Geodynamic mechanism responsible for the generation of Silurian granitoids and the tectonic evolution of the Qilian orogenic belt remains controversial. In this study, we report the results of zircon U–Pb age, and sy...Geodynamic mechanism responsible for the generation of Silurian granitoids and the tectonic evolution of the Qilian orogenic belt remains controversial. In this study, we report the results of zircon U–Pb age, and systematic whole-rock geochemical data for the Haoquangou and Liujiaxia granitoids within the North Qilian orogenic belt and the Qilian Block, respectively, to constrain their petrogenesis, and the Silurian tectonic evolution of the Qilian orogenic belt. Zircon U–Pb ages indicate that the Haoquangou and Liujiaxia intrusions were emplaced at423 ± 3 Ma and 432 ± 4 Ma, respectively. The Haoquangou granodiorites are calc-alkaline, while the Liujiaxia granites belong to the high-K calc-alkaline series.Both are peraluminous in composition and have relatively depleted Nd isotopic [ε_(Nd)(t) =(-3.9 – + 0.6)] characteristics compared with regional basement rocks, implying their derivation from a juvenile lower crust. They show adakitic geochemical characteristics and were generated by partial melting of thickened lower continental crust. Postcollisional extensional regime related to lithospheric delamination was the most likely geodynamic mechanism for the generation of the Haoquangou granodiorite, while the Liujiaxia granites were generated in a compressive setting during continental collision between the Qaidam and Qilian blocks.展开更多
There are a large number of Mesozoic intrusive and volcanic rocks in western Liaoning of China,which is an ideal place to study the Mesozoic Paleo-Pacific subduction processes,and lithospheric destruc-tion of North Ch...There are a large number of Mesozoic intrusive and volcanic rocks in western Liaoning of China,which is an ideal place to study the Mesozoic Paleo-Pacific subduction processes,and lithospheric destruc-tion of North China Craton.Detailed petrographic,zircon U-Pb dating and geochemical studies of the Early Jurassic granites in Huashan pluton,Xingcheng,western Liaoning,indicate that the Early Jurassic granites were formed at 184-174 Ma,mainly composed of syenite and monzogranite.The geochemical characteristics show high contents of SiO_(2),Al_(2)O_(3)and Na_(2)O+K_(2)O,low contents of Fe_(2)O_(3)and MgO,enrichment in LREEs and LILEs,and depletion in HREEs and HFSEs,and have a high content of Sr and low contents of Y and Yb,with weak negative Eu anomalies and slightly negative anomalies of Ce,indicating that they are a set of intermediate-acidic adakitic granites in high-K calc-alkaline series.All the facts significantly suggest that the Early Jurassic adakitic granites were formed at the active continental margin in the context of Paleo-Pacific plate subduction.展开更多
Volcanic rocks with adakitic compositional signature have been recognized in the northern margin of ancient Junggar island arc for the Late Paleozoic. These adakites for the early Devonian from the Tuoranggekudouke Gr...Volcanic rocks with adakitic compositional signature have been recognized in the northern margin of ancient Junggar island arc for the Late Paleozoic. These adakites for the early Devonian from the Tuoranggekudouke Group (D1t) are characteristic of high Sr, Sr/Y and (La/Yb)N but low Y, Yb and HREE. Their compositional characteristics are much similar to those of the typical adakites in the world but distinct from those of the normal arc volcanic rocks from the same Group. We conclude that these adakitic volcanic rocks were produced by slab melting during the early period of Paleoasia-ocean lithosphere subduction. This infers that the Paleoasia Ocean in the north Junggar area began a new subduction process in the early Devonian.展开更多
