroxenite, troctolite and gabbro. Only sparse, refractory chromitites occur within the basal clinopyroxene-bearing harzburgites, whereas the upper and middle parts of the peridotite sequence contain abundant metallurgical chromitites. The transition zone dunites contain a few thin layers of metallurgical chromitite and sparse bodies are also present in the cumulate section. The Bulqiza Ophiolite shows major changes in thickness, like the 41–50 wt.% MgO composition similar with forearc peridotite as a result of its complex evolution in a suprasubduction zone (SSZ) environment. The peridotites show abundant evidence of mantle melt extraction at various scales as the orthopyroxene composition change from core to rim, and mineral compositions suggest formation in a forearc, as Fo values of olivine are in 91.1–93.0 harzburgite and 91.5–91.9 in dunite and 94.6–95.9 in massive chromitite. The composition of the melts passing through the peridotites changed gradually from tholeiite to boninite due to melt–rock reaction, leading to more High Cr# chromitites in the upper part of the body. Most of the massive and disseminated chromitites have high Cr# numbers (70–80), although there are systematic changes in olivine and magnesiochromite compositions from harzburgites, to dunite envelopes to massive chromitites, reflecting melt–rock reaction. Compositional zoning of orthopyroxene porphyroblasts in the harzburgite, incongruent melting of orthopyroxene and the presence of small, interstitial grains of spinel, olivine and pyroxene likewise attest to modification by migrating melts. All of the available evidence suggests that the Bulqiza Ophiolite formed in a suprasubduction zone mantle wedge.

Research paper thumbnail of Mineralogical and isotopic peculiarities of high-Cr chromitites: Implications for a mantle convection genesis of the Bulqiza ophiolite

Lithos, 2021

Submicroscopic to micro-diamonds, silicates, wustite, platinum group minerals (PGM), sulfides and... more Submicroscopic to micro-diamonds, silicates, wustite, platinum group minerals (PGM), sulfides and ultra-high pressure (UHP) mineral inclusions have been recovered from podiform and banded chromitites of the Bulqiza ophiolite in Albania. The alignment of acicular silicate inclusions with crystallographic planes of magnesiochromite suggests an exsolution origin. Positive and negative-crystal faces of cubic silicate inclusions are consistent withs a high-temperature paragenesis. Micro-inclusions and nanoparticles ( Os bisulfides (laurite; RuS2), Os Ir, and Os-Ir-Ru alloys, tolovike, irarsite, Ir Ni sulfides, and millerite (NiS) are also common in the Bulqiza chromitites. Dispersed spherical, nano-inclusions of Ir Pt and Os Ir may reflect formation of the Ir Pt and Os Ir particles by sulfide liquid immiscibility. The high Cr# of the chromitites, their evolved whole-rock PGE abundances, and IPGE/PPGE ratios (≥ 10) suggest extensive partial melting, likely in a supra-subduction zone (SSZ)...

Research paper thumbnail of Petrologocal and Re-Os Isotopic Constraints on the Origin and Tectonic Setting of the Cuobuzha Peridotite, Yarlung Zangbo Suture Zone, Western Tibet, China

Research paper thumbnail of The Characteristics and Significance of Peng Co Peridotites in the Middle Segment of Bangong Co‐Nujiang Suture in Tibet

Acta Geologica Sinica-english Edition, 2020

The Peng Co ophiolite is located to the west of Peng lake in the area of lakes in north Tibet, wh... more The Peng Co ophiolite is located to the west of Peng lake in the area of lakes in north Tibet, which belongs to the Baila-Yilashan sub-belt of the the middle Bangong Co-Nujiang ophiolitic belt. The Peng Co ophiolite is mainly composed of mantle peridotites, cumulates, diabase dikes. About 70 percent peridotites are harzburgites and 30 percent are lherzolites. Mineral chemistry of the Peng Co lherzolitesare characterized by low Fo contents (88.85–90.33) of olivine and high Al2O3 content (4.26%–7.25%) in pyroxenes. Compared to the primitive mantle, the Peng Co peridotites have relatively higher MgO contents, lower CaO, Al2O3 and TiO2 contents. The total rare-earth element (REE) contents of the lherzolites are 1.11–1.53 ppm, which are lower than those of the primitive mantle. The chondritenormalized REE patterns of the Peng Co peridotites display slight loss in LREE. In the primitive mantle-normalized spider diagram, the Peng Co peridotites exhibit negative Rb and Zr anomalies and inte...

