Abstract:Zircon U-Pb chronology, rock geochemistry and Sr-Nd isotope have been investigated in this paper to determine the formation time, genesis of rock and formation environment of the granodiorite in Shuangfengshan. The results show that the formation age of Shuangfengshan granodiorite is 334.8±2.1 Ma (MSWD=1.2). The rocks have relatively high SiO₂ (55.42%~65.53%), Na₂O+K₂O (7.42%~8.32%) and Al₂O₃ values (14.84%~17.53%), as well as K₂O/Na₂O ratios (0.16~0.29), which indicates that they are calc-alkaline, quasi-aluminum I-type granite. The rocks are rich in Rb, K, Nd, Zr and Hf, and relatively deficient in Nb, Ta, P, Sm and Ti. Nb/La (0.41~1.01) and Hf/Th (0.80~1.15) ratios are close to the data of typical island arc magmatic rocks. (⁸⁷Sr/⁸⁶Sr)_i(0.706 0~0.709 5) and εNd(t)(-0.22~+0.52) show characteristics of crust-mantle interaction. Combined with regional geological research, the authors hold that Shuangfengshan granodiorite originated from the basaltic lower crust formed in the late Mesoproterozoic on the active continental margin under the underplating of Early Carboniferous basaltic magma, which was the response of the northward subduction of the back-arc basin represented by the Huitongshan-Zhangfangshan ophiolite.

Abstract:Located on the southern margin of the Central Asian giant orogenic belt, the Beishan orogenic belt is one of the key areas for dissecting the accretionary tectonic process of the southern margin of the Central Asian orogenic belt. Researchers have a great controversy about the closing time of the Paleo-Asian Ocean and focus on whether the Devonian ancient Asian Ocean was still subducting or closed. In this study, the authors firstly identified a pluton with typical adakite characteristics in Heishantou area on the southern margin of the Beishan orogenic belt. The geochemical characteristics and zircon U-Pb chronology of the pluton were studied to discuss its genesis and geodynamic significance. The Heishantou pluton is dominated by granodiorite and partially consist of tonalite. The weighted average age of granodiorite LA-ICP-MS zircon U-Pb is 407.7±1.6 Ma. Geochemical data show that the Heishantou pluton belong to peraluminous, calc-alkaline series, with typical adakite characteristics:high silicon (SiO₂=60.85%~67.81%), high alumina (Al₂O₃=15.59%~16.98%), low magnesium (MgO=0.55%~1.53%,Mg^#=0.36~0.46), rich sodium and poor potassium (Na₂O=2.65%~3.54%,K₂O=1.09%~3.16%,Na₂O/K₂O=0.96~2.44), high Sr (Sr=253×10^-6~487×10^-6) low Y and Yb (Y=5.65×10^-6~16.70×10^-6,Yb=0.37×10^-6~0.96×10^-6) compositions, with high Sr/Y ratio (25.75~73.58). Their light rare earth elements (LREE) are enriched, with obvious light and heavy rare earth fractionation. The samples do not have obvious Eu anomaly (0.66~1.31, averaging 0.92). Moreover, trace element composition is characterized by enrichment of LILEs such as Rb, K, Th and U, and depletion of high field strength elements HSFEs such as Nb, Ta, Ti and P. Geochemical characteristics show that these adakites were formed by partial melting of the subducting oceanic crust, and the residual minerals of the crust sources might have been garnet and rutile. Based on this study and regional geological data, the authors hold that the Liuyuan Ocean (Paleo-Asian Ocean) was still in the subduction and collision stage during the Early Devonian and had the characteristics of "scissoring" closure from west to east. The upper limit of the closing time of the Paleozoic ocean basin is Early Carboniferous in the Beishan area.

