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    Volume 40,2021 Issue 4
      专题研究
    • LIANG Jian-ting, OUYANG Zhi-xia, ZHANG Ying, LI Jian-bo, ZENG Tao, ZHOU Zhi-chao

      2021,40(4):671-686, DOI:

      Abstract:

      The Yiwulüshan metamorphic core complex (MCC) within the northern margin of the North China Craton is a typical representative of large-scale Mesozoic extensional deformation in Northeast Asia continent. Many studies including the fabric characteristics, shear-sense indicators, strain, kinematic vorticity and deformation age have been intensively conducted. However, some problems concerning geochemistry, isotopic characteristics and genesis of the granite within the core of this MCC remain unanswered. The granite of the core within the MCC is composed of biotite monzogranite and granodiorite. Based on previous research, together with the major elements,trace elements and Sr-Nd isotopic data, the paper presents the results of the data and discusses the genesis and geological significance. According to the results obtained, the granite of Yiwulüshan MCC granite is characterized by high silicon and alkali content (SiO2 =61.17%~75.21%, K2O+ Na2O=7.34%~9.03%), thus belonging to metaluminous and peraluminous (A/CNK=0.96~1.08) and can be assigned to genetic type of high-k-calc-alkaline series, suggesting characteristics of I type granites; most granites have weak negative Eu anomaly (δEu=0.71~1.63), enrichment of large ion lithophile elements (e. g., Rb, Ba and Sr) and light rare earth elements, depletion of high field strength elements (e. g., Nb,Ta and Ti) and heavy rare earth elements, high Sr (308×10-6~1 414×10-6, averaging 709×10-6), low Y (3.17×10-6~13.30×10-6, averaging 7.86×10-6) and Yb (0.45×10-6~1.32×10-6, averaging 0.78×10-6), showing the characteristics of adakitic rocks; isotopic data show that the early co-emplacement granites have a wide range of (87Sr/86Sr)i values (0.695 966 ~ 0.707 869) and a lower εNd(t) values (-21.72~-18.32) and were derived from ancient crust and attributed to the partial melting of the thickened lower crust under the background of regional extension; the isotopic data of the later post-emplacement granites range from 0.705 909 to 0.706 774, and have negative εNd(t) values (-20.60~-16.99), which indicates that the post-emplacement granite resulted from the North China Craton extension thinning during the Late Mesozoic.

    • TIAN Yu-lu, LI Ya, MENG Fan-chao, ZHAO Li-ke, WU Zhi-ping, DU Qing

      2021,40(4):687-703, DOI:

      Abstract:

      The petrogenesis of high Ti basalts is a hot issue in the study of the Emeishan large igneous province (ELIP). Due to the spatial differences in geochemical characteristics of high Ti basalts, there is no consensus on the petrogenesis. In this paper, the authors systematically collected geochemical data of high Ti basalts and CA-ID-TIMS U-Pb dating results of zircons in the ELIP, respectively, and subsequently carried out integrated data processing, analysis and simulation. The research results show that the ELIP was formed in 259~258 Ma and the Emeishan high Ti basalts are distributed all over the ELIP. From west to east, the age of rocks shows no remarkable change, and the distribution of rocks changes from thick to thin. The high Ti basalts with little crustal contamination originated from mantle plume with the characteristics of enriched mantle. They experienced a low degree of partial melting with the possibility of the mixture of some lithospheric mantle components, and fractional crystallization was dominated by clinopyroxene. There was an asymmetric mantle plume at the depth of the ELIP. From west to east, the original depth and temperature of high Ti basaltic magma decreased, the melting depth and pressure decreased, resulting in the increase in melting degree. Simulation shows that the melting degree of garnet phase and spinel phase in the source area is 0.5%~2% and 5% respectively, the melting ratio of garnet phase decreases from 90% to 40% and that of spinel phase increases from 10% to 60% from west to east.

    • WANG Chang-bing, NI Guang-qing, QIN Yong-kai, LIAO Zhi-kai, LI Wei-sen, LI Shi, ZHANG Li, GUAN Bin

      2021,40(4):704-716, DOI:

      Abstract:

      The Gejiu alkaline complex is composed of alkaline feldspar syenite in border facies and nepheline syenite in central facies. The whole-rock geochemical analysis shows that the alkaline complex has the characteristics of high alkalinity, rich potassium, rich iron, low magnesium, and highly differentiated alkaline-peralkaline rocks, with the late stage more enriched in alkali metal elements. LREE/HREE=20~59, (La/Sm)N=8~50, and (Sm/Yb)N=1.2~5.0. It is rich in light rare earth elements. The fractionation degree of the light rare earth elements is higher than that of the heavier rare earth elements. It has Eu negative anomaly. The Gejiu alkaline complex is depleted in such elements as Ti, Nb, P, K, and Sr, and rich in such elements as Zr, Hf, Th, La, Ce, Nd, U and Rb. All these characteristics indicate that the magma source is related to mantle derived materials. Alkali syenite and nepheline syenite have similar characteristics of trace elements and rare earth elements, and have the characteristics of homologous magmatic differentiation and evolution. The ratios of Rb/Sr, Nb/Ta, and Zr/Hf are all higher than or close to the corresponding values of the original mantle. CIPW standard mineral calculations show that perilla pyroxene, cone pyroxene, and olivine appear in the alkali syenite in marginal facies. Olivine appears in the nepheline syenite in central facies. Combined with the characteristics of the ratios of (Th/Nb)N and Nb/La and the research results of previous Sr-Nd isotope, it is considered that the magma of Gejiu alkaline complex was derived from partial melting of enriched mantle subjected to metasomatism and limited crustal contamination, which was formed in the extensional environment of the post-collision. In the late period of alkaline magama evolution, alkali was richer, and the higher degree of crystallization differentiation constituted an important factor for the abnormal enrichment of REE, Nb, Ga and Zr.