Research paper thumbnail of ZANGBO縫合は,マントル橄欖岩の白金族元素の特徴をタザロテンない。【JST・京大機械翻訳】

Research paper thumbnail of Petrology and geochronology of MOR gabbro in the Purang ophiolite of western Tibet,China

Yanshi Xuebao, 2011

The Purang ophiolite in the western part of the Yarlung Zangbo suture zone,is composed of mantle ... more The Purang ophiolite in the western part of the Yarlung Zangbo suture zone,is composed of mantle peridotite,gabbro and basalt.A gabbro massif,about 1km2 in area,occurs south of Lhanag-tso.The gabbro is fine-to medium-grained with a massive texture,and is composed mainly of subhedral tabular to prismatic plagioclase and anhedral to subhedral granular pyroxene.The gabbro has a MOR-type composition with relatively high TiO2(1.00%～1.77%) and low K2O(0.08%～0.21%) and P2O5(0.1%).It is characterized by having a nearly flat chondrite-normalized REE pattern with only slightly depleted LREE,as indicated by(La/Ce)N=0.73～0.80,(La/Sm)N=0.44～0.58 and(La/Yb)N=0.53～0.65.An N-MORB-normalized spider diagram shows enrichment in LILE(e.g.,Rb) and slight depletion in HFSE.U-Pb dating of zircons from gabbro of the Purang ophiolite yields an age of 130±3Ma.This age is similar to that of the nearby Xiugugabu and Dongbo ophiolite,and is taken as the crystallization age of the Purang ophiolite.

Research paper thumbnail of Petrogenesis of mafic rocks from the Xigaze ophiolite, Southern Tibet: Insights into forearc extension induced by Neotethyan rollback

Research paper thumbnail of Feature of Zedong podiform chromitite,eastern Yarlung-Zangbo suture zone in Tibet

Research paper thumbnail of Ophiolites and Earth's mantle ophiolites, podiform chromitites and deep mantle recycling

Research paper thumbnail of Microchemistry and magnesium isotope composition of the Purang ophiolitic chromitites (SW Tibet): New genetic inferences

American Mineralogist

New petrographic and microanalytical studies of mineral inclusions in the Purang ophiolitic chrom... more New petrographic and microanalytical studies of mineral inclusions in the Purang ophiolitic chromitites (SW Tibet) are used to scrutinize the evolution of the associated Cretaceous sub-oceanic lithospheric mantle section. Silicate inclusions in the chromite grains include composite and single-phase orthopyroxene, clinopyroxene, amphibole, and uvarovite. Most inclusions are sub-rounded or globular, whereas a few inclusions exhibit cubic/octahedral crystal morphologies. The latter are randomly distributed in the large chromite grains, though discrete aggregates are consistently confined to the grain centers. Abundant micrometer-scale, clinopyroxene inclusions are topotaxially aligned along crystallographic planes. Less-abundant sulfide, wüstite, apatite, and uvarovite inclusions are observed in some samples. The trace element geochemistry of the Purang chromitite evoke parental MORB- and boninite-like melts, consistent with the supra-subduction zone setting. The δ26Mg values of the hi...

Research paper thumbnail of Tectonized Neotethyan lithosphere in southeastern Tibet: Results of the Luobusa ophiolite drilling

Research paper thumbnail of Genesis and high-pressure evolution of the Köyceğiz ophiolite (SW Turkey): Mineralogical and geochemical characteristics of podiform chromitites

Research paper thumbnail of Wenjiite, Ti10(Si,P,☐)7, and kangjinlaite, Ti11(Si,P)10, new minerals in the ternary Ti-P-Si system from the Luobusa ophiolite, Tibet, China

American Mineralogist, 2022

The new minerals wenjiite, Ti10(Si,P,☐)7 (IMA2019-107c) and kangjinlaite, Ti11(Si,P)10 (IMA2019-1... more The new minerals wenjiite, Ti10(Si,P,☐)7 (IMA2019-107c) and kangjinlaite, Ti11(Si,P)10 (IMA2019-112b) occur with badengzhuite, zhiqinite, and a K-bearing dmisteinbergite-like mineral in a spheroid 20 μm across enclosed in corundum from the Cr-11 podiform chromitite orebody near the Kangjinla, Luobusa ophiolite, Tibet, China. In addition, wenjiite occurs with deltalumite, jingsuiite, osbornitekhambaraevite, and the K-bearing dmisteinbergite-like mineral in a lamellar intergrowth 100 μm long, also enclosed in corundum from the same locality. The new minerals were characterized by energy-dispersive spectroscopy and three-dimensional electron diffraction, which enabled us to obtain an ab initio structure solution and dynamical refinement from grains a few micrometers across hosted in a FIB lamella. Four analyses of wenjiite from the spheroid gave in wt% Si 21.67, P 6.24, Ti 66.39, V 1.37, Cr 2.20, Mn 0.97, and Fe 1.17 (normalized to 100), which corresponds to (Ti0.93Cr0.03Mn0.01Fe0.01V0...