Abstract:The Beishan area is an important part of the Central Asian Orogenic Belt. The Tanshanzidong basic complex located west of the Beishan Dashantou complex is an important carrier to reveal the late Paleozoic tectonic evolution on the southern margin of the Central Asian Orogenic Belt. This paper reports that the Tanshanzidong basic complex was emplaced with the zircon U-Pb age of 366.0±2.8 Ma. The rocks are characterized by SiO₂ (47.83%~52.25%), K₂O (0.12%~0.45%), Na₂O (2.47%~3.19%), MgO (5.30%~9.22%) and the evolution from tholeiitic series to calc-alkaline series. The rocks are enriched in LREE with positive Eu anomalies, depleted in Nb, Ta, Zr, Ti and enriched in Rb, Ba, Sr, U, K, with the data Nb/La=0.23~0.46, Hf/Th=0.88~3.81, (⁸⁷Sr/⁸⁶Sr)_i (0.704 8~0.704 9) and εNd(t) (+3.72~+4.30), suggesting that they were formed in the arc environment of active continental margin. Based on regional geology, the authors hold that the Tanshanzidong basic complex was the product of partial melting of depleted lithospheric mantle, which was replaced by the subduction fluid during the subduction of the northward subduction of back-arc basin represented by Huitongshan-Zhangfangshan ophiolite. These results provide a direct indication for the vertical growth of the crust caused by the late Devonian crust in the Central Asian Orogenic Belt.

Abstract:Located in the eastern part of the Central Asian Orogenic Belt, the Jalaid Banner of Inner Mongolia is considered to be controlled by the eastern extension of Erlian-Hegenshan fault. It contains the key information of the subduction and extinction process of the Paleo-Asian Ocean. However, the studies of the Ophiolite mélange in this area are relatively weak. In this study, the ophiolite mélange, tonalites-trondhjemite and alkali feldspar granite assemblages related to island arc environment were found in Shabaertu region. Zircon U-Pb dating of the ophiolite mélange shows that their ages are 279.2±3.3 Ma and 278.2±1.7 Ma, respectively, indicating their emplacement in Early Permian. The ultramafic rocks have low SiO₂ content (43.54%~46.38%), low Na₂O and K₂O values, but rich MgO, with Mg^# of 89~94, showing the features of depleted mantle-transitional mantle, which originated from about 70% partial melting of garnet lherzolite. They belong to the supra-subduction zone type (SSZ). The tonalite-trondhjemite is a typical O-type adakite and belongs to the metaluminous and calc-alkaline series, relatively rich in Al₂O₃ and Sr (averaging 600.00×10^-6), but low in Y (averaging 12.50×10^-6) and Yb (averaging 1.18×10^-6), suggesting that they originated from partial melting of the low-K oceanic crust basalts in subduction environment. The alkali feldspar granites are rich in silicon and alkali and low in iron and magnesium. They have high positive εHf(t) values (averaging + 18.9) and are located above the depleted mantle line, with the in-situ zircon Hf isotope one-stage and two-stage model age equal to or less than the crystallization ages of rocks, so they might have been derived from the island arc type juvenile crust. The Shabaetu ophiolite mélange represents the product of intra-oceanic subduction in the early Middle Permian, implying that the Paleo-Asian Ocean was not closed in the early Middle Permian, and the closure time should be at least after the Middle Permian.

Abstract:The Tugurige gold deposit is located in the western part of the Xing'an-Mongolia Orogenic Belt (XMOB). This paper describes the geochronologic and petrological-geochemical data of the intrusive rocks in the Tugurige gold deposit. The LA-ICP-MS U-Pb dating of zircons from syenogranite, granite, hornblendite and diorite in the Tugurige gold deposit yielded weighted mean ²⁰⁶Pb/²³⁸U ages of 264.5±1.4 Ma, 278.7±1.0 Ma, 280.6±1.3 Ma and 288.0±2.6 Ma respectively. The results show that the ages of gold mineralization (268~259 Ma) and syenogranite (276~265 Ma) are the same within error. Geological and geochronological evidence indicates that the syenogranite and gold mineralization have very close genetic relationships. The intrusive rocks in the Tugurige gold deposit are bimodal intrusive rocks, and belong to the high K calc-alkaline series. They are characterized by enrichment of large ion lithophile (Rb, Pb, K, Sr) and light rare earth elements (LREE) and depletion of high field strength elements (Nb, Ta, P, Ti). The intrusive rocks in the Tugurige gold deposit have some geochemical characteristics of the intrusive rocks in the subduction zone. This indicates that the source of these intrusive rocks was probably altered or affected by subduction events, but can not constrain their geological background. Combined with geological data available, the authors hold that the intrusions and gold mineralization in the Tugurige area were related to post-collisional extension of the Central Asian Orogenic Belt (CAOB).