    • AN Xiu-hui, CHENG Zhi-guo, ZHANG Zhao-chong, LIU Bing-xiang, KONG Wei-liang

      2021,40(4):717-728, DOI:

      Abstract:

      The highly fractionated high-silica rhyolite is a potential host of the rare earth elements (REE) deposits. The Tarim large igneous province (T-LIP) is characterized by a high proportion of felsic rocks; nevertheless, the potential capacity of the REE mineralization remains unclear. In this study, ignimbrite from well S42 in Northern Tarim Uplift was studied, and several Fe-P-REE enriched mineral assemblages were recognized: ① the lithoclast consisting of quartz rim and magnetite+monazite+alkali feldspar core; ② the magnetite+monazite+rutile+apatite in the groundmass; ③ the monazite+pyrite in the quartz phenocryst. Further analysis of quartz SIMS oxygen isotopes in situ showed that the δ18OV-SMOW values of lithic quartz range from 11.15‰ to 14.60‰, while those of the quartz phenocrysts are from 7.23‰ to 7.84‰, consistent with the bulk-rock oxygenic composition (5.00‰~7.21‰). A titanium thermometer of quartz shows that the formation temperature of quartz phenocryst was 756~815℃, and that of lithic quartz was 566~645℃. In addition, trace elemental compositions of magnetite associated with quartz in the lithoclast also show consistency with those of the hydrothermal origin. The above evidence indicates that the Fe-P-REE mineral assemblage in the lithoclast was derived from the late hydrothermal fluids. On the other hand, the occurrence of Fe-P-REE mineral aggregates in the groundmass of the ignimbrite and quartz phenocryst indicates that REE were sufficiently concentrated in magma and then REE minerals were crystallized in the late stage of evolution. Therefore, the Fe-P-REE enriched mineral aggregates in the ignimbrite were mainly related to the magmatic fractional crystallization and the late hydrothermal fluids. Their recognition provides an important implication for the REE mineralization of felsic rocks in the T-LIP.

    • LIAO Cheng, YANG Tian-nan, LIANG Ming-juan, XIN Di, DONG Meng-meng, XUE Chuan-dong

      2021,40(4):729-746, DOI:

      Abstract:

      The India-Eurasia collision led to the formation of an orthogonal collisional belt and an oblique collisional belt, which are the Tibet-Himalaya and the Sanjiang orogenic belts, respectively, and are now separated by the east Himalaya syntax. The Eocene Jianchuan basin is located in the southernmost region of the oblique collisional belt. Detailed sedimentary study of four profiles along the western margin of the Jianchuan basin revealed two stages of the basin infilling process, which were separated by the 37~34 Ma potassic volcanism. The earlier stage infillings were sourced from the southwest, and displayed upper and middle fan, and/then delta plain facies. The later stage infillings were derived from the northwest regions of the basin, which formed upper fan facies. Combined with the Eocene structures of the basin's basement, the authors hold that the Jianchuan basin is an Eocene foreland one. The Eocene Jianchuan foreland basin, along with its numerous equivalents in eastern and central Tibet, likely was previously located in the orthogonal collisional belt. The boundary between the orthogonal and oblique collisional belts might have been located in the south of the Jianchuan basin during the Eocene. The changes in tectonic location of the Jianchuan foreland basin indicate the successive northward growth of the oblique collisional belt due to the continuous northward indenting of the India continent into Eurasia.

    • HUANG Liang, TIAN Su-mei, ZHANG Hu, XIONG Bo, WANG Xiao-lin, PU Tao, YANG Shi-pan, FANG Xiong

      2021,40(4):747-756, DOI:

      Abstract:

      A set of meta-argillaceous rocks mainly composed of biotite plagioclase gneiss have been newly discovered in Caojian, Yunlong County, western Yunnan Province, which are existent in the form of structural lenses, with small outcrops and well-developed medium-high metamorphic minerals, which is obviously different from the feature of surrounding rocks. Petrographic study shows that gneiss has obvious mineralogical records of subduction-exhumation, and there is also a paragenetic mineral assemblage of kyanite+aluminum amphibole, and the corresponding metamorphic pressure should have reached 1.0 GPa or higher. The metamorphic temperature and pressure of rocks calculated by GBP average temperature and pressure meter method are 566~623℃ and 0.36~0.53 GPa respectively. In addition, there is a small amount of siliceous muscovite minerals in gneiss. According to the p-T visual profile of phase equilibrium simulation and the characteristics of its maximum silicon atomic weight of 3.23, it is inferred that the rock belongs to blueschist. According to the comprehensive study, the biotite plagioclase gneiss belongs to high-pressure metamorphic rocks (the minimum metamorphic pressure in peak period is about 1.60 GPa), and these data provide new information in search for high-pressure metamorphic rocks in the northern part of Changning-Menglian junction zone, and also show that Changning-Menglian junction zone is a continuous high-pressure and ultrahigh-pressure metamorphic zone.

    • YANG Hu, LUO Hong-ying, LU Kuan-wei, ZHANG Ying

      2021,40(4):757-763, DOI:

      Abstract:

      Scanning electron microscope, X-ray spectroscopy,XRD, MLA mineral detection software were used to study the material composition, modes of occurrence, embedded properties, particle size and dissociation characteristics of a copper mine. The results show that the main valuable metal in the ore is copper, possessing 1.05%, which mainly occurs in chalcopyrite, bornite, chalcocit and malachite. The gangue minerals mainly include quartz and feldspar, followed by calcite and chlorite. The grain size of the main minerals is less than 20 μm, and the metal content of -9.6 μm is 0.3%. The degree of liberation is low. Moreover, the main copper minerals have close association with gangue minerals, reaching more than 40%. It is difficult to achieve a good economic index only by flotation. Based on the results of process mineralogy research, the authors adopted one roughing process- two cleaning processes- two scavenging flotation intensification processes to carry out closed-circuit test for part of the scheme of centralized treatment of middle ore. The copper grade and recovery of copper concentrate are 19.12% and 79.16%.

    • 综述与进展
    • HU Han, ZHANG Li-fei

      2021,40(4):764-777, DOI:

      Abstract:

      Graphitic carbon is mainly transformed from organic compounds or carbonate minerals in nature, and can exist stablly in sedimentary rocks, magmatic rocks and metamorphic rocks. With the development of research on the carbon cycle in subduction zones, graphitic carbon, which usually occurs as accessory mineral in metamorphic rocks, has increasingly attracted attention. Graphitic carbon can be stable in subduction zones as carbon sinks due to its low solubility with respect to carbonate and the low mobility with respect to carbonic fluids. However, graphitic carbon can be reactive under some special geological conditions (e.g., with the presence of aqueous fluids in open systems), and becomes active and migrates. Therefore, graphitic carbon is one of the key subjects to trace carbon cycle in subduction zones. Based on previous studies, this paper provides an overview of the properties, formation, and decomposition of graphitic carbon in subduction zones, and comprehensively discusses the abiotic genesis, the stability and the release of them, which can be a key participant in the carbon cycle in subduction zones. There are three main genetics mechanisms of graphitic carbon in subduction zones: graphitization of biological organic matter, precipitation of saturated carbonic fluid, and reduction of carbonate minerals. Graphitic carbon in subduction zones can be released through degassing and fluid-mediated dissolution. Subduction and weathering erosion are the two main processes in the global cycle of graphitic carbon, with subduction having a greater impact on the internal circulation of graphitic carbon.

