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| 1 | Geochronology and petrogenesis of granitic rocks in Gangdese batholith, southern Tibet显示文摘Based on petrological and geochemical characteristics such as rock assemblage, petrogeochemistry, Sr-Nd isotope, zircon U-Pb age, and Hf isotope, we studied geochronological framework, magma types, source characters, and petrogenesis of different stages of magmatism of the granitic rocks from the Gangdese batholith in southern Tibet. The magmatic activities of the Gangdese batholith can be divided into three stages. The Mesozoic magmatism, induced by northern subduction of Neotethyan slab, was continuously developed, with two peak periods of Late Jurassic and Early Cretaceous. The Paleocene-Eocene magmatism was the most intensive, and resulted from a complex progress of Neotethyan oceanic slab, including subduction, rollback, and subsequent breakoff. And the Oligocene-Miocene magmatism was attributed to the convective removal of thickened lithosphere in an east-west extension setting after India-Asia collision. Isotopically, zircons from these granitic rocks are characterized by positive εHf(t) values, suggesting that the magmatic source of the Gangdese batholith might be an arc terrane, which was accreted to the southern margin of Asia during Late Paleozoic. Therefore, the chronological framework and Hf isotopic characteristics of the Gangdese batholith are distinct from the granitic rocks in adjacent areas, which can be served as a powerful tracer in studying source-to-sink relation of sediments during the uplift and erosion of Tibetan Plateau. | JI WeiQiang WU FuYuan LIU ChuanZhou CHUNG SunLin | 2009 | Science China Earth Sciences2009，52，9： | 89 |
| 2 | Strongly peraluminous granites of Mesozoic in Eastern Nanling Range, southern China: Petrogenesis and implications for tectonics显示文摘The strongly peraluminous granites (SPGs) of Eastern Nanling Range (ENR) are a characteristic of all bearing highly aluminous minerals, such as muscovite±Al-rich biotite±tourmaline±garnet, and lack of cordierite. In respect of petrography, geochemistry, Nd isotope, and single grain zircon U-Pb dating, the representative granite bodies of them are studied. The research shows that these granites were emplaced in two stages, namely 228-225 Ma BP and J2-3 159-156 Ma BP, belonging to Indosinian and early Yanshanian periods, respectively, and they have low εNd(t) values (-10.6--11.1), high A/CNK, Rb/Sr ratios and tDM values (1887-1817 Ma), and REE's tetrad effect (TE1, 3=1.13-1.34). In comparison with related geology, petrology and chronology of granites in adjacent regions, it is suggested that Indosinian SPGs of ENR formed in the circumstance of post-collisional extension 20 Ma after the major collision of Indosinian Movement (258-243 Ma BP) in Indo-China Peninsula, and early Yanshanian SPGs formed in the background of back-arc extension setting controlled by paleo-Pacific tectonic domain, and J1, the interval of two stages, is the interim from Tethyan to Pacific tectonic domains in South China. These SPGs have similar geological and geochemical characteristics, because they all crystallized from the magma of partial melting of early Proterozoic metasedimentary rocks when the thickened crust (≤50 km) became thinning, decompression, and transmitting of water. | SUN Tao, ZHOU Xinmin, CHEN Peirong, LI Huimin, ZHOU Hongying, WANG Zhicheng & SHEN Weizhou Department of Earth Sciences, Nanjing University, Nanjing 210093, China Tianjin Institute of Geology and Mineral Resources, China Geological Survey, Tianjin 300170, China | 2005 | Science China Earth Sciences2005，48，2： | 78 |
| 3 | Geochemical and Pb-Sr-Nd isotopic compositions of Indosinian granitoids from the Bikou block,northwest of the Yangtze plate:Constraints on petrogenesis,nature of deep crust and geodynamics显示文摘This paper reports geochemical and Pb-Sr-Nd isotopic compositions of the Indosinian Yangba (215 Ma),Nanyili (225 Ma) and Mopi granitoids from the Bikou block of the northwestern margin of the Yangtze plate. These granitoids are enriched in Al (Al2O3:14.56%―16.48%) and Sr (352 μg/g―1047 μg/g),and depleted in Y (<16 μg/g) and HREE (e.g. Yb<1.61 μg/g),resulting in high Sr/Y (36.3―150) and (La/Yb)N (7.8―36.3) ratios and strongly fractionationed REE patterns. The Indosinian granotoids show initial Sr isotopic ratios (ISr) from 0.70419 to 70752,εNd(t) values from-3.1 to -8.5,and initial Pb isotopic ratios 206Pb/204Pb=17.891-18.250,207Pb/204Pb=15.494-15.575,and 208Pb/204Pb=37.788-38.335. Their geochemi-cal signatures indicate that the granitoids are adakitic. However,they are distinct from some adakites,generated by partial melting of subducted oceanic slab and/or underplated basaltic lower crust,be-cause they have high K (K2O: 1.49%―3.84%) and evolved Nd isotopic compositions,with older Nd iso-topic model ages (TDM=1.06―1.83 Ga). Geochemical and Sr-Nd isotopic compositions suggest that the magmas of the Insoninian adakitic rocks in the Bikou block were derived from partial melting of thick-ened basaltic lower crust. Combined with regional analyses,a lithospheric delamination model after collision between the North China and South China plates can account for the Indosinian adakitic magma generation. On the other hand,based on the Pb-Sr-Nd isotopic probing to the magma sources of the adakitic rocks,it is suggested that there is an unexposed continent-type basement under the exposed Bikou Group volcanic rocks. This can constrain on the Bikou Group volcanic rocks not to be MORB-or OIB-type. | ZHANG HongFei XIAO Long ZHANG Li YUAN HongLin JIN LanLan | 2007 | Science China Earth Sciences2007，50，7： | 38 |