Abstract:The subduction of the Paleo-Pacific Plate played an important role in the regional tectonic evolution of the eastern margin of the Eurasian continent, but the timing of this event remains ambiguous. To address this issue, this paper reports zircon U-Pb ages, zircon Hf isotopic compositions and petrogeochemical data of whole-rocks for the newly-found hornblende gabbro in Aohua Village, central Jilin Province. Zircon U-Pb dating shows that the hornblende gabbro was formed in Early Jurassic (180.3±2.3 Ma), and has high and uniform εHf(t) values (9.6~11.3). Petrogeochemical analyses show that the samples are characterized by low Si and Al, and high Fe, Mg, and Ca, enrichment of light rare earth elements and large-ion lithophile elements (e.g., Rb, Ba, U, K, and Sr), and depletion of heavy rare earth elements and high-field-strength elements (e.g., Nb, Ta, and Ti), and have weak negative Eu anomalies (δEu=0.67~0.98). They were derived from a depleted lithospheric mantle source that had previously been metasomatized by slab-derived fluids, with unapparent effects of fractional crystallization, crustal contamination and cumulation in the formation process. Combined with rock associations and spatial distri- bution of Early Mesozoic igneous rocks in the eastern part of Northeast China, the authors hold that the subduction of the Paleo-Pacific Plate beneath the Eurasian continent started in Early Jurassic, and the hornblende gabbro was formed in the back-arc setting which might have been closely related to the subduction of the Paleo-Pacific Plate.

Abstract:The large-scale tectono-magmatism and mineralization during Mesozoic in eastern North China Craton resulted from the subduction of paleo-Pacific plate, although the starting time of subduction is still in dispute. In this study, the granitoids from Yaowangmiao-Mopan Mountain pluton in Xingcheng area, western Liaoning Province, were taken for systematic researches, including petrology, zircon U-Pb dating, geochemistry and zircon Hf isotopic analysis. Magmatic zircons yielded weighted mean ages of 193 Ma and 186 Ma, so the Yaowangmiao-Mopan Mountain pluton was emplaced during Early Jurassic. The granitic rocks are composed of quartz monzonite, granodiorite, monzogranite and syenogranite. All of these rocks have high total alkalis content and quasi-aluminous to weakly peraluminous characteristics, belonging to the high-K calc-alkaline series with geochemical characteristics similar to those of I-type granite. These rocks are enriched in LREE and K, Pb and depleted in Nb, Ta, Ti and P. The magmatic zircons of the Early Jurassic granitoids have negative εHf(t) (-12.94~-7.39) and ancient t_DM2 values (2.05~1.69 Ga) which indicates that the primary magma was derived from the partial melting of ancient continental crust probably with the mixture of mantle source materials. The Early Jurassic granitic rocks in Xingcheng area of western Liaoning Province have rock assemblages and geochemical characteristics similar to the granitoids formed under the active continental margin related to the subduction of paleo-Pacific plate. The results in this study and regional geological data all indicate that the subduction of paleo-Pacific plate began during Late Triassic-Early Jurassic, and the Early Jurassic granitic magmatism resulted from the response to the subduction of paleo-Pacific plate in eastern North China Craton.