    • ZHANG Ming, XIE Jing-li

      2021,40(4):778-785, DOI:

      Abstract:

      During the service of the high-level radioactive waste repository, low-carbon steel serves as a candidate metal material for the disposal tank, but iron corrosion products infiltrate into the buffer barrier, resulting in mineral phase transformation and performance variation, which threatens the long-term safety and stability of the multiple barrier system. This paper reviews the chemical and low-medium temperature field in the deep reduction environment of the repositories. It is believed that the above factors can cause the release of Fe2+ in the disposal tank. Fe2+ causes montmorillonite mineral phase transformation: Fe2+ replaces Al3+ and Mg2+ in the octahedral lattice of montmorillonite, reduces Fe3+ or directly occupies the vacancy to generate secondary minerals; Fe2+ exchanges Na+, K+ and Ca2+, converted to iron-based montmorillonite. Mineral phase transition can induce buffer barrier performance variation or even degradation. Based on the concept of "resisting mineral transformation", the research direction of the mineral phase transformation of the buffer material in the next stage is proposed, which provides a scientific basis for the selection of carbon steel in underground laboratories, the design of the verification test of the buffer barrier and the safety evaluation of the barrier system.

    • 环境矿物学
    • HUA Min, ZHANG Di, JIANG Ai-ling, XIONG Hui-xin

      2021,40(4):786-794, DOI:

      Abstract:

      The low molecular organic sodium commonly existed in the environment can affect the biomineralized products (schwertmannite and jarosite) of Acidithiobacillus ferrooxidans (A. ferrooxidans), which can lead to changes in the migration and transformation of toxic heavy metals in the environment. This paper discussed the influence of low molecular organic sodium salts on the bacterially metabolized iron minerals during the growth process of A. ferrooxidans HX3, and also characterized and analyzed the iron minerals by XRD, FTIR, FESEM and EDS. The study results showed that the addition of low molecular organic sodium salts at the lower concentrations had unobvious effects on the Fe2+ oxidation, but it could accelerate the formation of jarosite. Addition of sodium malate was conducive to the transformation of schwertmannite to jarosite, compared with addition of sodium citrate or sodium oxalate. Addition of the low molecular organic sodium salts at the higher concentration (i.e. 20, 40 and 40 mmol/L for sodium malate, sodium citrate and sodium oxalate, respectively) inhibited the oxidation of Fe2+ during bacterial cultivation process. The sequence of inhibitory effects from large to small was following: sodium malate>sodium citrate>sodium oxalate. These results could provide a theoretical reference for the formation and transformation of iron minerals in acid mine wastewater containing iron bacteria such as A. ferrooxidans, and their biomineralization mechanism.

    • TAO Ling, LIU Wei, LIU Rui-zhen, SHANG Qian-qian, HE Jing, REN Jun

      2021,40(4):795-803, DOI:

      Abstract:

      To explore the stabilization effect of palygorskite activated by different concentrations of H2SO4 solution on Cd in soil, the authors carried out acid activation of palygorskite by using H2SO4 solutions with concentrations of 5%, 7.5%, 10%, 12.5% and 15%, respectively. Stabilization experiments and pot experiments were carried out with the addition of Cd contaminated soil. The results showed that the active Cd content of soil was significantly reduced by applying palygorskite activated by different concentrations of H2SO4 solution, and that the stabilization effect of 10% H2SO4 activated palygorskite was the most significant. The extracted Cd content of toxic leaching (TCLP) and diethylene triamine pentacetic acid (DTPA) decreased by 31.11% and 37.33%, respectively. The results of continuous extraction by the European Community Reference Agency (BCR) showed that palygorskite modified by acid can significantly reduce the content of acid-soluble state and reduction state of Cd in soil. The palygorskite modified by acid could significantly inhibit the absorption of Cd in soil and the transfer of underground part to the aboveground part. The content of Cd in the surface part of maize decreased by 26.99%~43.97% compared with the control group, and the content of Cd in the underground part of maize decreased by 15.36%~27.40% compared with the control group. Palygorskite modified by acid has obvious stabilization effect on Cd in soil.

    • LIN Yan-hui, BIAN Liang, SONG Mian-xin, LI Hai-long, LI Yu, LUO Wei-ge, ZHANG Jiao, ZHANG Jin-mei, LUO Wei-hui, ZHANG Qin

      2021,40(4):804-811, DOI:

      Abstract:

      In order to study the heterogeneous oxidation mechanism of SO2 on γ-Al2O3 (110) surface by HONO, the authors calculated the adsorption and oxidation mechanism of SO2 and HONO on γ-Al2O3 (110) surface by the first principles based on density functional theory (DFT). The results showed that SO2 was adsorbed on the perfect/defect γ-Al2O3 (110) surface in the form of molecules, while HONO existed only on the perfect surface in the form of molecules. The existence of oxygen vacancies on the surface not only enhanced the adsorption strength of SO2 and HONO, but also induced the decomposition of HONO on the oxygen defect surface (HONO→NO + ·OH). The analysis of partial density of states (PDOS) and Mulliken charge distribution showed that the decomposition of HONO follows the Haber-Weiss mechanism. It is found that SO2 and HONO were adsorbed on the oxygen defect surface, and the OH radicals generated by HONO decomposition oxidized SO2 to form HOSO2 cluster molecules. This study not only helps to understand the role of HONO in the oxidation of SO2 on the surface of mineral oxides, but also provides a theoretical basis for explaining the formation of atmospheric sulfate aerosols.

    • 宝玉石矿物学
    • XING Ying-ying, QI Li-jian

      2021,40(4):812-824, DOI:

      Abstract:

      Based on the fact that multi-stage fluid activities play an important role in the interaction between jadeitite and symplectitic coronas, the authors focused on the study of the composition and the mode of occurrence of water in the symplectitic coronas of amphibole + chromite jadeite + jadeite in Myanmar amphibolite jadeitite from the micro scale point of view. The results show that the fluid composition involved in the formation of symplectitic coronas is complex and the formation process is of multi-stage. The paragenetic minerals of symplectitic coronas are different, the chemical composition zone of amphibole+ chromite jadeite + jadeite is widely developed in amphibolite jadeitite. In addition, the structural hydroxyl content of amphibole is more uniform in the core of symplectitic coronas, and from the edge of chromite jadeite to jadeite the structural hydroxyl content increases regularly. The change regularity of structural hydroxyl content further indicates that the formation environment of the symplectitic coronas in Myanmar jadeitite is relatively stable, which is dominated by multi-stage fluid metasomatism, without large-scale dynamic metamorphism. The evolution of the composition and water content of symplectitic coronas in Myanmar jadeitite is helpful to understanding the interaction trajectory of the fluids in the subduction zone in this area and providing some evidence for the diagenetic mechanism of Myanmar jadeitite.