Eocene intermediate to felsic subvolcanic rocks of the Torud-Ahmad Abad magmatic belt(TAMB),in the northern part of the Central Iran zone,are exposed between the Torud and Ahmad Abad regions in South-Southeast Shahroo...Eocene intermediate to felsic subvolcanic rocks of the Torud-Ahmad Abad magmatic belt(TAMB),in the northern part of the Central Iran zone,are exposed between the Torud and Ahmad Abad regions in South-Southeast Shahrood.These igneous rocks include hypabyssal dacite,trachyte,andesite,trachy-andesite,and basaltic andesite;they are mainly composed of phenocrysts and microcrystalline groundmass of pyroxene,amphibole,and plagioclase,with minor biotite and titanomagnetite;they form domal structures(plugs and stocks),dikes,and sills that intruded into Neoproterozoic to cogenetic Eocene volcano-sedimentary sequences.Based on isotopic analysis of these intermediate to acidic rocks,initial ratios of^(143)Nd/^(144)Nd range from 0.512775 to 0.512893 and initial ratios of^(87)Sr/^(86)Sr range from 0.703746 to 0.705314,with quite positiveε_(Nd(i))values of+3.69 to+6.00.They are enriched in light rare earth elements and large ion lithophile elements and depleted in heavy rare earth elements and high-field strength elements,the SiO_(2) content is(52-62)wt.%,and Na_(2)O content>3 wt.%,Al_(2)O_(3) content>16 wt.%,Yb<1.8 ppm,and Y<18 ppm.These geological,geochemical,and Sr and Nd isotopic data are consistent with adakitic signatures originating by partial melting of the subducted Neo-Tethys oceanic slab(Sabzevar branch)and lithospheric suprasubduction zone mantle.The mantle signatures typifying the rapidly emplaced adakitic rocks(slab(high-silica adakite)and suprasubduction zone(low-silica adakite)melts)together with their locally voluminous extent are evidences that support a locally extensional geodynamic setting;and the evidence is consistent with an evolution to local transpression in the Late Eocene in this convergent margin are environment to rifting(basalts to adakites)towards submarine conditions in the Neogene.展开更多
The Geza arc is an important part of the Sanjiang tectono-magmatic belt and is a newly discovered copper polymetallic ore concentration area in northwest Yunnan province,Southwest China.The area comprises numerous met...The Geza arc is an important part of the Sanjiang tectono-magmatic belt and is a newly discovered copper polymetallic ore concentration area in northwest Yunnan province,Southwest China.The area comprises numerous metal ore deposits,including one super-largedeposit,three large deposits,etc.The formation of these deposits was closely related to intermediate–acidic magmatic intrusions.Based on previous studies,the“big data”analysis technique was used for a comparative study of large geochemical datasets of granite related to ore-formation in the Geza porphyry copper deposit and global adakites.As a result,1313 element combinations and 127,765 overlap ratios were obtained.The results show that the Geza porphyry has similar geochemical characteristics to global adakites(the ratios of REE and Ga to major elements are in the range of global adakites).However,theCu,Mo,and Zn contents of the porphyry are significantly higher than those of global adakites,and the porphyry may,therefore,represent an end-member of the global range of adakite composition.In addition,the geochemistry of adakites associated with the porphyry copper deposits overlaps in part with that of global adakites,although most of the data lie outside of the range of global adakites(i.e.lowMn/Cu,Sr/Cu,Na/Cu,and Zr/Cu values,and high Th/Cu,Ba/Cu,Na/Mo,Rb/Mo,Th/Mo,Ta/Mo,Ba/Mo,Mn/Zn,and Ba/Znvalues).The samples with characteristics that deviate significantly from the geochemistry of global adakites show more advanced mineralization and alteration,and a stronger relationship with Cu and Momineralization.The results of geochemical data mining can be used as a prospecting indicator,and provide a new scientific basis for geological prospecting of the deep levels and per-iphery of the Geza Cu polymetallic ore belt.展开更多
Late Neoproterozoic adakitic magmatism within the Eastern Arabian Nubian Shield has been dated at633.2±9.0 Ma(2σ).These magnas intrude the forearc Ad Dawadimi Basin,which is composed of metapelitic schists and g...Late Neoproterozoic adakitic magmatism within the Eastern Arabian Nubian Shield has been dated at633.2±9.0 Ma(2σ).These magnas intrude the forearc Ad Dawadimi Basin,which is composed of metapelitic schists and greywacke along with ophiolitic melanges of boninitic affinity which underwent inversion and deformation by^620 Ma.This adakitic magmatism,while intruding parts of the Ad Dawadimi Basin,predates this deformation,but is possibly coincident with basin closure.As adakitic magmatism requires melting of an amphibolite or eclogitic source,empirical and experimental constraints require anomalously hot supra-subduction zone mantle.Considering that this magmatism immediately predates basin inversion,these magmas possibly pinpoint the timing of the slab breaking,marking the terminal stages of arc magmatism,terrane accretion and the influx of hot oceanic asthenospheric mantle.This influx of hot asthenospheric mantle may also be responsible for postcolltsional A-type magmatism.展开更多