| 4 | Petrogenesis of Shangyu gabbro-diorites in western Shandong:Geochronological and geochemical evidence显示文摘Chronology and geochemistry of the Shangyu gabbro-diorite in western Shandong were studied to understand their petrogenesis and the nature of the Mesozoic lithospheric mantle. The Shangyu intru-sion is mainly composed of a suite of gabbro-diorite. Zircons from the intrusion display eu-hedral-subhedral in shape and have high Th/U ratios (1.23―2.87), implying their magmatic origin. LA-ICP-MS zircon U-Pb dating results for two samples indicate that they were formed in the Early Cre-taceous, yielding weighted mean 206Pb/238U ages of 129±1Ma and 134±2Ma, respectively. Except for early cumulate such as sample QT-19, their SiO2 and MgO contents range from 50.12% to 56.37% and from 3.52% to 6.37%, respectively. Moreover, the gabbro-diorites are characterized by high Mg# (0.54―0.63), enrichment in Na (Na2O/K2O ratios more than 1), Cr (73×10-6―217×10-6) and Ni (34×10-6―241×10-6), and intensive enrichments in light rare earth elements (LREEs) and large ion lithophile elements (LILEs) and depletion in high field strength elements (HFSEs). Their initial 87Sr/86Sr ratios and ε Nd(t) values range from 0.70962 to 0.71081 and from-16.60 to-13.04, respectively. Taken together with the Early Creta-ceous high-Mg diorites and the mantle xenoliths from the Tietonggou and Jinling as well as basalts from the Fangcheng and Feixian, it is suggested that the primary magma for the Shangyu gab-bro-diorites should be derived from the enriched lithospheric mantle intensively modified by conti-nental crust. The Sr-Nd-Pb isotopic compositions for the Early Cretaceous high-Mg diorites in western Shandong display a trend of spatial variations, i.e., initial 87Sr/86Sr, 207Pb/204Pb and 208Pb/204Pb ratios de-creasing and ε Nd(t) values increasing from southeast to northwest in western Shandong, which is con-sistent with the tectonic model that the Yangtze Craton subducted beneath the North China Craton oriented in north-west direction in the Early Mesozoic. | YANG ChengHai XU WenLiang YANG DeBin WANG Wei WANG WeiDe LIU JinMin | 2008 | Science China Earth Sciences2008，51，4： | 24 |
| 5 | Petrogenesis of Indosinian volcanic rocks in Songpan-Garze fold belt of the northeastern Tibetan Plateau:New evidence for lithospheric delamination显示文摘In the Songpan-Garze fold belt of the northeastern Tibetan Plateau, an Indosinian lithospheric delamination model has been proposed, based on previous investigation of widespread granitoids. However, this model lacks comparable information from volcanism in the area. During the Indosinian delamination in the Songpan-Garze fold belt, whether partial melting of litho- spheric mantle taken place is debated. This paper reports U-Pb zircon LA-ICP-MS ages, geochemical and Sr-Nd-Hf isotopic compositions from the Aba and Wasai calc-alkaline volcanic rocks in the central Songpan-Garze fold belt. Obtained magma crystallization ages are 210±3 Ma for the Aba andesite and 205±1 Ma for the Wasai andesite. These are consistent with magma crystallization ages of the late Indosinian granitoids in the Songpan-Garze fold belt that formed in a post-collisional tectonic setting. The Aba and Wasai andesites have distinct geochemical singnatures. The former has higher Al2O3, K2O, Rb but lower Na2O, Ba and Sr contents, suggesting differences in their magmatic evolution. The Aba andesites have ISr values of 0.7070-0.7076 and εNd(t) values of -3.9 to -5.3, and the Wasai andesites have ISr values of 0.7075-0.7077 and εNd(t) values of -3.6 to -3.9. Zircons show εHf(t) values of -3.7 to 0.3 for the Aba andesites and -2.7 to 5.5 for the Wasai andesites. Geochemical and Sr-Nd-Hf isotopic compositions indicate that fractional crystallization and crustal assimilation processes are not key roles for their magma evolution, implying that their chemical compositions are those of primary melts. We suggest that the magma of the Aba andesites originated predominantly from a crustal source, with a minor mantle-derived component. The source region of the magma was likely at the crust-mantle boundary. The magma of the Wasai andesites resulted from partial melting of lithospheric mantle, which was probably metasomatized by fluids so that it was amphibole bearing. The petrogenesis of the Aba and Wasai andesites provides an additional evidence for the lithospheric delamination in the the Songpan-Garze fold belt, indicating that this process invoked mantle asthenosphere upwelling and caused the partial melting of remaining lithospheric mantle. | CAI HongMing1,2, ZHANG HongFei1,2, XU WangChun1,2, SHI ZhangLiang1,2 & YUAN HongLin3 1 State Key Laboratory of Geological Processes and Mineral Resources, Wuhan 430074, China 2 Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China 3 State Key Laboratory of Continental Dynamics, Northwest University, Xi’an 710069, China | 2010 | Science China Earth Sciences2010，53，9： | 14 |