    • ZOU Yu, LI Peng, WU Zhi-ying, KANG Meng-ling, WANG Shi-qi

      2021,40(4):825-934, DOI:

      Abstract:

      The petrological characteristics of Sangpiyu tremolite jade from Xiuyan County of Liaoning Province were studied using polarizing microscope and electron probe microanalysis (EPMA). The zircon and titanite grains which are separated from Sangpiyu tremolite jade were dated by secondary ion mass spectrometry (SIMS). The results show that Sangpiyu tremolite jade is mainly composed of tremolite, and its secondary minerals mainly include apatite, calcite, chlorite, graphite, limonite, zircon and titanite. Under polarized light microscope, the main textures of Sangpiyu tremolite jade are felt-like fiber interweaving texture, micro-fine crystalline texture and fibrous metamorphic texture. The main structure is massive structure. The main chemical components of Sangpiyu tremolite jade are SiO2, MgO and CaO. The ratio of Mg2+/(Mg2++Fe2+) ranges from 0.964 to 0.971. The zircon 206Pb/238U age of Sangpiyu tremolite jade is 1 851±7 Ma, and the titanite207Pb/206Pb age is 1 848±17 Ma. The Sangpiyu tremolite jade was formed in the dolomite during the period of palao-Proterozoic regional metamorphism.

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    Volume 40,2021 Issue 4
      专题研究
    • ZHANG Li-cheng, WANG Yi-tian, CHEN Xue-feng, MA Shi-qing, WANG Zhi-hua, YU Chang-fa

      2013,32(4):431-449, DOI:

      Abstract:

      The Hongyuntan iron deposit is hosted in pyroclastic rocks of the Lower Carboniferous Yamansu Formation. The ore bodies occur as layers, stratoid bodies or lenses. The principal ore mineral is magnetite, together with minor maghemite, specularite, pyrite and trace chalcopyrite. The gangue minerals include garnet, diopside, actinolite, chlorite, tremolite, epidote, biotite, albite and quartz. The ore structures are mainly of massive and disseminated forms, with occasional banded or veined forms. The ore textures are of subhedral-anhedral granular and metasomatic types. The wall rock alteration shows symmetrical zoning, and the alteration colors change from dark to light from ore bodies outwards. On the basis of observed mineral assemblages and ore fabrics, two periods of ore deposition were recognized, i.e., skarn period and hydrothermal ore-forming period, which could be further subdivided into four metallogenic stages, namely skarn stage, retrograde alteration stage (main ore-forming stage), early hydrothermal stage and quartz-sulfide stage. Electron microprobe analyses show that the end member of garnet is mainly andradite-grossularite. The composition of pyroxene is mainly diopside-asteroite. The amphiboles is composed mainly of actinolite and tremolite with minor magnesiohornblende. The composition of these skarn minerals suggests that skarn in the Hongyuntan iron deposit is calcic skarn, belonging to metasomatic skarn. The characteristics of main and trace elements suggest that the formation of magnetite was closely related to the skarn. In combination with geological characteristics, the authors suggest that the skarn might have resulted from interaction between Ca-rich pyroclastic and Fe-rich magmatic hydrothermal fluid which was transported along the fault system. The formation of magnetite was hence related to the regressive metamorphism of the skarn.

    • Gan Guoliang Yichang Institute of Geology, Mineral Resources, Chinese Academy of Geological Sciences Department of Grologicol, Atmospheric Sciences, lows State Univeraity, Ames, IAS0011, U.S.A

      1993,12(2):144-181, DOI:

      Abstract:

      This paper presents partition coefficients of 69 chemical elements (Li, Rb,Cs, K, Na, Ca, Ba, Sr, Mn, Fe, Mg, Cu, Pb, Zn, Co, Ni, Be, La, Ce, Nd,Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Sc, Cr, In, Ga, Al, B,Cd, Sb, Bi, U, Th, Zr, Hf, Si, Ti, Ge, Sn, Mo, Nb, Ta, W, V, P, F, Cl,S, N, O, C, As, Pu, Re, Os, He, Ne, Ar, Kr and Xe) and the univalent radical (OH) in 28 minerals (olivine, clinopyroxene, orthopyroxene, amphibole,biotite, Phlogopite, plagiocla-se, K--feldspar, quartz, magnetite, ilmenite, garnet,zircon, apatite, allanite, topaz, sphene, cordierite, hauyne, leucite, nepheline,whit-lockite, brookite, petovskite, melilite, armalcolite, spinel and rutile) from 8 types of rocks, namely metaluminous (ultra) basic rock, peralkaline (ultra) basic rock, metaluminous intermediate rock, peralkaline intermediate rock,metaluminous acid rock, peralkaline acid rock, peraluminous acid rock and ultra-acid rock. It is found through an integrated ahalysis and comparison that the composition and structure of minnerals and melts seem to be the most important factors controlling mineral-melt element partitioning. Importanceshould be attached to minral structure and Al-supersaturation of melt which have, not been discussed by research workers. Finally, the present state and theproblems to be solved in the study of mineral--melt element partition coefficients are analysed, and the future trends of this research field are predibted.

    • 综合资料
    • SHEN Qi-han

      2009,28(5):495-500, DOI:

      Abstract:

      This paper has mainly recommended a mineral abbreviation list (see Table 2 and Table 3). Table 2, which contains 243 minerals, was compiled by IUGS Subcommittee on the Systematic of Metamorphic Rocks (SCMR) in 2007. The author selected other 29 minerals and, on such a basis, formulated Table 3. Thus, the total mineral abbreviations come to 272. It is hoped that they can be popularized in future and become more and more perfect through utilization, so as to provide a basis for ultimate standardization and unification.

