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Phase equilibrium modeling of zircon stability in mantle peridotite:Implication for crust-mantle interaction

Science China Earth Sciences 2022年第2期65卷 282-298页

作者： Hua XIANG Jianping ZHENG Yibing LI Zeming ZHANG Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources Institute of GeologyChinese Academy of Geological SciencesBeijing 100037China School of Earth Sciences State Key Laboratory of Geological Processes and Mineral ResourcesChina University of GeosciencesWuhan 430074China

Zircon is a common accessory mineral in various rocks,especially in the crustal *** is the best mineral for U-Pb ***,trace elements and isotopes of the mineral can also provide much information concerning the formation and evolution of *** are a growing number of reports of zircon existing in mantle ***,it is generally considered that zircon is unlikely crystallized in ultrabasic rocks due to SiO_(2)-*** this paper,the SiO_(2) activity and zircon/baddeleyite transition curve at different conditions were calculated through thermodynamic phase equilibrium modeling,to reveal the main factors affecting the SiO_(2) activity and the stability of zircon/baddeleyite in ultrabasic and basic rocks,especially in mantle *** results provide a thermodynamic basis for interpreting the genesis and significance of zircon in mantle *** is,the SiO_(2) activity is mainly controlled by stable mineral assemblages and temperature-pressure *** orthopyroxene+olivine assemblage in peridotite as an effective buffer restricts the SiO_(2) activity in a relatively high range with a small *** upper temperature limit of zircon can reach more than 1500℃ with this mineral *** the low-temperature serpentinization of peridotite,the replacement of olivine and pyroxene by serpentine can result in a significant decrease of SiO_(2) activity,and baddeleyite can be stabilized atperidotite is strongly metasomatized by the SiO_(2)-bearing fluid,the addition of SiO_(2) can increase its activity and make zircon stable at low *** SiO_(2) activity in ultrabasic-basic rocks is not only positively correlated with the SiO_(2) content but also negatively correlated with the Ca and Na contents of *** is because Ca and Na preferentially combine with Si and Al to form Si-rich minerals,such as clinopyroxene and *** process will consume excessive SiO_(2),decreasing

关键词： Zircon Baddeleyite Phase equilibrium modeling mantle peridotite Ultrabasic rock

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In-situ Moissanite in Dunite: Deep mantle Origin of mantle peridotite in Luobusa Ophiolite, Tibet

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Acta Geologica Sinica(English Edition) 2014年第2期88卷 517-529页

作者： LIANG Fenghua XU Zhiqin ZHAO Jianan State Key Laboratory of Continental Tectonics and Dynamics Institute of GeologyChinese Academy of Geological Sciences School of Earth Sciences and Resources China University of Geosciences

We report the discovery of an in-situ natural moissanite as an inclusion in the Cr-spinel from the dunite envelope of a chromitite deposit in Luobusa ophiolite,*** moissanite occurs as a twin crystal interpenetrated by two quadrilateral signal crystals with sizes of 17 pm × 10 μm and 20 μm × 7 μm,*** moissanite is green with parallel *** absorption peaks in its Raman spectra are at 967-971 cm-1,787-788 cm-1,and 766 *** absorption peaks in the infrared spectra are at 696 cm-1,767 cm-1,1450 cm-1,and 1551 cm-1,which are distinctly different from the peaks for synthetic silicon *** have been documented to form in ultra-high pressure,high temperature,and extremely low fO2 environments and their 13C-depleted compositions indicate a lower mantle *** with previous studies about other ultra-high pressure and highly reduced minerals in Luobusa ophiolite,the in-situ natural moissanite we found indicates a deep mantle origin of some materials in the mantle sequence of Luobusa ***,we proposed a transformation model to explain the transfer process of UHP materials from the deep mantle to ophiolite sequence and then to the supra-subduction zone *** between the crown of the mantle plume and mid-ocean ridge are suggested to be the dominant mechanism.