| 6 | Deep xenoliths in alkalic porphyry,liuhe,Yunnan,and implications to petrogenesis of alkalic porphyry and associated mineralizations显示文摘Na-rich microlite-glass is first discovered in deep-source xenoliths in alkali-rich porphyry, Liuhe village, Heqing County, Yunnan Province. It is shown that the ultramafic xenoliths originated from partial melting of primary mantle and the glass resulted from metasomatism between the xenoliths and mantle fluid derived from mantle degassing. Mantle metasomatism not only resulted in the enrichment of alkaline, large-ion elements, ore metals and volatiles but also created a favorable condition for the generation of alkaline magmas. The mantle xenoliths and their characteristics of mantle metasomatism provide important evidence for a better understanding of the petrogenesis and mineralization of the Cenozoic alkali-rich porphyry in western Yunnan. | 刘显凡 战新志 高振敏 刘家军 李朝阳 苏文超 | 1999 | Science China Earth Sciences1999，42，6： | 10 |
| 7 | A petrogenetic study of the garnet pyroxenite enclaves in spinel peridotite, North Dabieshan, China显示文摘Recently, garnet pyroxenite enclaves within peridotites occurring near Raobazhai, Huoshan County, have been discovered. The garnet pyroxenite is small pods, decimeters in size, enclosed within intensively serpentinized peridotites. Major mineral components comprise: garnet (Prpas-as), sodium augite (Jd 10-25) with a small amount of ilmenite. There are two stages of retro-metamorphism: the retrogressive granulite facies mineral assemblage is superimposed by that of amphibolite facies. The host rocks of the garnet pyroxenite are spinel peridotites, including spinel harzburgite and Iherzolite. Due to intensive serpentinitization, only 5%-40% of the relic olivine (Fo92-93) are preserved. The orthopyroxenes are Mg-rich (En87-93) with bending of cleavages and granulation at their margins showing intracrystalline plasticity. On the basis of garnet-clinopyroxene Fe-Mg exchange equilibrium geothermometry proposed by Ellis & Green (1979) and Krogh (1988) KD= 4.06 - 5.28; T= 793-919℃, P= 1.5 GPa are estimated | 游振东 钟增球 索书田 郑曙 | 2000 | Science China Earth Sciences2000，43，S1： | 5 |
| 8 | Geochemistry and zircon U-Pb geochronology of the rhyolitic tuff on Port Island, Hong Kong: Implications for early Cretaceous tectonic setting显示文摘Early Cretaceous rhyolitic tuffs,widely distributed on Port Island,provide insights into the volcanism and tectonic setting of Hong Kong.In this paper we present petrological,geochronological and geochemical data of the rhyolitic tuff to constrain the diagenesis age and petrogenesis of the rocks,tectonic setting and early Cretaceous volcanism of Hong Kong.The first geochronological data show that the zircons in the volcanic rocks have U-Pb age of 141.1-139.5 Ma,which reveals that the rhyolitic tuff on Port Island was formed in the early Cretaceous(K_1).Geochemically,these acid rocks,which are enriched in large ion lithophile elements(LILEs) and light rare earth elements(LREEs),and depleted in high field strength elements(HFSEs),belong to the high K calc-alkaline to shoshonite series with strongly-peraluminous characteristic.The geochemical analyses suggest that the volcanic rocks were derived from deep melting in the continental crust caused by basaltic magma underplating.Based on the geochemical analysis and previous studies,we concluded that the rhyolitic tuffs on Port Island were formed in a backarc extension setting in response to the subduction of the Paleo-Pacific Plate beneath the Eurasian Plate. | Longlong Zhao Lulin Wang Mingzhong Tian Fadong Wu | 2017 | Geoscience Frontiers2017，8，3： | 4 |
| 9 | Geochronology and Geochemistry of the Granites from the Longtoushan Hydrothermal Gold Deposit in the Dayaoshan Area,Guangxi:Implication for Petrogenesis and Mineralization显示文摘The gold mineralization in the Longtoushan hydrothermal gold deposit is concentrated within the contact zone of the granitic complex. Whole rock geochemistry and in-situ U-Pb and Hf isotopic data were used to constrain the genesis and age of the granites and related Cu-Au mineralization in the Longtoushan Deposit. The granites mainly consist of the granite porphyry, rhyolite porphyry, porphyritic granite and quartz porphyry. LA-ICP-MS U-Pb dating of zircons from the granite porphyry, rhyolite porphyry and quartz porphyry indicates that they intruded from ca. 94 to 97 Ma. These intrusions exhibit similar trace element characteristics, i.e., right-dipping REE patterns, depletion of Ba, Sr, P and Ti, and enrichment of Th, U, Nd, Zr and Hf. The εHf(t) values of zircons from the granite porphyry, rhyolite porphyry and quartz porphyry range from-26.81 to-8.19,-8.12 to-5.33, and-8.99 to-5.83, respectively, suggesting that they were mainly derived from the partial melting of the Proterozoic crust. The Cu-Au mineralization is mainly related to the rhyolite porphyry and porphyritic granite, respectively. The Longtoushan granites were most likely formed in a post-collisional extensional environment, and the deposit is a part of the Late Yanshanian magmatism related mineralization in the Dayaoshan area and its adjacent areas. | Lihua Qian Jianqing Lai Lifang Hu Rong Cao Shilong Tao Bei You | 2019 | Journal of Earth Science2019，30，2： | 4 |