    • 专题研究
    • HE Shi-ping, WANG Hong-liang, XU Xue-yi, ZHANG Hong-fei, REN Guang-ming

      2007,26(4):295-309, DOI:

      Abstract:

      Early Paleozoic volcanic rocks in Tianshui and Baoji areas along the eastern segment of North Qilian orogenic belt consists of Hongtubu basaltic lavas and Chenjiahe intermediate-acid volcanic rocks. Geochemical analyses show that Hongtubu basaltic lavas are similar to the intercalated basalts in Chenjiahe intermediate-acid volcanic rocks in characteristics, both fallen in the tholeiite series with high TiO2 (1.50%~2.73%). Their∑REE are 65.97×10-6~133.46×10-6 and 78.04×10-6~175.55×10-6 respectively, both are slightly enriched in LREE [(La/YbN being 2.00~4.40 and 2.71~4.40 respectively],and both have no obvious Eu anomaly or weak Eu negative anomaly(δEu being 0.85~1.10 and 0.85~0.99 respectively). Basalts from two groups are typically characterized by selected enrichment of LILEs, low abundances of HFSEs relative to NMORB, and prominent troughs of Nb and Ta, with low Nb/La ratio(0.28~0.43), which indicates the affinity of these volcanic rocks to island arc tholeiite(IAT). In addition, εNd(t)(+2.22~+4.08)values of basalts suggest that their mantle sources are similar to the depleted mantle source. Zr/Nb=17.21~36.33 and Ce/Nb=5.73~8.17, implying geochemical characteristics of N-MORB. Sr, Nd and Pb isotopes from Hongtubu basalts are similar to those in Chenjiahe basalts in composition. In the diagrams of εNd(t)-(87Sr/86Sr)t, (207Pb/204Pb)t-(206Pb/204Pb)t,(87Sr/86Sr)t-(206Pb/204Pb)t and εNd(t)-(206Pb/204Pb)t for basalts, the data are fallen in the DM, EMⅠand EMⅡ areas, probably with a little crustalontamination, indicating that the magma of basalts might have had a mixed gin.Thentermediate-acid volcanic rocks from Chenjiahe belong to the calc-alkaline series,they have relatively high abundances of REE∑REE=127.51×10-6~276.01×10-6), and are significantly enriched in LREE[(La/YbN= 4.79~13.51]. Most intermediate-acid volcanic rocks show weak Eu negative anomaly (δEu=0.53~1.20). The trace element patterns of Chenjiahe acid volcanic rocks are similar to those of the ocean ridge granite (ORG), with marked troughs of Nb, Ta, Zr and Hf. A synthetic study shows that the Chenjiahe intermediate-acid volcanic rocks in the eastern segment of North Qilian orogenic belt were formed in an island-arc setting, whereas the Hongtubu basalts were formed in an intra-arc rift setting (or an initial back-arc basin setting), probably being products of the early spreading evolution of the island_arc system towards the back-arc basin in the eastern segment of North Qilian during late Early Paleozoic. The results obtained provide evidence for the existence of the trench-arc-basin system at the juncture of Qilian and North Qinling orogenic belts.

    • 宝玉石矿物学
    • YAN Ruogu, QIU Zhili, DONG Chuanwan, LI Liufen

      2009,28(3):292-298, DOI:

      Abstract:

      High grade black jadeite is a kind of upscale and fashionable jade material that has become one of the jadeites characterized by fastest growing values in the past 20 years. Based on a comparison of mineralogical and geochemical characteristics between black jadeites (inky black jades)from different producing areas of the world, the authors hold that the black jadeites currently on the market can be mainly classified into jadeite jade, omphacitic jadeite jade and hornblende jade whose main components are jadeite, omphacite and dark green hornblende respectively. They include black chicken jade, ink jadeite and black kosmochlor from Myanmar and jade negro and galactic gold from Guatemala, with black chicken jades similar to those from Myanmar also seen in Japan and Kazakhstan. The research results suggest that the main mineral composition, jade structure and inclusion characteristic combinations of black jadeite jades from different producing areas have their respective typomorphic natures, which can be used as the distinctive characteristics for their sources.

    • 综述与进展
    • ZHANG Wei

      2014,33(4):747-762, DOI:

      Abstract:

      Cordierite is a mineral material characterized by low thermal expansion coefficient and good thermal shock resistance. Cordierite mineral material is relatively rare in nature, so cordierite is synthesized usually by the method of artificial synthesis. Based on the newest investigation results of synthetic cordierite, this paper deals with the progress of researches on such synthesis methods of cordierite as high purity oxide solid reaction at high temperature, natural mineral solid reaction at high temperature, the utilization of industrial wasted materials, the employment of agricultural wasted materials, the sol-gel and the low-temperature combustion synthesis. At present, the method of natural mineral solid reaction at high temperature is used for the preparation of cordierite in industry. In spite of a lot of advantages, this method also has many disadvantages. Therefore, the development trend of cordierite synthesis seems to solve the problem as to how to apply other synthesis methods to industrial preparation.

    • 专题研究
    • CAO Guang-yue, XUE Huai-min, WANG Jin-guang

      2014,33(6):1019-1038, DOI:

      Abstract:

      In this paper,LA-ICP-MS zircon U-Pb dating was carried out for four samples of volcanic rocks from Qingshan Group in Jiaodong area and, as a result, their concordant ages were obtained, which are 119.4±0.9 Ma, 118.2±1.0 Ma,120.2±0.9 Ma and 120.0±0.8 Ma, respectively. The results show that all the volcanic rocks in Jiaodong area were formed from about 120 Ma to 118 Ma in the Early Cretaceous period. The ages of Qingshan Group volcanic rocks from Shandong Province controlled by Tan-Lu fault are similar to those from the Su-Wan segment of the Tan-Lu fault zone,but younger than those around the Tan-Lu fault zone,which indicates that the duration of volcanic eruption along Tan-Lu fault is probably longer than the duration in other areas under the background of lithospheric thinning in eastern China. Geochemically, all the intermediate and acidic volcanic rocks have high K2O, ALK, LREE values and low MgO, TiO2, Ni, Cr, HREE values. According to the geochemical features, the volcanic rocks can be subdivided into trachyte-trachydacite and rhyolite. The trachyte-trachydacite is characterized by LILE enrichment(Rb,Ba,K)and HFSE depletion(Nb,Ta,Ti,P), but the rhyolite exhibits stronger depletion of Ba,Sr and HFSE (Ti,P). Compared with the rhyolite,the trachyte-trachydacite possesses higher Sr and Ba values as well as La/Nb and Ba/Nb ratios,but lower Rb/Ba ratios and δEu values. All these data indicate that they might have been derived from different magma sources. It is inferred that the trachyte-trachydacite rocks were derived from the mixture of the partial melting of the lower crust(Yangtze Craton or North China Craton)and enriched lithospheric mantle. In addition, the rhyolites were related to the partial melting of the lower crust in the regional extension environment and high geothermal anomaly background with crystallization differentiation during the magma evolution.