Abstract:Located at the junction of the southeastern margin of the North China Craton and the northeastern section of the Dabie-Sulu orogenic belt, the Jiaodong area is an ideal place for studying the transformation of regional tectonic mechanism and craton destruction. In this paper, the authors chose the Late Mesozoic granite as the research object, and carried out detailed petrographic, petrogeochemical, zircon LA-ICP-MS U-Pb geochronological and Sr-Nd isotope studies, focusing on the origin and evolution history of magma and geodynamic mechanism of regional diagenesis and mineralization. The results show that the emplacement ages of Jurassic continental crust remelted Linglong-type granite, Cretaceous crust-mantle mixed Guojialing-type granite and Weideshan-type granite are 163.2~157.9 Ma, 132.9~130.0 Ma, and 121.3~116.7 Ma, respectively, and the emplacement ages of Cretaceous Laoshan-type granite and vein rock are 125.0 Ma and 120.7 Ma, respectively, which are basically in line with the previous age test data. From Jurassic to Early Cretaceous, the chemical composition of granites evolved from high-potassium calc-alkaline series to shoshonite series, i.e., from peraluminous to metaluminous, trace element content evolved from high Ba-Sr to low Ba-Sr and from high Sr, low Y to low Sr and high Y, REE varied from no or weak positive Eu anomaly to significant negative Eu anomaly, and the type of granites varied from S-type to I-type and A-type. It shows the evolution trend from EM2 enriched mantle to EM1 enriched mantle, from enrichment to depletion or from lithosphere to asthenosphere. The Jiaodong area in the Late Mesozoic experienced the transformation from North China-Yangtze tectonic system to Eurasian-Pacific tectonic system and from compression mechanism to extension mechanism. The strong thermal-uplift extension structure in Early Cretaceous provided favorable conditions for large-scale gold mineralization.

Abstract:The Liaoshang gold deposit is a newly discovered superlarge gold deposit on the northeast margin of Jiaolai Basin, which is different from "Jiaojia-type" and "Linglong-type" gold deposits by unique gold bearing minerals of pyrite and dolomite. The isotopic analysis of C, O for Au-bearing dolomite and S, Pb for Au-bearing pyrite from this deposit was carried out in order to identify the source of ore-forming materials and fluids for this new type gold deposit. The results show that the δ¹³C_V-PDB and the δ¹⁸O_V-SMOW values of dolomite range from -4.60‰ to -3.60‰ and 9.6‰ to 10.6‰, respectively. The δ³⁴S values of Au-bearing pyrite vary from +7.2‰ to +9.4‰ with an average of +8.2‰. The results of Pb isotope from Au-bearing pyrite vary from 17.027 to 17.576, 15.435 to 15.503, and 37.706 to 38.205 for ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb ratios, respectively. Combined with the tectono-magmatic evolution in the Jiaolai Basin, the authors hold that the ore-bearing C-H-O fluids of the Liaoshang gold deposit mainly originated from the mantle. Furthermore, the meteoric water and crustal ore-forming materials were involved during the ascending process of ore-forming fluids, resulting in the characteristics of crust-mantle mixing. In conclusion, the genetic type of Liaoshang gold deposit should be the pyrite-carbonate vein type low temperature hydrothermal gold deposit.

Abstract:This paper reports a new type of high temperature REE-rich barytocalcite, which occurs in REE-enriched alkaline carbonate veins in Songxian County, Henan Province, East Qinling. The molecular formula of the studied barytocalcites is Ba_1.04Ca_0.81Sr_0.14(CO₃)₂ (Sr-barytocalcite) based on Stoichiometric calculation using the major element compositions. LA-ICP-MS analyses show high concentrations of Na, K, Fe, Mn, Pb, Y and REEs in the barytocalcite. The total REE concentrations of the barytocalcites are up to 4 080×10^-6, which generally show LREE-enriched and HREE-depleted patterns. Contrasting to sedimentary barytocalcite formed in low temperature, backscattered electron images suggest that the studied barytocalcites have two types of high-temperature textures intergrowing with aegirine augite or with quartz + calcite + apatite. The intergrowth of orthomorphic barytocalcite with primary calcite suggests that they were formed in the early stage of alkaline melt evolution, likely crystallized in a carbonate and silicate immiscible environment. The later stage calcites were found in barytocalcites and aegirine augites in patch shape, implying a carbonate metasomatic stage. The assemblage of aegirine augite + K-feldspar + albite + pyroxene + apatite +calcite + quartz + barytocalcite is consistent with that in carbonatites. The features of high Ba, Sr and REE content in the studied carbonatites are also of high similarity to well-known large-scale REE-rich carbonatite ore deposits (e.g., the Maoniuping REE deposit). Together with detailed geological features of the alkaline carbonate veins, the results obtained by the authors could provide a general guideline for exploration of carbonatite REE deposits in the East Qinling region.