| 10 | Two Types of Granites in the Western Yangtze Block and Their Implications for Regional Tectonic Evolution: Constraints from Geochemistry and Isotopic Data显示文摘In the western Yangtze Block, widespread Mesoproterozoic to Neoproterozoic rocks are the key to understanding the Precambrian tectonic-magmatic evolution of the region. However, their petrogenesis and tectonic setting are still controversial. In this paper, zircon U-Pb ages, Sm-Nd isotopic and whole-rock geochemical data are reported from selected fresh samples in the southern Dechang county, southwestern China, in order to constrain their emplacement age and magma source, as well as their petrogenesis and tectonic setting. They are mainly composed of biotite monzogranite, monzonitic granite, biotite granodiorites, and quartz diorite. Two ages of 1055 ± 43 Ma and 837.6 ± 3.8 Ma were obtained through zircon U-Pb dating by LA-ICP-MS and LA-MC-ICP-MS, respectively. According to their major element compositions, the Grenville-age granites are peraluminous calc-alkaline series calcic S-type granite. In contrast, the mid-Neoproterozoic granites are metaluminous calc-alkaline series alkalic I-type granite. Furthermore, the S-type granites are enriched in LREEs relative to HREEs with(La/Yb)_N ratios of 3.85–18.56 and underwent major fractionation with strongly negative Eu anomalies(Eu/Eu~* = 0.38–0.66). In the MORB-normalized trace element variation diagram, all the samples are enriched in Ce and large ion lithophile elements such as Rb, Th, and K, and depleted in high field strength elements such as Nb, and Ti, with negative Sr and Ti anomalies. The I-type granites are enriched in LREEs with slight negative Eu anomalies(Eu/Eu~* = 0.83–0.93). They are characterized by the enrichment of highly incompatible elements(such as K, Rb, Ba, Th) and LREEs, relative to MORB. Neodymium isotopic data show that the S-type granites display ^(143)Nd/(^(144) Nd) values of 0.51241–0.51256, and have ε_(Nd)(t = 1055 Ma) values of(-3.29) to(-3.81). Calculated t_(DM) ages yield values from 1.87 to 1.91 Ga with the t_(DM).2 stg ages of 1.86 to 1.9 Ga. The I-type granites have ^(143)Nd/(^(144) Nd) ratios between 0.51192 and 0.51195, corresponding to initial ε_(Nd)(t = 837 Ma) values of 1.22 to 5.63. Calculated t_(DM) ages yield values from 1.0 to 1.38 Ga and the t_(DM).2 stg ages yield values from 0.99 to 1.06 Ga. The S-type granites are distinguished as syn-collision granite, whereas the I-type granites were formed as arc magmas according to the Rb-(Yb+Ta) and R_1-R_2 tectonic discrimination diagrams. To conclude, there are two types of spatially associated granite, the Mesoproterozoic S-type granite which were derived from remelting of upper crustal mudstone and/or clastics and resulted from the convergence of two continental plates, and the mid-Neoproterozoic I-type granite which formed in continental arc and resulted from mantle-derived magma mixed crust material, in the western Yangtze Block. Furthermore, we suggest that collision between the Yangtze and Cathaysia blocks occurred at about 1055 Ma, and caused the Stype granite. The I-type granite related to the subduction of oceanic lithosphere eastward underneath the Yangtze Block in the mid-Neoproterozoic. | MABI Awei YANG Zhengxi ZHANG Mingchun WEN Dengkui LI Yanlong LIU Xuyang | 2018 | Acta Geologica Sinica(English Edition)2018，92，1： | 4 |
| 11 | Geochemistry and Petrogenesis of Late Cretaceous–Paleocene Granites from the Tengchong Block, Western Yunnan: Implications for Angle-switching of Subducting Slab显示文摘The Cenozoic geological hallmark of Western Yunnan is the characteristic voluminous Late Cretaceous-Eocene granites;however, their geological background and petrogenesis have not been well constrained and elucidated. In this study, we present new zircon U-Pb dating, along with geochemical and Sr-Nd-Hf isotopic data for granites from the Tengchong–Lianghe granitoid belt(as abbreviated to Tengliang belt) and West Yingjiang batholiths from the Tengchong block. The mineralogical and geochemical features of the Tengliang granites and the West Yingjiang batholiths are ascribed to aluminous S-type granites and weak peraluminous I-type, respectively. Zircon U-Pb analyses yielded consistent ages ranging from 67.5 Ma, 68.4 Ma and 66.2 Ma from the Tengliang granitoid belt and 50.4 Ma to 60.8 Ma for three samples from the west Yingjiang batholiths. The Tengliang granites were emplaced during the Late Cretaceous(68-66 Ma) and demonstrate negative ε_(Hf)(t) values(-24 to-4) and initial ~(87)Sr/~(86)Sr ratios of 0.7101–0.7139 and significant negative ε_(Nd)(t) values from-8.91 to-13.2, indicating a Proterozoic sedimentary source or enriched components. The hornblende-bearing I-type granites from West Yingjiang are characterized by lower initial ~(87)Sr/~(86)Sr ratios of 0.7076–0.7106, compared to Tengliang granite and negative whole-rock ε_(Nd)(t) values from-4.0 to-11.9. The early Eocene west Yingjiang gneissic granites show wide ranges of ε_(Hf)(t) values from +7.4 to-8.5 and T_(2DM) of 1.30–0.65 Ga, indicating partial melting of ancient crust with contributions of depleted mantle materials. In combination with the regional background and previous studies, we propose that such a spatio-temporal distribution of the Tengchong granitoid belt might be related to the rollback or angleswitching of the Neo-Tethyan subducting slab. This study sheds new light on the evolutionary history of the Tengchong block. | CHEN Xijie MENG Yuanku CAI Zhihui LI Huaqi LIU Xiaojia | 2022 | Acta Geologica Sinica(English Edition)2022，96，5： | 3 |
| 12 | Adakitic rocks at convergent plate boundaries:Compositions and petrogenesis显示文摘Adakitic rocks are intermediate-acid magmatic rocks characterized by enrichment in light rare-earth elements,depletion in heavy rare-earth elements,positive to negligible Eu and Sr anomalies,and high La/Yb and Sr/Y ratios.Cenozoic adakitic rocks generated by partial melting of subducted oceanic crust(slab)under eclogite-facies conditions(i.e.,the original definition of“adakite”)occur mainly in Pacific Rim volcanic arcs(intra-oceanic,continental,and continental-margin island arcs),whereas those generated by partial melting of thickened lower crust occur mainly in Tethyan Tibetan collisional orogens.In volcanic arcs,adakitic melts derived from the melting of subducted oceanic crust metasomatize the mantle wedge to form a unique rock suite comprising adakite-adakite-type high-Mg andesite-Piip-type high-Mg andesite-Nb-rich basalt-boninite.This suite differs from the basalt-andesite-dacite-rhyolite suite formed from mantle wedge metasomatized by fluids derived from subducted oceanic crust.Previously published data indicate that partial melting of mafic rocks can generate adakitic magmas under pressure,temperature,and hydrous conditions of 1.2-3.0 GPa,800-1000℃,and 1.5-6.0 wt.%H_(2)O,respectively,leaving residual minerals of garnet and rutile with little or no plagioclase.Cenozoic Au and Cu deposits occur proximally to adakitic rocks,with host rocks of some deposits actually being adakitic rocks.Adakitic rocks thus have important implications for both deep-Earth dynamics and Cu-Au mineralization/exploration.Although studies of Cenozoic adakitic rocks have made many important advances,there remain weaknesses in some important areas such as their tectonic settings,petrogenesis,magma sources,melt-mantle interactions of pre-Cenozoic adakitic rocks,and their relationship with the onset of plate tectonics and crustal growth.Future research directions are likely to involve(1)the generation of adakitic magmas by experimental simulations of partial melting of different types of rock(including intermediate-acid rocks)and magma fractional crystallization at different temperatures and pressures,(2)the relationship between magma reservoir evolution and the formation of adakitic rocks,(3)the tectonic setting and petrogenesis of pre-Cenozoic adakitic rocks and related geodynamic processes,(4)interactions between slab melts and the mantle wedge,(5)the formation of Archean adakitic tonalite-trondhjemite-granodiorite and its link to the onset of plate tectonics and crustal growth,and(6)the relationship between the formation of adakitic rocks and metal mineralization in different tectonic settings. | Qiang Wang Lulu Hao Xiuzheng Zhang Jinsheng Zhou Jun Wang Qiwei Li Lin Ma Long Zhang Yue Qi Gongjian Tang Wei Dan Jingjing Fan | 2020 | Science China Earth Sciences2020，63，12： | 3 |
| 13 | Geochronology and Geochemistry of the Early Permian A-Type Granite in the Hongol Area, Central Inner Mongolia:Petrogenesis and Tectonic Implications显示文摘We performed geochronological and geochemical analyses of the A-type granite in the Hongol area, central Inner Mongolia, to determine its age, petrogenesis and tectonic setting, which are significant for clarifying the Late Paleozoic tectonic evolution of the Xing'an Mongolian Orogenic Belt(XMOB). The rock type of the A-type granite in the Hongol area is alkali-feldspar granite, and it constitutes a western part of the Baiyinwula-Dongujimqin A-type granite belt. Zircon U-Pb geochronology yields ^(206)Pb/^(238)U ages ranging from 293 to 286 Ma for the alkali-feldspar granite, indicating this granitic pluton formed in the Early Permian. The alkali-feldspar granite is high in silica(SiO_2=75.13 wt%-80.17 wt%), aluminum(Al_2 O_3=10.59 wt%-13.17 wt%) and alkali(Na_2 O+K_2 O=7.33 wt%-9.11 wt%), and low in MgO(0.08 wt%-0.39 wt%) and CaO(0.19 wt%-0.70 wt%). It is obviously enriched in LILEs such as Rb, Th and K,depleted in HFSEs such as Nb, Ti, La and Ce, with pronounced negative anomalies of Nb, Ti, P, Eu, Sr and Ba. Its Sr-Nd-Pb isotopic compositions show positive ε_(Nd)(t)(+0.72-+3.08), low T_(DM2)(805-997 Ma),and high radioactive Pb with(^(206)Pb/^(204)Pb)_i of 18.710-19.304,(^(207)Pb/^(204)Pb)_i of 15.557-15.604 and(^(208)Pb/^(204)Pb)_i of 37.887-38.330. Petrological characteristics and geochemical data suggest that the alkalifeldspar granite in the Hongol area belongs to aluminous A-type granite. This A-type granite formed in a post-collisional extensional setting and was generated by the partial melting of felsic rocks in the middlelower crust resulting from post-collisional slab breakoff. It is suggested that the Paleo-Asian Ocean was closed before the Permian in central Inner Mongolia. | ZHANG Xiangxin GAO Yongfeng LEI Shihe | 2018 | Acta Geologica Sinica(English Edition)2018，92，3： | 3 |