Research paper thumbnail of Multi-stage Process of the Bulqiza Chromitites, Eastern Ophiolitic Belt, Albania

Acta Geologica Sinica - English Edition, 2016

Research paper thumbnail of Petrology of Cr-rich Podiform Chromitites of Bulqiza, Eastern Ophiolitic Belt, Albania

Acta Geologica Sinica - English Edition, 2015

Research paper thumbnail of Petrological and Os isotopic constraints on the origin of the Dongbo peridotite massif, Yarlung Zangbo Suture Zone, Western Tibet

Journal of Asian Earth Sciences, 2015

The Dongbo peridotite massif in the western part of the Yarlung Zangbo Suture Zone (YZSZ) in sout... more The Dongbo peridotite massif in the western part of the Yarlung Zangbo Suture Zone (YZSZ) in southern Tibet represents a mantle thrust sheet of more than 400 km 2 , tectonically overlying a Cretaceous mélange. Spinel-harzburgite with a porphyroclastic texture is the main rock type, accompanied by subordinate dunite. Olivine (Fo 90.3-91.3), orthopyroxene (En 87-90), clinopyroxene (En 49-51 Wo 46-51 Fs 0-4) and spinel [Mg# = 100Mg/(Mg + Fe)] = 41.1-73.1; Cr# = (100Cr/(Cr + Al) = 23.6-87.3] are the major minerals. The peridotites are characterized by ''spoon-shaped'', chondrite-normalized REE patterns with (La/ Yb) CN = 0.09-0.40, and (Gd/Yb) CN = 0.23-0.95. The patterns show relative uniform depletion from Lu to Nd, followed by slight enrichment from Nd to La. These rocks represent residues of mantle rocks after variable degrees of basaltic magma extraction beneath a seafloor spreading environment, followed by modification by percolating, suprasubduction-related melts. The Dongbo peridotites have variable, unradiogenic Os isotopic compositions with 187 Os/ 188 Os = 0.1235-0.1282 and rhenium-depletion ages (T RD) = 0.22-0.96 Ga, implying heterogeneity of Os isotopes in the mantle beneath Neotethys. A corollary to this interpretation is that the convecting upper mantle is heterogeneous in Os isotopes.

Research paper thumbnail of Geochemical constraints on the multistage evolution of the Yilashan ophiolite, central Tibet

Research paper thumbnail of Genesis of Pyroxenite Veins in the Zedang Ophiolite, the Southern Tibetan Plateau

Acta Geologica Sinica - English Edition

Research paper thumbnail of Origin and significance of diamonds and other exotic minerals in the Dingqing ophiolite peridotites, eastern Bangong-Nujiang suture zone, Tibet

Lithosphere, 2017

We have recovered unusual mineral assemblages of diamond, moissanite, zircon, quartz, corundum, r... more We have recovered unusual mineral assemblages of diamond, moissanite, zircon, quartz, corundum, rutile, titanite, almandine garnet, kyanite, and andalusite from the peridotites of the Late Triassic Dingqing ophiolite along the Bangong-Nujiang suture zone in south-central Tibet. Diamond grains are 100-300 μm, pale yellow and reddish-orange to colorless, commonly anhedral in habit, and range in morphology from elongated to octahedral and subhedral crystals. They display a characteristic shift in the Raman spectra between 1325 cm-1 and 1333 cm-1 , mostly at 1331.51 cm −1 or 1326.96 cm −1. Chromian spinels in the Dingqing harzburgites and dunites are high-Cr varieties with Cr# = 40.1-49.1 and Cr# = 65.3-69.6, respectively. Recovered diamonds, ultrahigh-pressure, and highly reduced minerals appear to have crystallized and then been encapsulated in chromian spinel grains over a wide range of depth in the diamond stability field near the mantle transition zone. These chromian spinels and their host peridotites were then brought up to shallow mantle levels by the convecting asthenosphere, and were subsequently trapped in a mantle wedge of an intraoceanic subduction zone. The peridotites underwent further partial melting processes and reactions with island arc tholeiitic and boninitic melts, significantly modifying their whole-rock and mineral compositions. The preexisting chromian spinel grains with the inclusions of diamonds and other exotic minerals coalesced to form podiform chromitites during this stage in a suprasubduction zone setting.