    • 宝玉石矿物学
    • GUO Li-he, HAN Jing-yi, LUO Hong-yu

      2006,25(4):349-356, DOI:

      Abstract:

      At present, the infrared transmission spectroscopy is the best technique for determining whether jadeite is polymer-impregnated or not, and the infrared reflectance spectroscopy is a nondestructive and rapid determination method that provides mainly the fundamental frequency vibration spectra data of minerals and shows new application potentials in gemological research, especially in the identification of gem species. The gemological application of IR reflectance spectroscopy and the identification system of IR spectra of gems, including a database of 318 spectra and a searching and identifying program, are described in this paper.

    • 专题研究
    • LIN Guang-chun

      2013,32(4):485-495, DOI:

      Abstract:

      Petrology, geochemical and Nd isotopic data are reported for the Neoproterozoic Danba metabasalt in the Kangdian Rift on the western margin of the Yangtze block. Samples were collected from alkaline basalts, which are enriched in MgO, TiO2, with Mg# being 0.51~0.59. They have high total rare earth elements and show high fractionation between LREE and HREE. The trace elements are characterized obviously by enrichment of Th, Nb, Ta, Zr, Hf and LREE but depletion of Y and HREE. Their geochemical and Nd isotopic characteristics suggest that they are similar to OIB. The basaltic magma was generated in an intraplate setting, and was generated by partial melting of OIB mantle source region, with variable degrees of contamination of SCLM during magma ascending; in addition, some samples might have experienced contamination of the lower crust. These samples reveal some plume magmatism characteristics in petrochemistry, and imply that magmatism was probably related to the Neoproterozoic plume event, which resulted in the breakup of Rodinia supercontinent.

    • ZHANG Kan, ZHU Xiang-kun

      2013,32(4):529-537, DOI:

      Abstract:

      The newly-exposed lower strata of the Xiamaling Formation near Tielingzi Village in Jixian County contain rich siderites. This paper reports the basic geological characteristics of these siderite-rich strata in terms of the field outcrop, petrology and major elements. Studies show that the profile is characterized by black shale interbedded with silty iron-rich layers/siderite concrete layers, and also has minor siltstone. Some iron-rich strata have turned into limonite layers in the outcrop because of intense weathering. Siderite is the main iron mineral phase in the strata. Siderites can form iron concretes, showing micritic or microcrystalline granulitic textures under the microscope, or form silty ferruginous layers with almost a comparable amount of silty quartz; it can also distributed sporadically in siltstone and black shale with relatively coarse particles. There also exists very little siderite residue in weathered limonite layers. The overall features of major elements show that the strata are rich in SiO2, TFe and TOC, but poor in MnO, CaO, MgO, P2O5 and S. Except for ferriciron in weathered layers, there is mainly ferrous iron in the strata. The TOC content decreases in order of siderite concrete, silty iron-rich layer, black shale and siltstone. The correlation diagram between TFe and Al2O3 content shows a negative correlation in iron-rich layers, while a positive correlation between them exists in normal black shale and siltstone, which suggests that iron in the former form originated from the ocean itself, while iron in the latter form originated mainly from terrigenous detritus. In addition, FeO content has a positive correlation with TOC content in fresh samples, which implies that the genesis of siderites may have some relationship with organic matter.

    • Zhou Zheng

      1997,16(1):81-90, DOI:

      Abstract:

      From the discovery of the first new mineral hsianghualite in 1958 to the end of 1995,74 new minerals found in China had been approved by IMA CNMMN. Among them, 2/3 were discovered after 1981. The discovery of new minerals in China has the following features:(1) With the development of analytical methods, the number of new minerals discovered per year increases gradually: from the end of 1950s to 1960s, only one new mineral was discovered every year on the average, whereas from 1980s till now, three new minerals were discovered averagely every year. (2) The structures of many new minerals have been determined. (3) Most of the new minerals are in the lower category, mainly in the monoclinic system, and perfect crystals are rare; hsianghualite has the most abundant crystal faces, whose ideal faces can reach 146. (4) Among those new minerals, silicates take the first place in number, followed by native elements, alloys, and then oxides. (5) The modes of occurrence of new minerals are varied, most of them occurring in oxidized zones of various deposits and deposits related to ma fic or ultramafic rock masses. There are a few new minerals occurring in skarn and placer deposits or even in cosmic dusts and meteorite.(6) The new minerals are characterized by wide but uneven distribution. Till now, new minerals have been discovered in 20 provinces or autonomous regions, especially in Hebei, Qinghai, Inner Mongolia and Henan. The number of new minerals found in North China is larger than that found in South Chine. (7) The number of discoverers of new minerals is in tens. The first discoverer of new mineral is Prof. Huang Yunhui, whereas Prof. Yu Zuxiang is the one who discovered the most numerous new minerals in China, totally disclosing 11 new minerals by himself or together with other experts. Most of the discoverers are members of the Chinese Academy of Geological Sciences, China University of Geosciences, and Institute of Geochemistry, Academia Sinica as well as other educational and scientific research institutions. The discovery of new minerals has promoted the development of mineralogy in China. Tens of discoverers were awardees of the National Natural Sciences Prize or the Science and Technology Progress Prize of the Ministry of Geology and Mineral Resources for the discovery and research results of new minerals in 1980s. More than 60 new mineals discovered in China were collected by the Geological Museum of China, with some of them exhibited in the Minerals and Rocks Exhibiting Room.

    • 其他
    • LUO Yue-ping, DENG Wang-hui, DUAN Ti-yu, WANG Chun-sheng

      2011,30(Z1):181-186, DOI:

      Abstract:

      As more and more treated turquoises appear on Chinese gem market, the authors collected lots of turquoises from different deposits on Chinese gem market in order to sum up the characteristics of the natural turquoises on Chinese gem market. At the same time, different types of treated turquoises were studied to find general difference between them and natural turquoises. The results show that natural turquoise and treated turquoise have different shades of color, inclusions and appearances. IR spectra of both natural and treated turquoises were studied, indicating that there are absorption peaks at 1 735, 1 600 and 1?500 cm-1 in treated turquoises, which are caused by the man-made polymer. If the turquoise is treated by polymer, there are absorption peaks at 1 735, 1 600 and1 500 cm-1 in a turquoise, and this can serve as convincing evidence in this aspect.