| 14 | Petrogenesis of Early Carboniferous Ultramafic-Mafic Volcanic Rocks in the Southern Changning-Menglian Belt,Southeastern Tibetan Plateau:Implications for the Evolution of the Paleo-Tethyan Ocean显示文摘The Changning-Menglian Belt represents the main Paleo-Tethyan Suture in the southeastern Tibetan Plateau,which divides Gondwana-and Eurasia-derived continental fragments from each other.The belt contains ultramafic-mafic volcanic rocks that provide evidence of the tectonic processes which operated during the evolution of the Paleo-Tethyan Ocean.New geochemical data for Early Carboniferous volcanics in the southern Changning-Menglian Belt show that wehrlites have cumulate and poikilitic textures,and contain low-Fo(84.2-87.2)olivine,clinopyroxene with low Mg#values(79.4-85.6),and spinel with high Cr#values(67.8-72.4).Estimated equilibrium temperatures obtained using olivine-spinel Fe-Mg exchange geothermometry range from 978℃ to 1373℃(mean=1205℃;n=3).These observations combined with a lack of reaction or melt impregnation textures indicate that these units represent magmatic cumulates rather than having formed as a result of mantle-melt reactions.Both wehrlites and basalts in the belt have subparallel rare earth element(REE)-and primitive-mantle-normalized multi-element patterns with slightly positive Nb-Ta anomalies,but negligible Eu and Zr-Hf anomalies.The volcanics have similar Sr-Nd-Pb isotopic compositions withεNd(t)values of 4.2-4.5(mean=4.3;n=3)and 4.0-4.4(mean 4.2;n=4),respectively,and also have similar immobile element ratios,such as Nb/La,Nb/U,Th/La,Zr/Nb,Th/Ta,La/Yb,Nb/Th,Nb/Y,and Zr/Y.These characteristics indicate both units have ocean island basalt(OIB)-like geochemical affinities,consistent with the fact that the clinopyroxene in the wehrlites is compositionally similar to OIB-related cumulus clinopyroxene.This suggests that both the wehrlites and basalts were derived from similar parental magmas that underwent generally closed-system magmatic differentiation dominated by fractionation of the olivine and clinopyroxene.This parental magma was likely generated in an oceanic seamount setting from an OIB-type mantle source(i.e.,asthenospheric mantle)containing garnet-spinel lherzolite material.Combing this new data with that from oceanic seamount volcano-sedimentary suites derived from previous research enables the identification of a mature late Paleozoic ocean basin between the passive northeastern Gondwanan margin and the northward-migrating microcontinent of Lanping-Simao. | XIE Zhipeng WU Xuelu WANG Tengfei XUE Chuandong YANG Tiannan WANG Wei SUI Binxi XIN Di | 2022 | Acta Geologica Sinica(English Edition)2022，96，3： | 2 |
| 15 | Carboniferous Highly Fractionated I-type Granites from the Kalamaili Fault Zone, Eastern Xinjiang, NW China: Petrogenesis and Tectonic Implications显示文摘Carboniferous magmatism is one of the most important tectonothermal events in the Central Asian Orogenic Belt(CAOB). However, the final closure time of the Kalamaili Ocean between East Junggar and Harlik Mountain is still debated. Early Carboniferous(332 Ma) and late Carboniferous(307-298 Ma) granitic magmatism from Kalamaili fault zone have been recognized by LA-ICP-MS zircon U-Pb dating. They are both metaluminous highly fractionated I-type and belong to the high-K calc-alkaline. The granitoids for early Carboniferous have zircon εHf(t) values of-5.1 to +8.5 with Hf model ages(TDM2) of 1.78-0.83 Ga, suggesting a mixed magma source of juvenile material with old continental crust. Furthermore, those for late Carboniferous have much younger heterogeneous zircon εHf(t) values(+5.1 to +13.6) with Hf model ages(TDM2=1.03-0.45 Ga) that are also indicative of juvenile components with a small involvement of old continental crust. Based on whole-rock geochemical and zircon isotopic features, these high-K granitoids were derived from melting of heterogeneous crustal sources or through mixing of old continental crust with juvenile components and minor AFC(assimilation and fractional crystallization). The juvenile components probably originated from underplated basaltic magmas in response to asthenospheric upwelling. These Carboniferous highly fractionated granites in the Kalamaili fault zone were probably emplaced in a post-collisional extensional setting and suggested vertical continental crustal growth in the southern CAOB, which is the same or like most granitoids in CAOB. This study provides new evidence for determining the post-accretionary evolution of the southern CAOB. In combination with data from other granitoids in these two terranes, the Early Carboniferous Heiguniangshan pluton represents the initial record of post-collisional environment, suggesting that the final collision between the East Junggar and Harlik Mountain might have occurred before 332 Ma. | SONG Peng WANG Tao TONG Ying ZHANG Jianjun HUANG He ZHANG Lei QIN Qie SHEN Huan | 2019 | Acta Geologica Sinica(English Edition)2019，93，5： | 2 |