关键词： moissanite deep mantle origin mantle peridotite Luobusa ophiolite Tibet

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Experimental Study of Partial Melting of mantle peridotite -A Discussion about the Genesis of Sih'ca-rich Fluids (Melts)

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Acta Geologica Sinica(English Edition) 1999年第4期73卷 395-403页

作者： LI Jianping Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640, Chinaand Kornprobst JACQUES Departement des Sciences de la Terre, Universite Blaise Pascal, 610038 Clermont-Ferrand, France Chinese Acad Sci Guangzhou Inst Geochem Guangzhou 510640 Peoples R China Univ Blaise Pascal Dept Sci Terre F-610038 Clermont Ferrand France

Experiments on partial melting of mantle lherzolite have been realized at 0.6 and 1.0 GPa and the chemical compositional variations of melts during different melting stages have been first discussed. The results show that the trends of variations in SiO2, CaO, Al2O3, Na2O and TiO2 are different at different melting stages. The melts produced at lower pressure are richer in SiO2 than those at higher pressure. The mantle-derived silica-rich fluids (silicate melts) are polygenetic, but the basic and intermediate-acid silicate melts in mantle peridotite xenoliths from the same host rocks, which have equivalent contents of volatile and alkali components and different contents of other components, should result from in-situ (low-degree) partial melting of mantle peridotite under different conditions (e.g. at different depths, with introduction of C-O-H fluids or in the presence of metasomatic minerals). The intermediate-acid melts may be the result of partial melting (at lower pressure) Opx + Sp + K-Na-rich fluid ±(Am-phi) ± (Phlog) = OI + melt. But the intermediate-acid magmas cannot be produced from the partial melting of normal mantle peridotite unless the crustal materials are introduced to some extent.

关键词： mantle peridotite in-situ partial melting compositional variation of melt genesis of silica-rich fluid (stlicate melt)

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Hydro-uvarovite from mantle peridotites of Naga Hills Ophiolite: A Mineral Tracer for Neo-Tethyan mantle Wedge Metasomatism

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Acta Geologica Sinica(English Edition) 2024年第4期98卷 867-877页

作者： Anisha VERENCAR Abhishek SAHA Nilanjana SORCAR Sohini GANGULY Pankaj KUMAR Atul Kumar SINGH CSIR-National Institute of Oceanography Dona PaulaGoa 403004India School of Earth Ocean and Atmospheric SciencesGoa UniversityTaleigao PlateauGoa 403206India National Centre for Earth Science Studies ThiruvananthapuramKeralaIndia Inter University Accelerator Centre(IUAC) New Delhi 110067India North-Eastern Hill University ShillongMeghalaya 793022India

Hydrous Cr-bearing uvarovite garnets are rare in natural occurrences and belong to the ugrandite series and exist in binary solid solutions with grossular and andradite garnets. Here, we report the occurrence of hydrous uvarovite garnet having Cr_(2)O_(3) upto 19.66 wt% and CaO of 32.12–35.14 wt% in the serpentinized mantle peridotites of Naga Hills Ophiolite(NHO), India. They occur in association with low-Cr diopsides. They are enriched in LILE(Ba, Sr), LREEs, with fractionating LREE-MREE [avg.(La/Sm)_(N) = 2.16] with flat MREE/HREE patterns [avg.(Sm/Yb)_(N) = 0.95]. Raman spectra indicate the presence of hydroxyl(OH^(–)) peaks from 3500 to 3700 cm^(-1). Relative abundances in fluid mobile elements and their close association with clinopyroxenes are suggestive of the formation of uvarovite garnets through low temperature metasomatic alteration of low-Cr diopsides by hydrothermal slab fluids. The high LREE concentration and absence of Eu anomaly in the garnet further attest to alkaline nature of the transporting slab dehydrated fluid rather the involvement of low-p H solution. The chemical characteristics of the hydroxyl bearing uvarovite hosted by the mantle peridotite of NHO deviate from the classical features of uvarovite garnet, and their origin is attributed to the fluid-induced metasomatism of the sub arc mantle wedge in a suprasubduction zone regime.