    • 专题研究
    • ZHU Xin-you, WANG Yan-li, CHENG Xi-yin, TIAN Ye

      2016,35(1):16-32, DOI:

      Abstract:

      There are several types of xenoliths, such as monzonite, quartz diorite porphyry, black rock and greisen schlieren, in the alkali feldspar granite of the Yaogangxian tungsten deposit, Hunan Province. The xenoliths are different in geological and geochemical characteristics, sources and evolution paths, which implies the genesis and magma evolution history of the Yaogangxian granite. In this paper, the authors studied the petrology, geochemistry of the xenoliths, alkali feldspar granite, and monzonite batholiths formed in late Jurassic period. It is detected that the monzonite inclusion (Ⅰb) came from early crystallization of deep magma chamber similar to the monzonite batholith. The quartz diorite porphyry and black rock xenoliths seem to have been the residue of Precambrian metamorphic rocks in the melting. The greisen schlieren resulted from the transition from the alkali feldspar granite stage to the magma-hydrothermal stage. The fine biotite granite xenolith (Ⅲb) in the quartz porphyry was captured from the supplementary granite which was differentiated from the main magma, or from the granite pluton formed from the supplementary rocks. The granite (Ⅰ) was rich in volatiles, which resulted in strong contamination of the xenoliths, and a certain amount of fluorite, mica, tourmaline and sulfide minerals formed in the xenoliths. The Yaogangxian granite is a product of the intrusion of highly fractionated magma derived from the magma chamber equivalent to monzonite batholith. The quartz porphyry magma directly resulted from the residue of segregation from fractional crystallization of magma chamber, rather than from the alkali feldspar granite of Yaogangxian. It is suggested that the magma evolved in order of magma chamber (main) (coarse monzonite) → fine biotite granite (supplementary) → alkali feldspar granite → magma-hydrothermal transition fluid (tungsten mineralization) → quartz porphyry veins.

    • LI Yu-long, YANG Zhu-sen, TIAN Shi-hong, ZHAO Zhi-yi, LU Shi-yin, ZHANG Yao, LIU Ying-chao

      2015,34(5):648-664, DOI:

      Abstract:

      Two kinds of carbonate hosted Pb-Zn deposits, namely carbonate-rich Pb-Zn deposits and fluorite-rich Pb-Zn deposits, extensively exist in the same Pb-Zn metallogenic belt in the world according to the classification based on gangue mineral assemblages. The relationship between the two kinds of deposits remains unclear. In the middle part of the 'Sanjiang' metallogenic belt in the Tibetan Plateau, the Dongmozhazhua carbonate-rich Pb-Zn deposit and the Mohailaheng fluorite-rich Pb-Zn deposit occur in the same carbonate-hosted Pb-Zn ore concentration area. In the two deposits, the carbonate strata are host rocks, the thrust faults are the main ore-controlling structures, the main orebody attitudes are of stratabound type, and sphalerite and galena are the main ore minerals. However, calcite and dolomite are the main gangue minerals in the Dongmozhazhua deposit while calcite and fluorite are the main gangue minerals in the Mohailaheng deposit. The geochemical features of rare earth elements (REE) in calcium-bearing minerals are different in the two deposits. The REE values of calcite in the Dongmozhazhua deposit are mainly characterized by obvious fractionation of LREE and HREE, enrichment of LREE, negative Eu anomalies and 'V'_shaped curves of chondrite-normalized REE patterns with right deviation. In contrast, the REE values of calcite and fluorite in the Mohailaheng deposit are chiefly characterized by no obvious fractionation between LREE and HREE, negative Eu anomalies and 'M'_shaped curves of chondrite-normalized REE patterns with right deviation. The total concentrations of REE (∑REE) of calcite (0.46×10-6~10.79×10-6) in the Dongmozhazhua deposit are higher than those in the Mohailaheng deposit (0.25×10-6~5.88×10-6). The geochemistry of the REE indicates that calcium-bearing minerals in the two deposits were all precipitated from a kind of hydrothermal fluids which had nothing to do with igneous activities. The salinity and reducibility of the fluids decreased with the sulfide precipitation. The two kinds of deposits had similar hydrothermal fluids; nevertheless, there existed another kind of fluid for the Mohailaheng deposit, which was a kind of fluorine-rich fluid from deep metamorphic basement. This fluorine-rich fluid controlled the location of the fluorite-rich carbonate hosted Pb-Zn deposits and could be used to explain the phenomenon why this kind of Pb-Zn deposits were more easily precipitated near the main thrust faults and the lowest carbonate strata in the region. The result achieved by the authors could answer the question why the carbonate-rich Pb-Zn deposit and the fluorite-rich Pb-Zn deposit can occur in the same region and same time in the world.

    • ZHANG Wen, WU Tai_ran, HE Yuan_kai, FENG Ji_cheng, ZHENG Rong_guo

      2010,29(6):719-731, DOI:

      Abstract:

      Beishan area is located in the west of Inner Mongolia and Gansu Province, which is the conjunction zone of Tarim plate, Sino-Korea plate and Kazakhstan plate and plays an important role in the study of the Central Asia Orogenic Belt (CAOB). The relationship of the three plates is so complicated that there exists much controversy concerning Paleozoic tectonic evolution in this area. Granitoids, especially Late Paleozoic granitoids, are widely distributed in Beishan area, which are of great importance in the study of Paleozoic magmatic evolution. Through analyzing the spatial and temporal distribution of the Late Paleozoic granitoids, we can find the relationships between these granitoids and explore the crust-mantle interaction in Beishan area during Late Paleozoic, which is important for determining the geotectonic evolution of this area. In the southern belt of Beishan, the most important tectonic event in Permian is the formation of Yin'aoxia rift zone, which makes the study of Late Paleozoic evolution more complex. The results of studying Xijianquanzi granite lying in the southern belt of Beishan in such aspects as major elements, trace elements, REE and LA-ICP-MS zircon U-Pb geochronology have provided new evidence for regional tectonics. The LA-ICP-MS zircon U-Pb age of Xijianquanzi granite is 266.1±2.2 Ma, and the Hf modal ages are 746~871 Ma. εHf(t) values are +1.3~+4.7 with an averageof +2.7, which implies the mixture of crustal and mantle.derived magmas. This feature coincides with that of other areas in the Central Asia Orogenic Belt (CAOB). Therefore, the granites in the belt may have similar magma sources. The granitic body mainly consists of monzonitic granites which belong to alkaline series with high content of SiO2 (74.33%~76.67%), Na2O+K2O (9.26%~9.57%, NK/A=0.9~1.08) and K2O (Na2O/K2O<1) . In addition, chondrite-normalized REE patterns and primitive mantle normalized geochemical patterns of all samples are approximately parallel to each other, which shows that they evolved from the same magma source. Chondrite-normalized REE patterns of the intrusive body are of “V" types and show enrichment of light rare earth elements (LREE) with low ratio of (La/Yb) N (3.18~5.29) and negative Eu anomalies (δEu =0.10~0.16). Except for Eu, the abundance of rare earth elements are demonstrably over 10 times that of chondrite. Depletion of Nb, Ba, Sr, Ti, P and enrichment of Rb, Th, K can be seen in the spidergram. Based on regional geological and geochemical characteristics, the authors have reached the conclusion that the Xijianquanzi intrusive body is an alkali-rich potassium-high granite which is a mixed product of crustal and mantle-derived magmas and was formed at the stage of rifting in the post-collisional extensional period, affected greatly by Yin'aoxia rift zone. This implies that the area entered into the stage of rifting in Middle Permian.