Abstract:The Dewulu pluton is located between Xiahe-Hezuo fault and Lishishan-Weidangshan fault. The hose rock is predominantly composed of granodiorite with subordinate quartz diorite and quartz monzodiorite, and contains a large number of microgranular mafic enclaves (MMEs). Some Cu-Au deposits occur within the pluton and have been studied by many researchers; nevertheless, there are few researches on the pluton. LA-ICP-MS zircon U-Pb dating on the granodiorite of the Dewulu pluton yielded an age of 225.9±1.3 Ma, suggesting that the pluton was formed in the early period of late Triassic, and might have been related to the continental collision between the Yangtze and North China plates. Petrogeochemical studies show that host rocks are characterized by high K₂O and low Y and MgO, while the MMEs by low K₂O and high Y and MgO. Both host rocks and MMEs have similar features in trace element spider diagram and REE distribution pattern and obvious linear relationship on Al₂O₃/MgO-SiO₂/MgO diagram. These phenomena indicate that material exchange took place in these rocks, and quartz diorite, quartz monzodiorite and granodiorite were generated by the mixing of mafic and felsic magmas resulting from the strong crust-mantle interaction occurring in the extensional environment after the collision of the Yangtze and North China plates. MMEs may be the remnant of the parental mafic magma, and their geochemical characteristics show that they might have been derived from the mantle which was enriched in Au, Cu and other ore-forming elements. The Cu and Au enriched fluid was produced during the evolution of the mixed magma, and precipitated in the Dewulu pluton to form the hydrothermal Cu-Au deposits.

Abstract:Emeishan basalts, widely distributed in Sichuan, Yunnan and Guizhou in southwestern China, are the earliest internationally recognized large igneous provinces in China and have been favored by a large number of experts both in China and abroad. Many consensuses have been reached on the basalt in the western part of the Emeishan large igneous province (ELIP), but there are still several controversies in such aspects as the rock associations, the time limit of volcanic activities and the genesis of rocks. With the basalt of Pu'an in western Guizhou, eastern part of ELIP as the study object and through the analysis of typical basalt profiles, the authors detected that the rock types in this area are eruptive facies of volcanic breccia in the first cycle, flooding facies of basalt in the second cycle and volcanic sedimentary facies of tuff in the third cycle from bottom to top. Zircon LA-ICP-MS U-Pb dating from the tuff which is located at the top of the basalt defined the upper time limit of volcanic activity in the east of the ELIP to 250 Ma. The major and trace elements indicate that the basalts in this area are mainly high-Ti and alkaline basalts. The characteristics of Rb-Sr depletion and Ba-Hf enrichment are basically consistent with the geochemical characteristics of basalts in Guizhou, high Ti basalts in the west of ELIP, and OIB. Trace elements show that the origin of the basalt is metasomatic garnet mantle peridotite, and the melt generated by partial melting when rising from the deep mantle plume to the stable area of garnet peridotite was mixed with the continental lithospheric mantle enriched with metasomatic fluids. Crystallization differentiation was significant while the crustal mixing degree was weak during the ascent and migration of magma. The results show that the basalt in the eastern ELIP was formed in the environment of greater depth, low partial melting and high pressure at the edge of the mantle plume.