Changes in oceanic O-Sr-C isotopic compositions, global cooling and Asian continental aridification beginning in the Middle-Late Eocene(47-34 Ma) are considered to have been caused by the uplift of the Tibetan plateau...Changes in oceanic O-Sr-C isotopic compositions, global cooling and Asian continental aridification beginning in the Middle-Late Eocene(47-34 Ma) are considered to have been caused by the uplift of the Tibetan plateau.The specific timing and uplift mechanism,however,have long been subjects of debate.We investigated the Duogecuoren lavas of the central-western Qiangtang block,which form the largest outcrops among Cenozoic lavas in north-展开更多
In this paper, we report new whole-rock geochemical and zircon U–Pb data for monzogranites in the NE Xing'an block. These data constrained the petrogenesis of C type(high Sr/Y) adakitic rocks and showed the spati...In this paper, we report new whole-rock geochemical and zircon U–Pb data for monzogranites in the NE Xing'an block. These data constrained the petrogenesis of C type(high Sr/Y) adakitic rocks and showed the spatial extent of the influence of the Mongol-Okhostsk ocean tectonic regime and the collision between the Jiamusi Massif and Songliao Terrane. New zircon laser-ablation inductivity coupled plasma mass spectrometry(LA-ICP-MS) U–Pb data indicated that the monzogranites in the studied area were emplaced in the Early Jurassic(~180 Ma). These rocks were characterized by unusally high SiO_2(C67.49), and Sr(461–759 ppm), but strikingly low Y(4.63–8.06 ppm) and HREE(P HREE = 3.83–6.49 ppm, Yb = 0.5–0.77 ppm)contents, with therefore high Sr/Y(67.2–119) and(La/Yb)N(29.7–41.5) ratios, showing the geochemical characteristics of C type adakitic granite. The data displayed negligible Eu anomalies(Eu/Eu~ = 0.77–1.08), LREE-enriched and pronounced negative Nb and Ta anomalies. The C-typeadakites in the studied area were most likely derived from the partial melting of a thickened lower continental curst. The magma source is most likely dominated by amphibolites and garnet amphibolites. In combination with previously-reported data from igneous rocks from the Mesozoic in NE China, we conclude that the Xing'an block was influenced by the Mongol-Okhotsk subduction tectonic system, and experiences compressive settings from the amalgamation of the Jiamusi block in the east of the CAOB.展开更多
基金funded by Gansu Provincial Natural Science Foundation (Grant Numbers 21JR7RA503 and22JR5RA819)the Fundamental Research Funds for the Central Universities (Grant lzujbky-2021-ct07)+1 种基金the Key Talent Project of Gansu Province (2022-Yangzhenxi)the National Second Expedition to the Tibetan Plateau (2019QZKK0704)。
文摘Geodynamic mechanism responsible for the generation of Silurian granitoids and the tectonic evolution of the Qilian orogenic belt remains controversial. In this study, we report the results of zircon U–Pb age, and systematic whole-rock geochemical data for the Haoquangou and Liujiaxia granitoids within the North Qilian orogenic belt and the Qilian Block, respectively, to constrain their petrogenesis, and the Silurian tectonic evolution of the Qilian orogenic belt. Zircon U–Pb ages indicate that the Haoquangou and Liujiaxia intrusions were emplaced at423 ± 3 Ma and 432 ± 4 Ma, respectively. The Haoquangou granodiorites are calc-alkaline, while the Liujiaxia granites belong to the high-K calc-alkaline series.Both are peraluminous in composition and have relatively depleted Nd isotopic [ε_(Nd)(t) =(-3.9 – + 0.6)] characteristics compared with regional basement rocks, implying their derivation from a juvenile lower crust. They show adakitic geochemical characteristics and were generated by partial melting of thickened lower continental crust. Postcollisional extensional regime related to lithospheric delamination was the most likely geodynamic mechanism for the generation of the Haoquangou granodiorite, while the Liujiaxia granites were generated in a compressive setting during continental collision between the Qaidam and Qilian blocks.
基金Supported by the National Key R&D Program of China(No.2016YFC0666108-02).