Research paper thumbnail of Petrology of Cr-rich Ophiolitic Chromitites of Bulqiza, Eastern Ophiolitic Belt, Albania

Acta Geologica Sinica - English Edition, 2015

Research paper thumbnail of Petrology and geochemistry of high Cr# podiform chromitites of Bulqiza, Eastern Mirdita Ophiolite (EMO), Albania

Ore Geology Reviews, 2015

ABSTRACT The ultramafic massif of Bulqiza, which belongs to the eastern ophiolitic belt of Albani... more ABSTRACT The ultramafic massif of Bulqiza, which belongs to the eastern ophiolitic belt of Albania, is a major source of metallurgical chromitite ore. The massif consists of a thick (> 4 km) sequence, composed from the base upward of tectonized harzburgite with minor dunite, a transitional zone of dunite, and a magmatic sequence of wehrlite, pyroxenite, troctolite and gabbro. Only sparse, refractory chromitites occur within the basal clinopyroxene-bearing harzburgites, whereas the upper and middle parts of the peridotite sequence contain abundant metallurgical chromitites. The transition zone dunites contain a few thin layers of metallurgical chromitite and sparse bodies are also present in the cumulate section. The Bulqiza Ophiolite shows major changes in thickness, like the 41–50 wt.% MgO composition similar with forearc peridotite as a result of its complex evolution in a suprasubduction zone (SSZ) environment. The peridotites show abundant evidence of mantle melt extraction at various scales as the orthopyroxene composition change from core to rim, and mineral compositions suggest formation in a forearc, as Fo values of olivine are in 91.1–93.0 harzburgite and 91.5–91.9 in dunite and 94.6–95.9 in massive chromitite. The composition of the melts passing through the peridotites changed gradually from tholeiite to boninite due to melt–rock reaction, leading to more High Cr# chromitites in the upper part of the body. Most of the massive and disseminated chromitites have high Cr# numbers (70–80), although there are systematic changes in olivine and magnesiochromite compositions from harzburgites, to dunite envelopes to massive chromitites, reflecting melt–rock reaction. Compositional zoning of orthopyroxene porphyroblasts in the harzburgite, incongruent melting of orthopyroxene and the presence of small, interstitial grains of spinel, olivine and pyroxene likewise attest to modification by migrating melts. All of the available evidence suggests that the Bulqiza Ophiolite formed in a suprasubduction zone mantle wedge.

Research paper thumbnail of Mineralogical and isotopic peculiarities of high-Cr chromitites: Implications for a mantle convection genesis of the Bulqiza ophiolite

Lithos, 2021

Submicroscopic to micro-diamonds, silicates, wustite, platinum group minerals (PGM), sulfides and... more Submicroscopic to micro-diamonds, silicates, wustite, platinum group minerals (PGM), sulfides and ultra-high pressure (UHP) mineral inclusions have been recovered from podiform and banded chromitites of the Bulqiza ophiolite in Albania. The alignment of acicular silicate inclusions with crystallographic planes of magnesiochromite suggests an exsolution origin. Positive and negative-crystal faces of cubic silicate inclusions are consistent withs a high-temperature paragenesis. Micro-inclusions and nanoparticles ( Os bisulfides (laurite; RuS2), Os Ir, and Os-Ir-Ru alloys, tolovike, irarsite, Ir Ni sulfides, and millerite (NiS) are also common in the Bulqiza chromitites. Dispersed spherical, nano-inclusions of Ir Pt and Os Ir may reflect formation of the Ir Pt and Os Ir particles by sulfide liquid immiscibility. The high Cr# of the chromitites, their evolved whole-rock PGE abundances, and IPGE/PPGE ratios (≥ 10) suggest extensive partial melting, likely in a supra-subduction zone (SSZ)...

Research paper thumbnail of Petrologocal and Re-Os Isotopic Constraints on the Origin and Tectonic Setting of the Cuobuzha Peridotite, Yarlung Zangbo Suture Zone, Western Tibet, China

Research paper thumbnail of The Characteristics and Significance of Peng Co Peridotites in the Middle Segment of Bangong Co‐Nujiang Suture in Tibet

Acta Geologica Sinica-english Edition, 2020

The Peng Co ophiolite is located to the west of Peng lake in the area of lakes in north Tibet, wh... more The Peng Co ophiolite is located to the west of Peng lake in the area of lakes in north Tibet, which belongs to the Baila-Yilashan sub-belt of the the middle Bangong Co-Nujiang ophiolitic belt. The Peng Co ophiolite is mainly composed of mantle peridotites, cumulates, diabase dikes. About 70 percent peridotites are harzburgites and 30 percent are lherzolites. Mineral chemistry of the Peng Co lherzolitesare characterized by low Fo contents (88.85–90.33) of olivine and high Al2O3 content (4.26%–7.25%) in pyroxenes. Compared to the primitive mantle, the Peng Co peridotites have relatively higher MgO contents, lower CaO, Al2O3 and TiO2 contents. The total rare-earth element (REE) contents of the lherzolites are 1.11–1.53 ppm, which are lower than those of the primitive mantle. The chondritenormalized REE patterns of the Peng Co peridotites display slight loss in LREE. In the primitive mantle-normalized spider diagram, the Peng Co peridotites exhibit negative Rb and Zr anomalies and inte...