| 16 | Geochronology and Petrogenesis of Mafic-Intermediate Intrusions on the Northern Margin of the Central Tianshan(NW China): Implications for Tectonic Evolution显示文摘Late Paleozoic mafic-intermediate intrusions are widespread in the central Tianshan belt, but their tectonic settings remain controversial. Petrogenesis of these intrusions can provide insights into the tectonic evolution of the belt and its adjacent areas. This study presents new whole-rock geochemical and zircon U-Pb geochronology and Hf isotopic data for the Yaxi diorite and Qianzishan gabbro on the northern margin of the central Tianshan(NW China). Zircon U-Pb dating yielded the magma crystallization ages of 313±4 and 295±4 Ma for the Yaxi diorite and Qianzishan gabbro, respectively. They have lower Mg# values, Ni and Cr contents than typical mantle-derived primary melt, with negative correlations between MgO, TFeO and SiO2 contents, indicating clinopyroxene and olivine fractionation during magma evolution. They are characterized by enrichment of large ion lithophile elements(e.g., Rb, Ba and Sr) and depletion of high field strength elements(e.g., Nb, Ta and Ti) with high Ba/Th and Rb/Y, suggesting that their mantle sources had been metasomatized by slab-derived fluids. In addition, the Qianzishan gabbro has high Al2 O3 contents(19.54 wt.%–20.88 wt.%) and positive Eu anomalies(Eu/Eu*=1.09–1.42), which can be attributed to accumulation of plagioclase. Geochemical and zircon Hf isotopic compositions reveal that both the Yaxi diorite and Qianzishan gabbro were derived from depleted lithospheric mantle in the spinel stability field with insignificant crustal contamination. In association with previous investigations, we suggest that the Yaxi and Qianzishan intrusions were emplaced in a subduction-related environment, which means that the subduction of the Junggar Ocean lasted at least to the earliest Permian. | Hongming Cai He Yang Xiangkuan Gong | 2019 | Journal of Earth Science2019，30，2： | 2 |
| 17 | Tectonic Implications and Petrogenesis of the Various Types of Magmatic Rocks from the Zedang Area in Southern Tibet显示文摘In this study,we report systematically field observations,geochronology,whole-rock geochemistry and Sr-Nd-Hf isotopic dataset on the various types of magmatic rocks collected from the Zedang area.Chemically,the diabase and gabbro have a low-K calc-alkaline affinity,whereas the basalt and plagiogranite have medium to high-K calc-alkaline characteristics.In addition,the basalts are highly enriched in light rare earth elements(LREE)and large ion lithophile elements(LILE),but strongly depleted in high strength field elements(HFSE),indicating that their magma source probably was derived from a subduction-or arc-related setting.In contrast,both the gabbro and diabase mainly demonstrate an N-MORB-like affinity consistent with normal mid-oceanic ridge basalt(N-MORB)origin.The zircon U-Pb dating results suggest that the basalts were crystallized earlier at ca.158–161 Ma(Oxfordian stage),but the gabbro was crystallized at ca.131 Ma(Hauterivian stage of Early Cretaceous).The zircon U-Pb dating results correspond with the field observations that the veins of gabbro intruded basalt.Furthermore,the plagiogranite has a weighted mean age of ca.160 Ma(MSWD=2.1)consistent with the basalt within the uncertainty.The basalt and the plagiogranite have significantly positiveεHf(t)values(+5.8 to+15.6 and+8.6 to+16.1,respectively),suggesting that they were originated from partial melting of a depleted source.However,basalt and plagiogranite are characterized by the wide variations ofεHf(t)values indicating minor amounts of exotic crustal material input during the later magma evolution.Additionally,the basalt shows duplex geochemical features of island-arc and mid-oceanic ridge basalt,corresponding to the supra-subduction zone-(SSZ)type affinity.To sum up,two distinct magmatic events identified in this study probably suggest an intra-oceanic arc system existing in the Zedang area during the Late Jurassic,but the intra-oceanic arc subduction extinguished in the Early Cretaceous as suggested by the N-MORB-like gabbro and diabase.Integrated with regional background and different rock types,as well as geochemical features,we conclude that intra-oceanic arc subduction setting developed during the Late Jurassic in the Zedang area,southern Tibet. | Yuanku Mengc Fahui Xiong Jingsui Yang Zhao Liu Kieran AIles Paul TRobinson Xiangzhen Xu | 2019 | Journal of Earth Science2019，30，6： | 2 |