关键词： uvarovite hydroxyl metasomatic alteration low-Cr diopsides serpentinization mantle peridotite

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Melt migration and melt-rock reaction in the Alpine-Apennine peridotites:Insights on mantle dynamics in extending lithosphere

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Geoscience Frontiers 2020年第1期11卷 151-166页

作者： Elisabetta Rampone Giulio Borghini Valentin Basch DISTAV University of GenovaCorso Europa 26I-16132 GenovaItaly Dipartimento di Scienze della Terra University of Milanovia Botticelli 2320133 MilanoItaly

The compositional variability of the lithospheric mantle at extensional settings is largely caused by the reactive percolation of uprising melts in the thermal boundary layer and in lithospheric *** Alpine-Apennine(A-A)ophiolites are predominantly constituted by mantle peridotites and are widely thought to represent analogs of the oceanic lithosphere formed at ocean/continent transition and slow-to ultraslow-spreading *** and geochemical studies on the A-A mantle peridotites have revealed that they preserve significant compositional and isotopic heterogeneity at variable scale,reflecting a long-lived multi-stage melt migration,intrusion and melt-rock interaction history,occurred at different lithospheric depths during progressive *** A-A mantle peridotites thus constitute a unique window on mantle dynamics and lithosphere-asthenosphere interactions in very slow spreading *** this work,we review field,microstructural and chemical-isotopic evidence on the major stages of melt percolation and melt-rock interaction recorded by the A-A peridotites and discuss their consequences in creating chemical-isotopic heterogeneities at variable scales and enhancing weakening and deformation of the extending *** will be on three most important stages:(i)old(pre-Jurassic)pyroxenite emplacement,and the significant isotopic modification induced in the host mantle by pyroxenite-derived melts,(ii)melt-peridotite interactions during Jurassic mantle exhumation,*** open-system reactive porous flow at spinel facies depths causing bulk depletion(origin of reactive harzburgites and dunites),and the shallower melt impregnation which originated plagioclase-rich peridotites and an overall mantle *** infer that migrating melts largely originated as shallow,variably depleted,melt fractions,and acquired Si-rich composition by reactive dissolution of mantle pyroxenes during upward *** melt-rock reaction processes

关键词： mantle peridotite Pyroxenite Melt migration Melt impregnation Melt-rock reaction Alpine-Apennine ophiolites

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Lithium elemental and isotopic disequilibrium in minerals from peridotite xenoliths from Shangzhi, NE China： products of recent melt/fluid-peridotite interaction

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Acta Geochimica 2018年第5期37卷 769-789页

作者： Shenghua Zhou Songyue Yu Ting Zhou Jiangbo Lan Jian Kang Liemeng Chen Junhao Hu State Key Laboratory of Ore Deposit Geochemistry Institute of Geochemistry Chinese Academy of SciencesGuiyang 550081 PR China University of Chinese Academy of Sciences Beijing 100049PR China

Lithium elemental and isotopic disequilibrium has frequently been observed in the continental and oceanic mantle xenoliths, but its origin remains controversial. Here,we present a combined elemental and Li isotopic study on variably metasomatised peridotite xenoliths entrained in the Cenozoic basalts from Shangzhi in Northeast (NE) China that provides insight into this issue. Li concentration (0.3–2.7 ppm) and δ7 Li (mostly 2‰–6‰) in olivine from the Shangzhi peridotites are similar to the normal mantle values and show roughly negative correlations with the indices of melt extraction(such as modal olivine and whole rock MgO). These features are consistent with variable degrees of partial melting. In contrast, clinopyroxene from the Shangzhi xenoliths shows significant Li enrichment (0.9–6.1 ppm) and anomalously light δ7 Li (-13.8‰ to7.7‰) relative to normal mantle values. Such features can be explained by Li diffusion from silicate melts or Li-rich fluids occurring over a very short time(several minutes to several hours). Moreover, the light Li isotopic compositions preserved in some bulk samples also indicate that these percolated melts/fluids have not had enough time to isotopically equilibrate with the bulk peridotite. We thus emphasize that Li isotopic fractionation in the Shangzhi mantle xenoliths is mainly related to Li diffusion from silicate melts or Li-rich fluids that took place shortly before or coincident with their entrainment into the host magmas.