文摘There are a large number of Mesozoic intrusive and volcanic rocks in western Liaoning of China,which is an ideal place to study the Mesozoic Paleo-Pacific subduction processes,and lithospheric destruc-tion of North China Craton.Detailed petrographic,zircon U-Pb dating and geochemical studies of the Early Jurassic granites in Huashan pluton,Xingcheng,western Liaoning,indicate that the Early Jurassic granites were formed at 184-174 Ma,mainly composed of syenite and monzogranite.The geochemical characteristics show high contents of SiO_(2),Al_(2)O_(3)and Na_(2)O+K_(2)O,low contents of Fe_(2)O_(3)and MgO,enrichment in LREEs and LILEs,and depletion in HREEs and HFSEs,and have a high content of Sr and low contents of Y and Yb,with weak negative Eu anomalies and slightly negative anomalies of Ce,indicating that they are a set of intermediate-acidic adakitic granites in high-K calc-alkaline series.All the facts significantly suggest that the Early Jurassic adakitic granites were formed at the active continental margin in the context of Paleo-Pacific plate subduction.
基金This work was supported by the National "305" Program (Grant No. 96-915-01-01).
文摘Volcanic rocks with adakitic compositional signature have been recognized in the northern margin of ancient Junggar island arc for the Late Paleozoic. These adakites for the early Devonian from the Tuoranggekudouke Group (D1t) are characteristic of high Sr, Sr/Y and (La/Yb)N but low Y, Yb and HREE. Their compositional characteristics are much similar to those of the typical adakites in the world but distinct from those of the normal arc volcanic rocks from the same Group. We conclude that these adakitic volcanic rocks were produced by slab melting during the early period of Paleoasia-ocean lithosphere subduction. This infers that the Paleoasia Ocean in the north Junggar area began a new subduction process in the early Devonian.
基金supported by the NSERC Discovery to David R.Lentz。
文摘Eocene intermediate to felsic subvolcanic rocks of the Torud-Ahmad Abad magmatic belt(TAMB),in the northern part of the Central Iran zone,are exposed between the Torud and Ahmad Abad regions in South-Southeast Shahrood.These igneous rocks include hypabyssal dacite,trachyte,andesite,trachy-andesite,and basaltic andesite;they are mainly composed of phenocrysts and microcrystalline groundmass of pyroxene,amphibole,and plagioclase,with minor biotite and titanomagnetite;they form domal structures(plugs and stocks),dikes,and sills that intruded into Neoproterozoic to cogenetic Eocene volcano-sedimentary sequences.Based on isotopic analysis of these intermediate to acidic rocks,initial ratios of^(143)Nd/^(144)Nd range from 0.512775 to 0.512893 and initial ratios of^(87)Sr/^(86)Sr range from 0.703746 to 0.705314,with quite positiveε_(Nd(i))values of+3.69 to+6.00.They are enriched in light rare earth elements and large ion lithophile elements and depleted in heavy rare earth elements and high-field strength elements,the SiO_(2) content is(52-62)wt.%,and Na_(2)O content>3 wt.%,Al_(2)O_(3) content>16 wt.%,Yb<1.8 ppm,and Y<18 ppm.These geological,geochemical,and Sr and Nd isotopic data are consistent with adakitic signatures originating by partial melting of the subducted Neo-Tethys oceanic slab(Sabzevar branch)and lithospheric suprasubduction zone mantle.The mantle signatures typifying the rapidly emplaced adakitic rocks(slab(high-silica adakite)and suprasubduction zone(low-silica adakite)melts)together with their locally voluminous extent are evidences that support a locally extensional geodynamic setting;and the evidence is consistent with an evolution to local transpression in the Late Eocene in this convergent margin are environment to rifting(basalts to adakites)towards submarine conditions in the Neogene.
基金This paper is supported by the Key Laboratory of Geological Information Technology,Ministry of Natural Resources of the People’s Repbulic of China[Grant No:KKF0201821043]Natural Science Foundation of China[Grant No.41862009]+1 种基金Science and Technology Award of Yunnan Province-Outstanding Contribution award Project[Grant No.2007001]Key disciplines construction funding project of Kunming University of Science and Technology[1407839305].