| 18 | Geochemistry and Petrogenesis of the ca. 2.5Ga High-K Granitoids in the Southern North China Craton显示文摘Archean high-K granitoids, generally formed after tonalite-trondhjemite-granodiorite (TTGs), are important for understanding crustal reworking of ancient cratons. The Linshan Archean high-K granitoids from the southern Trans-North China Orogen (TNCO) provide a window into the conti-nental crustal evolution of the North China Craton (NCC). They mainly consist of monzogranite and granodiorite which were formed during 2 542-2 503 Ma. The high-K granitoids have high SiO2 (65.86wt.%-78.08wt.%), K2O (3.29 wt.%-7.62wt.%) and low P2O5 (0.01 wt.%-0.27wt.%). They display right inclined REE patterns with negative Eu anomalies (Eu/Eu*=0.20-0.81).Their spider diagram is characterized by enrichment of Rb, K, Th, U and depletion of Nb, Ta, Zr, Ti. The rocks have positive and variable zircon εHf(t)(+2.5 to +6.6) and whole-rock εHf(t)(+0.7 to +4.5) with two-stage model ages (TDM2^Hf=2.87-2.64 Ga;TDM2^Nd=2.77-2.50 Ga) similar to those of the Archean TTG-ty pe rocks, amphibolites and diorites in the area. These evidences suggest that the high-K granitoids were produced by partial melting of juvenile crustal rocks. The Linshan high-K granitoids show relatively high whole-rock zircon saturation tempera-tures (694-889℃) and low Sr/Y ratios (0.27-21.1), indicating low pressure partial melting. Combined with other geological evidences, the Linshan high-K granitoids are suggested to have been produced by partial melting of the continental crust in a post-collision extensional environment after an arc-continent collision. Thus, the NCC did not amalgamate together until ca. 2.5 Ga. Compiled zircon U-Pb ages and Hf isotopes reveal that the ca. 2.5 Ga magmatism represents reworking of the continental crust. | Lei Li Wenjian Zhai | 2019 | Journal of Earth Science2019，30，3： | 2 |
| 19 | Baossi–Warack monogenetic volcanoes, Adamawa Plateau,Cameroon: petrography, mineralogy and geochemistry显示文摘Three monogenetic cones in the Baossi–Warack area, Ngaoundéré, Adamawa Plateau forming part of the Cameroon Volcanic Line(CVL) are documented in this study. Basaltic lavas(<1 km^3) scattered around these vents and restricted volcaniclastic deposits were emplaced by Hawaiian and mild strombolian style eruptions. The lavas are porphyritic, mainly composed of olivine(chrysolite) and clinopyroxene(diopside and augite) phenocrysts and plagioclase(andesine) microphenocrysts. Accessory minerals include titano-magnetite and titano-hematite, nepheline,apatite and amphibole xenocrysts. Sanidine occurs in some samples and sodi-potassic albite in others. Some olivines and clinopyroxenes exhibit resorbed margins and thin reaction rims while plagioclase displays oscillatory zoning, and sieved textures as a result of magma mixing. Whole-rock geochemistry data indicates that the lavas are silica-undersaturated, composed of basanites and basalts, showing little compositional variations(SiO_2: 39.20 wt.%–48.01 wt.%,MgO: 5.29 wt.%–9.70 wt.%). Trace elements patterns of these lavas suggest they are enriched in LILE including Pb,probably due to crustal contamination. REE patterns suggest cogenetic magmas below Baossi 1 and Baossi 2 volcanoes,and distinct sources below Warack volcano and nearby lavas.The lavas studied show affinity to high-μ(HIMU), enriched type Ⅰ(EM1) and Oceanic Island Basalt(OIB)-like mantle signatures and thus indicate a heterogeneous mantle source underneath the vents as noted at other monogenetic and polygenetic volcanoes along the CVL. Primary melts derived from low degrees of partial melting(0.5%–2%) and encountered low rates of fractionation, and crustal contamination coupled with magma mixing. These melts evolved independently through structural weaknesses in the basement. | Anicet Feudjio Tiabou Robert Temdjim Pierre Wandji Jacques-Marie Bardintzeff Vivian Bih Che Edith Ekatah Bate Tibang Caroline Neh Ngwa Fran?ois Xavier Onana Mebara | 2019 | Acta Geochimica2019，38，1： | 2 |
| 20 | Zircon U-Pb geochronology,geochemistry and geological significance of Xiarihamu granodiorite in Eastern Kunlun orogenic belt,Qinghai显示文摘Zircon U-Pb geochronology and geochemistry of the granodiorites in Xiarihamu Cu-Ni mining area are studied to determine the formation age,genesis and tectonic setting. The results show that the granodiorites formed in the Middle Triassic with weighted average age of 242 ± 1 Ma. The granodiorites comprise of SiO_2 of 61. 34%--62. 54%,Al_2 O_3 of 16. 46%--16. 87%,MgO of 2. 37%--2. 66%,( Na_2 O + K_2 O) of 5. 39%--5. 74%with the Na2 O/K_2 O of 1. 46--1. 88,Mg~# of 47. 03--48. 04,and show metaluminous characteristics with A/CNK of 0. 94--0. 96,belonging to calc-alkaline I-type granites geochemically. The light and heavy rare earth elements in the rocks are distinctly fractionated and have ' right-inclined' distribution patterns with weak negative Eu anomalies( δEu = 0. 84--0. 91). Moreover,these samples show enrichments in LILEs( e. g.,Rb,Ba,K and Sr),especially in Sr [( 343--452) × 10^(-6)],and obvious depletions in HFSEs( e. g.,Nb,Ta,Ti and P),indicating geochemical characteristics similar to subduction-related magmatic rocks. According to the regional tectonic evolution,the Xiarihamu granodiorites were emplaced under an Andean-type active continental margin environment in the early Indosinian,possessing a crust-mantle mixing origin. | YANG Baorong MA Zhongxian ZHANG Libin WANG Xiaoyun YAN Zhengping | 2018 | Global Geology2018，21，4： | 1 |
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