Abstract:Abundant Neoproterozoic magmatic rocks were emplaced in western Yangtze Block, which are important for reconstructing the Rodinia supercontinent. In this paper, new petrologic, lithogeochemical and geochronological studies of the Eshan granodiorites and porphyritic biotite monzogranites were conducted to explore their origin and geodynamic implications. The porphyritic biotite monzogranites were emplaced at 826.6±2.5 Ma, while the granodiorites have younger crystallization age of 818.3±2.8 Ma. Relative to the porphyritic biotite monzogranites, the granodiorites exhibit lower SiO₂ but higher Al₂O₃, MgO, Fe₂O₃, TiO₂ and P₂O₅ values. In chondrite-normalized REE patterns and trace element spider diagram, both lithologies are enriched in LREEs; compared with HREEs, they have negative Eu anomalies and are depleted in HFSEs relative to LILEs. The porphyritic biotite monzogranites have enriched Nd isotopic compositions, consistent with those of the granodiorites. The geochemical data indicate that the porphyritic biotite monzogranites are likely to have been derived by partial melting of meta-igneous rocks, leaving a granulite source at ca. 826 Ma and subsequent partial melting of the granulite at ca. 818 Ma, thus producing the Eshan granodiorites with A-type affinities. Combined with data available, the results obtained by the authors reveal that the western Yangtze Block was an active continental margin and the South China Block occupied an external location rather than an internal location within the Neoproterozoic Rodinia.

Abstract:The intermediate-acid intrusions in northern Anhui Province of Xu-Su arc were formed by multi-stage magma, and a series of skarn (Fe)-Au-Cu-(Mo) and Fe-Cu deposits related to these intermediate-acid intrusive rocks have been developed. In this paper, the authors studied the zircon U-Pb age of diorite porphyrite which hosts the Wangchang skarn-type iron deposit and Re-Os isotopic age of the molybdenite in the largest skarn-type gold deposit (Yangqiaozi Au-Cu deposit) in this area. The LA-ICP-MS U-Pb weighted age of the Wangchang diorite porphyrite zircon is 132.1±1.9 Ma, and the Re-Os isochron age of the molybdenite in the Yangqiaozi deposit is 130.0±3.2 Ma. The authors systematically summarized the diagenetic age, mineralization type and metallogenic regularity in this area. It is considered that the magmatic rocks in this area can be divided into four stages, and the deposits can be divided into four types. Specifically, the first stage magmatic rocks are early Neoproterozoic mafic intrusive rocks (diabase), which are related to the diamond deposits. The second stage magmatic rocks are intermediate acid intrusive rocks formed in the early Jurassic. The third stage magmatic rocks are the Early Cretaceous intermediate-acid intrusive rocks, which are related to skarn type Fe deposits and skarn type (Fe)-Au-Cu-(Mo) deposits. The fourth stage is late Early Cretaceous acid intrusive rocks. The magmaic Cu-Ni deposits related to mafic intrusive rocks were discovered, but there has been no chronological research reported yet. The Fe and Au-Cu mineralization related to intermediate acid intrusive rocks have been widely developed, but just a few Cu-Ni and diamond mineralizations related to mafic intrusive rocks have been discovered in the in northern Anhui Province of Xu-Su arc. The magmatic rocks in the study area were formed in the extensional structural environment of the North China Craton, but were controlled by different geological events. The large-scale diagenesis and mineralization ages in the area are concentrated in the Early Cretaceous, which was probably related to the destruction of the lithosphere of the North China Craton. The chronological and geochemical data of magmatic rocks and mineralization indicate that there may be a hydrothermal gold polymetallic deposit similar to the Jiaodong area in the deep Xu-Su arc area, which provides a reference for future prospecting in this area.