文摘The Geza arc is an important part of the Sanjiang tectono-magmatic belt and is a newly discovered copper polymetallic ore concentration area in northwest Yunnan province,Southwest China.The area comprises numerous metal ore deposits,including one super-largedeposit,three large deposits,etc.The formation of these deposits was closely related to intermediate–acidic magmatic intrusions.Based on previous studies,the“big data”analysis technique was used for a comparative study of large geochemical datasets of granite related to ore-formation in the Geza porphyry copper deposit and global adakites.As a result,1313 element combinations and 127,765 overlap ratios were obtained.The results show that the Geza porphyry has similar geochemical characteristics to global adakites(the ratios of REE and Ga to major elements are in the range of global adakites).However,theCu,Mo,and Zn contents of the porphyry are significantly higher than those of global adakites,and the porphyry may,therefore,represent an end-member of the global range of adakite composition.In addition,the geochemistry of adakites associated with the porphyry copper deposits overlaps in part with that of global adakites,although most of the data lie outside of the range of global adakites(i.e.lowMn/Cu,Sr/Cu,Na/Cu,and Zr/Cu values,and high Th/Cu,Ba/Cu,Na/Mo,Rb/Mo,Th/Mo,Ta/Mo,Ba/Mo,Mn/Zn,and Ba/Znvalues).The samples with characteristics that deviate significantly from the geochemistry of global adakites show more advanced mineralization and alteration,and a stronger relationship with Cu and Momineralization.The results of geochemical data mining can be used as a prospecting indicator,and provide a new scientific basis for geological prospecting of the deep levels and per-iphery of the Geza Cu polymetallic ore belt.
文摘Late Neoproterozoic adakitic magmatism within the Eastern Arabian Nubian Shield has been dated at633.2±9.0 Ma(2σ).These magnas intrude the forearc Ad Dawadimi Basin,which is composed of metapelitic schists and greywacke along with ophiolitic melanges of boninitic affinity which underwent inversion and deformation by^620 Ma.This adakitic magmatism,while intruding parts of the Ad Dawadimi Basin,predates this deformation,but is possibly coincident with basin closure.As adakitic magmatism requires melting of an amphibolite or eclogitic source,empirical and experimental constraints require anomalously hot supra-subduction zone mantle.Considering that this magmatism immediately predates basin inversion,these magmas possibly pinpoint the timing of the slab breaking,marking the terminal stages of arc magmatism,terrane accretion and the influx of hot oceanic asthenospheric mantle.This influx of hot asthenospheric mantle may also be responsible for postcolltsional A-type magmatism.
文摘Changes in oceanic O-Sr-C isotopic compositions, global cooling and Asian continental aridification beginning in the Middle-Late Eocene(47-34 Ma) are considered to have been caused by the uplift of the Tibetan plateau.The specific timing and uplift mechanism,however,have long been subjects of debate.We investigated the Duogecuoren lavas of the central-western Qiangtang block,which form the largest outcrops among Cenozoic lavas in north-
基金supported by the regional geology and mineralization research program of Heilongjiang province (HLJKD201417)
文摘In this paper, we report new whole-rock geochemical and zircon U–Pb data for monzogranites in the NE Xing'an block. These data constrained the petrogenesis of C type(high Sr/Y) adakitic rocks and showed the spatial extent of the influence of the Mongol-Okhostsk ocean tectonic regime and the collision between the Jiamusi Massif and Songliao Terrane. New zircon laser-ablation inductivity coupled plasma mass spectrometry(LA-ICP-MS) U–Pb data indicated that the monzogranites in the studied area were emplaced in the Early Jurassic(~180 Ma). These rocks were characterized by unusally high SiO_2(C67.49), and Sr(461–759 ppm), but strikingly low Y(4.63–8.06 ppm) and HREE(P HREE = 3.83–6.49 ppm, Yb = 0.5–0.77 ppm)contents, with therefore high Sr/Y(67.2–119) and(La/Yb)N(29.7–41.5) ratios, showing the geochemical characteristics of C type adakitic granite. The data displayed negligible Eu anomalies(Eu/Eu~ = 0.77–1.08), LREE-enriched and pronounced negative Nb and Ta anomalies. The C-typeadakites in the studied area were most likely derived from the partial melting of a thickened lower continental curst. The magma source is most likely dominated by amphibolites and garnet amphibolites. In combination with previously-reported data from igneous rocks from the Mesozoic in NE China, we conclude that the Xing'an block was influenced by the Mongol-Okhotsk subduction tectonic system, and experiences compressive settings from the amalgamation of the Jiamusi block in the east of the CAOB.