    • 综合资料
    • ZHANG Xi-huan, REN Yu-feng

      2008,27(2):135-151, DOI:

      Abstract:

      本文以表格的形式列举了经国际矿物学协会(IMA)新矿物与矿物命名委员会(CNMMN)批准、并于2003年度正式发表的新矿物共55种,其中硅酸盐31种,磷酸盐5种,砷酸盐2种,硫酸盐4种,硫化物3种,碳酸盐2种,钒酸盐2种,硼酸盐1种,硒化物1种,硫盐1种,氧化物1种,氢氧化物1种,复杂卤化物1种.文中表格依次列出了矿物的中外文名称及化学式、晶系及晶胞参数、主要粉晶数据、物理性质、光学性质、产状及共生(伴生)组合等.

    • 中国大陆环境典型斑岩型矿床成矿规律和找矿模型:研究进展(Ⅱ)专辑
    • ZHOU Jin-sheng, JI Xian-hua, YANG Zhu-sen, HOU Zeng-qian, ZHUANG Liang-liang

      2015,34(4):557-567, DOI:

      Abstract:

      In the magma-related deposits, the ore-forming plutons generally experienced high-degree evolution and differentiation, so its petrologic and geochemical characteristics can only reflect the final state of magma evolution. The evolution of ore-hosted magma and the geochemical behavior of main metallogenic elements in the evolution remain unclear. However, the study of contemporaneous and sympatric magmatic rocks provides a potential solution for this question. Here the authors made a case study of the northern Gangdise Pb-Zn ore belt in Tibet formed in the early period of continental collision. Based on the statistical study of lots of published geochemical analyses of magmatic rocks from the Gangdise belt, this paper presents the evolution of magma and its control of metallogenesis. The results suggest that, besides the crystallization differentiation of magma itself, crustal contamination was another factor controlling the evolution from basic magma to acid magma during differentiation. It is also found that most of the magmatic rocks formed in the early period of continental collision are less oxidized and less hydrous; nevertheless, when magma evolved to the middle and late period, the oxidation of magma increased with progressive evolution. Mantle-derived magmas are enriched in S and H2O, which experienced underplating at the base of Zn-enriched crust materials and induced partial melting. Crust-derived magmas experienced high-degree evolution, and finally resulted in the formation of the northern Gangdise Pb-Zn ore belt.

    • 综合资料
    • AI Yu-jie, FAN Guang

      2015,34(1):117-128, DOI:

      Abstract:

      This paper presents a collection of 31 new uranium minerals approved by the Commission on New Minerals, Nomenclature and Classification (CNMMN) of the International Mineralogical Association (IMA) between January 2003 and December 2013. It lists the mineral names both in English and Chinese together with their structural formulae, crystal structure data, physical and optical properties, localities and modes of occurrence. The crystallochemical classification and characteristics of these new minerals are discussed. Some suggestions are put forward concerning China's uranium minerals research work in the hope of providing valuable reference for China's uranium researchers.

    • 专题研究
    • SHI Jian-rong, LIU Fu-lai, LIU Ping-hua, MENG En, LIU Chao-hui, YANG Hong, WANG Fang, CAI Jia

      2014,33(1):29-50, DOI:

      Abstract:

      Eclogites and blueschists are exposed mainly as slices or variable tectonic lenses within garnet phengite schists in Habutengsu area, southwestern Tianshan Mountains, Xinjiang. In this paper, petrography, mineralogical chemistry and p-T conditions of the eclogites and blueschists were studied in detail. The eclogites could be divided into four groups, i.e., glaucophane eclogites, paragonite eclogites, epidote eclogites, and glaucophane-garnet amphibolites (retrograde eclogites), whereas blueschists could be divided into three groups, namely glaucophane-bearing garnet-muscovite-albite schists, garnet-muscovite-glaucophane schists and garnet-muscovite-glaucophane-quartz schists. Major mineral assemblages are Grt+Omp+Pg+Ep for the fresh eclogites, Grt+Gln+Amp for the retrograde eclogites, and Grt+Gln+Phe+Pg+Ab+Qtz for the blueschists. Porphyroblastic garnets show perfect prograde zoning, with XMn and XFe deceasing and XMg and XCa increasing from the core to the rim, which indicates a process of increasing temperature and prograde metamorphism. According to the paragenetic assemblages of inclusions within garnet as well as in matrix, four stages of metamorphism were recognized, viz., pre-peak lawsonite-blueschist facies metamorphic stage, peak eclogite facies stage (t=543~579℃, p=1.5~1.6 GPa), retrograde epidote-blueschist facies stage (t=~450℃, p<1.0 GPa), and post-peak retrograde blueschist-greenschist facies stage (t<400℃, p<0.5 GPa). The p-T pseudosection calculation shows that the peak metamorphic conditions were 520~550℃ and 1.7~1.9 GPa for the eclogites, and 520~620℃ and 1.7~2.3 GPa for the blueschists, similar to the results of traditional geothermobarometer. Previous researchers reported coesites preserved in some eclogites and country rocks, which suggested that partial eclogites and partial country rocks within the southwestern Tianshan metamorphic belt underwent UHP metamorphism, but this conclusion is inconsistent with the results constrained by the eclogites in this study. The possible reasons might be as follows: ① the eclogites were affected by later thermal events, which led to the partial variation of both minerals and whole rock compositions. On the basis of the changed whole-rock compositions, the traditional thermobarometer Grt-Cpx-Phe and phase equilibrium simulations certainly show relatively low pressure results, and ② not all eclogites from the southwestern Tianshan underwent UHP metamorphism, and HP-UHP eclogites may represent the metabasites subducted to different depths.

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    Editor:Zengqian Hou

    Started in:1982

    ISSN 1000-6524

    CN 11-1966/P