Abstract:The Daping Au deposit is one of the most important large-sized gold deposits in the south of the Ailao Mountain-Honghe River ductile shear zone. Due to the disputes on its mineralization timing and tectonic setting, it's difficult to establish the metallogenic model as well as further explore and exploit gold deposits in this belt. In this paper, LA-ICP-MS was used to study the U-Pb geochronology of hydrothermal zircon from Au-bearing quartz veins and magmatic zircon from diorite and granodiorite vein in the Daping Au deposit. The result shows that the age of hydrothermal zircon is 760±10 Ma, suggesting that there was a Neoproterozoic mineralization event for the Daping gold deposit. The magmatic zircons from the diorite and granodiorite vein yielded ages of 773±9 Ma and 766±9 Ma, respectively. These results coincide with the breakup of the zircons from the diorite and granodiorite veins. Therefore, combined with their consistent ages within the error range, the authors hold that the Neoproterozoic gold mineralization event might have been Rodinia supercontinent and the Jinning-Chengjiang large-scaled volcanic-magmatic event in the Ailao Mountain area. The hydrothermal zircons have similar Hf isotopic composition to those of related intrusions of diorite and granodiorite. Although the Eocene-Oligocene was thought to be a main mineralization period for the Daping gold deposit in previous literature, the authors consider that the Daping gold deposit probably resulted from superimposed mineralization from the Neoproterozoic and Cenozoic magmatic-tectonic-hydrothermal events, as shown by the determination of the Neoproterozoic mineralization event in this study.

Abstract:The Dahongshan iron-copper deposit is hosted in metavolcanic to metasedimentary rocks of the Paleoproterozoic Dahongshan Group. Up to now, the genesis and tectonic environment of these ore-bearing rocks have been still controversial, which seriously restricts the understanding of the metallogenic mechanism and process. In order to identify the original rock types and diagenetic tectonic environment of these host rocks, the authors systematically studied major, trace and rare earth element compositions of main ore-bearing metamorphic rock series, including the meta-sodic volcanic rocks, mica schists and marbles, as well as the gabbro-diabase rocks. According to the results obtained, the ore-bearing rocks are characterized by poor K, Ti and rich Na, the meta sodic volcanic rocks are relatively depleted in Ba, Sr and Ti, weakly depleted in Zr, Hf and Nb, and are enriched in Th, Nd, Sm and La; their total content of rare earth elements are generally low, with LREEs relative enrichment(LREE/HREE=1.84~9.43), significant Eu positive anomalies(δEu=0.91~3.59, mean=1.62), and no obvious Ce anomalies. These characteristics are similar to those of rocks from jet deposition or high temperature submarine volcanism in the modern mid-ocean ridge or intracontinental rift. According to the comprehensive study, the protolith of mica schist may have been a calcareous mudstone, while the protoliths of meta-sodic lavas and meta-sodic tuffs are volcanic rocks which erupted in the bathyal environment, with high Na content. Meta-sodic volcanic rocks and gabbro-diabase rocks show similar anorogenic features to the magmatic rocks in the same period of Kangdian area, indicating that they are all products of magmatic activities in the same continental rift environment which may represent the Columbia supercontinent cracking process on the western margin of Yangtze block. The continental breakup generated some channels for the migration of mantle-derived magma, and provided a good material basis for the formation of the iron copper polymetallic metallogenic belt in Kangdian area.

Abstract:The main types of beryllium deposits in Yunnan Province include pegmatite type, magmatic-hydrothermal vein type, altered granite type and greisen type. The pegmatite type, magmatic-hydrothermal vein type and altered granite type are the most important types of deposits, which account for more than 95% of the total resources of beryllium in Yunnan Province. These deposits are closely related to the high-differentiation granite of crust source and mostly distributed in Gejiu and Dulong regions in southeast Yunnan as well as in Gaoligong Mountain and Shangri-la regions in western Yunnan. The deposits were formed in the late Cretaceous in southeast Yunnan and Oligocene in west Yunnan. Beryllium mineralization in southeast Yunnan resulted from a response to lithospheric extension in western South China in late Yanshanian period. The geodynamic background of beryllium minerali- zation in western Yunnan seems to have been the collision orogeny between the Indian and Eurasian continents. In this paper, the authors propose three prospecting areas, namely Gongshan-Tengchong-Yingjiang, Longling and Maguan-Malipo prospective areas. In the three prospective areas, researchers should focus on finding pegmatite-type beryllium deposits.