关键词： mantle peridotite Li isotope mantle metasomatism Northeastern China

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Mineral Chemistry and Geochemistry of peridotites from the Zedang and Luobusa Ophiolites, Tibet: Implications for the Evolution of the Neo-Tethys

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Journal of Earth Science 2015年第6期26卷 893-910页

作者： Qiang Li Bin Xia Jianfeng Li Lianze Xia Qiangtai Huang Zhongyu Xia School of Marine Sciences Sun Yat-Sen University Qingdao Institute of Marine Geology Guang zhou Institute of Geochemistry Chinese Academy of Sciences Department of Earth Sciences Sun Yat-Sen University

We present a new dataset on platinum group elements（PGEs）, whole-rock major and trace elements, and mineral chemistry for the peridotites from the Zedang and Luobusa ophiolite suites, Tibet, in an attempt to better constrain the petrogenesis of the Zedang and Luobusa ophiolites and the tectonic evolution of the Neo-Tethys. Plots of chondrite-normalized PGE, PGE vs. Mg#, and PGE vs. Al_2O_3 suggest that the lherzolite and harzburgite from Zedang and Luobusa have similar PGE characteristics. The Zedang and Luobusa peridotites display U-shaped REE patterns and are enriched in some incompatible elements, indicative of melt-rock interaction. The PGE characteristics may be attributed to partial melting and heterogeneous melt-rock interaction. Mineral chemistry and whole rock major and trace elements data suggest that lherzolite and harzburgite from Zedang and Luobusa have similar geochemical properties. On the spinel Mg# vs. Cr# plot, the composition of the Zedang and Luobusa peridotites is consistent with both abyssal and subduction-zone peridotites. This study indicates that the Zedang and Luobusa peridotites have a similar origin and evolution path： they could have originated from a normal mid-ocean ridge environment and got refertilization in a supra-subduction zone setting.

关键词： Zedang-Luobusa ophiolite mantle peridotite PGE melt-rock interaction Yarlung Zangbo suture zone

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Reconsideration of Neo-Tethys Evolution Constrained from the Nature of the Dazhuqu Ophiolitic mantle, Southern Tibet

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Acta Geologica Sinica(English Edition) 2020年第S1期94卷 36-36页

作者： LIU Tong WU Fuyuan LIU Chuanzhou ZHANG Chang JI Wenbin XU Yang State Key Laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China

The nature(i.e., sub-oceanic, sub-arc or subcontinental) of ophiolitic mantle peridotites from the eastern Neo-Tethyan domain in southern Tibet has been hotly debated. This uncertainty limits our understanding of the history and evolution of the eastern Neo-Tethys Ocean. Here we present petrological, geochemical and Re-Os isotopic data for the mantle peridotites from the Dazhuqu ophiolite in the central segment of the Yarlung Zangbo suture zone, southern Tibet. Samples collected include both spinel lherzolites and spinel harzburgites. The lherzolites have spinel Cr~# [Cr/(Cr + Al), ~ 0.3–0.4] comparable to those of typical abyssal peridotites. In contrast, the harzburgites have spinel Cr~#(~0.3–0.7) overlapping with the ranges of both abyssal and fore-arc peridotites(Day et al., 2017;Parkinson and Pearce, 1998);two samples have spinel Cr~# higher than 0.6, which is probably ascribed to intense melt-rock interactions. Clinopyroxene trace element modeling indicates that the Dazhuqu mantle peridotites have experienced 0–6% garnetfacies melting followed by 10% –18% melting in the spinel stability field. This is similar to the degree of garnet-facies melting inferred for many abyssal peridotites(Hellebrand et al., 2002) and implies deep initial melting(> 85 km), which distinguishes the Dazhuqu mantle peridotites from fore-arc peridotites(commonly peridotites have unradiogenic 187 Os/188 Os of 0.11836–0.12922, which are commonly lower than the recommended value of primitive upper mantle(PUM)(Meisel et al., 2001). All but one samples yield relatively younger Re depletion ages(TRD = 0.06–0.81 Ga) with respect to the only one sample having an older TRD age of 1.66 Ga. Re-Os isotopes and highly siderophile element(HSE) compositions of the Dazhuqu peridotites are similar to those of abyssal peridotites(Day et al., 2017) and the Oman southern massifs(Hangh?j et al., 2010) but are distinct from noncratonic sub-continental lithospheric mantle(SCLM)

关键词： Neo-Tethys Ocean sub-oceanic mantle Re-Os isotope mantle peridotite Dazhuqu ophiolite Yarlung Zangbo suture zone

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The origin of spongy texture in minerals of mantle xenoliths from the Western Qinling,central China

The origin of spongy texture in minerals of mantle xenoliths...

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中国科学院地质与地球物理研究所第11届（2011年度）学术年会

作者： Patrick Asamoah Sakyi Department of Earth Science University of Ghana.P.O.Box LG 58Legon-AccraGhana

Spongy textures are observed in mantle peri-dotite xenoliths hosted in Cenozoic kamafugites from the Western Qinling,central *** textures are mainly developed in clinopyroxenes and spinels,and occur as spongy rims consisting of low-Na clinopyroxene,ilmenite, and bubbles,enclosing nonspongy *** ilmenites and bubbles exhibit shapes and sizes that vary with the width of the spongy *** spongy-textured minerals preserve primary shapes and well-defined grain boundaries and do not show apparent interaction with contact minerals or observed melts except the subsequent melts forming melt *** xenocrysts display reactive zoning textures with host magmas rather than spongy ***-tionally, the spongy rims are enriched in Ca,Ti,and most trace elements,have high Cr#,and are depleted in Na,Al, Fe,A1,and A1/A1 compared with the *** observations suggest that melts/host magmas did not play any significant role in the formation of the spongy textures. We therefore propose that spongy-textured clinopyroxenes and spinels in Western Qinling peridotite xenoliths developed from a decompression-induced partial melting event prior to formation of melt pockets and xenolith entrainment in host magmas.

关键词： Decompression mantle peridotite Partial melting Spongy texture Western Qinling

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Compositionally stratified lithosphere and carbonatite metasomatism recorded in mantle xenoliths from the Western Qinling(Central China)

Compositionally stratified lithosphere and carbonatite metas...

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中国科学院地质与地球物理研究所第十届(2010年度)学术年会

作者： Asamoah Sakyi Department of Geology University of Ghana

In Central China,long-distance effects from collision between the North China and Yangtze cratons,uplift of the Tibetan Plateau and subduction of the Pacific Ocean are believed to converge in the Western Ojnling. mantle xenoliths from Baiguan and Haoti kamafugites in the Western Ojnling were investigated to understand the lithospheric structure and mantle metasomatism beneath the orogenic *** Western Ojnling lithosphere with depths of at least 120 km is geothermally hot and compositionally stratified, companied by a step-wise decrease in fertility with *** shallower portion of the lithospheric mantle is represented by type 2 xenoliths which lack alteration and deformation,and have fertile characteristics in *** dominant rock type in the mantle section is the type 1 peridotites,which have had undergone relatively higher melt extraction and subsequent metasomatism. In-situ trace element data for minerals in the Baiguan and Haoti xenoliths are presented in this study. Baiguan clinopyroxenes have high LREE and show Ba,Th,U,Pb,Sr enrichment and negative Hf and Y anomalies,but the Haoti clinopyroxenes have large variations in trace elements and complicated distributions in LILE,and show negative Ti,Zr and Hf *** from both xenolith types have Ti/Eu and(La/Yb) ratios in large ranges of 902-15,813 and 0-20,*** petrological and geochemical characteristics suggest that the Western Ojnling peridotites had been subjected to silicate and subsequent carbonatite metasomatism,and that carbonatite metasomatism was predominant in Baiguan but lesser in *** with the Western Ojnling carbonatites and world-wide carbonatites indicate that carbonatite melts involved in the metasomatism originated from deep mantle and most likely related to carbonatite magma,with contributions from subducted oceanic *** type 2 peridotites,comprising clinopyroxene megacrysts and clinopyroxenite display similar trace element abundanc

关键词： Carbonatite metasomatism mantle peridotite Stratified lithospheric mantle Western Qinling

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