Late Mesozoic volcanic-subvolcanic rocks and related iron deposits, known as porphyry iron deposits in China, are widespread in the Ningwu ore district （Cretaceous basin） of the middle-lower Yangtze River polymetall...Late Mesozoic volcanic-subvolcanic rocks and related iron deposits, known as porphyry iron deposits in China, are widespread in the Ningwu ore district （Cretaceous basin） of the middle-lower Yangtze River polymetallic ore belt, East China. Two types of Late Mesozoic magmatic rocks are exposed： one is dioritic rocks closely related to iron mineralization as the hosted rock, and the other one is granodioritic （-granitic） rocks that cut the ore bodies. To understand the age of the iron mineralization and the ore-forming event, detailed zircon U-Pb dating and Hf isotope measurement were performed on granodioritic stocks in the Washan, Gaocun-Nanshan, Dongshan and Heshangqiao iron deposits in the basin. Four emplacement and crystallization （typically for zircons） ages of granodioritic rocks were measured as 126.1±0.5 Ma, 126.8±0.5 Ma, 127.3±0.5 Ma and 126.3±0.4 Ma, respectively in these four deposits, with the LA-MC-ICP-MS zircon U-Pb method. Based on the above results combined with previous dating, it is inferred that the iron deposits in the Ningwu Cretaceous basin occurred in a very short period of 131-127 Ma. In situ zircon Hf compositions of εHf（t） of the granodiorite are mainly from -3 to -8 and their corresponding 176Hf/177Hf ratio are from 0.28245 to 0.28265, indicating similar characteristics of dioritic rocks in the basin. We infer that granodioritic rocks occurring in the Ningwu ore district have an original relationship with dioritic rocks. These new results provide significant evidence for further study of this ore district so as to understand the ore-forming event in the study area.展开更多
The Gebunongba iron polymetallic deposit is a typical skarn deposit located at the westernmost end of the discovered iron polymetallic deposits in the Gangdese metallogenic belt. Major and trace elements of the monzon...The Gebunongba iron polymetallic deposit is a typical skarn deposit located at the westernmost end of the discovered iron polymetallic deposits in the Gangdese metallogenic belt. Major and trace elements of the monzonite granite related to mineralization show that these rocks are peraluminous(ACNK=1.15–1.21) and are rich in Si(76.63 wt.%–76.93 wt.% SiO2), K(K2 O/Na2 O ratio of 1.80–2.30), LREE and LILEs(Rb, Ba, Th, U, Pb), but is depleted in high field strength elements(Nb, Ta, Ti and HREE). In addition, these rocks show obviously negative Eu anomalies(δEu=0.48–0.55). The LA-ICPMS U-Pb age of zircons in monzonite granite is 59.72±0.55 Ma(MSWD=0.79), whereas the 40 Ar/39 Ar age of muscovite in iron ores is 59.22±0.61 Ma(MSWD=16.20). This indicates that the deposit formed at the syn-collision stage of Lhasa-India terrane is later than the northward subduction of the Yajiang crust. The monzonite granite has been probably derived from the partial melting of ancient lower crustal materials, which is probably resulted from the underplating of mantle-derived magmas. It is favorable for the formation of iron polymetallic deposit. Iron polymetallic mineralization is prevalent in Gangdese metallogenic belt at syn-collision stage. Therefore, syn-collision stage is an important mineralization stage for iron polymetallic deposits. The results of this study proved that iron polymetallic mineralization still took place in the western segment of Gangdese metallogenic belt and provided basis for further prospecting the deposits of the same type.展开更多
This paper reports an integrated study of in situ U-Pb geochronology and elemental geochemistry of zircons from the Xianglushan iron-polymetallic deposit in western Guizhou Province, Southwest China. Genetic relations...This paper reports an integrated study of in situ U-Pb geochronology and elemental geochemistry of zircons from the Xianglushan iron-polymetallic deposit in western Guizhou Province, Southwest China. Genetic relationship between this new type of deposit and unroofing of the Emeishan large igneous province(ELIP) is focused. Along with the zoning pattern in spatial distribution of diverse weathering-related deposits along the southern and southeastern margins of the ELIP, it is suggested that the genesis of the iron-polymetallic deposit was specialized by factors of coastal paleogeography in hot-humid climate, where iron-enriched laterites formed, and repetitive marine transgression-regression occurred during the Late Permian.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 40930419)the National Special Research Programs for Non-Profit Trades (Sponsored by MLR, Grant Nos. 200911007 and 200811114)Open Foundation of State Key laboratory of Geological Processes and Mineral Resources, School of the Earth Sciences and Resources, China University of Geosciences, Beijing (Grant No. GPMR201029)
文摘Late Mesozoic volcanic-subvolcanic rocks and related iron deposits, known as porphyry iron deposits in China, are widespread in the Ningwu ore district （Cretaceous basin） of the middle-lower Yangtze River polymetallic ore belt, East China. Two types of Late Mesozoic magmatic rocks are exposed： one is dioritic rocks closely related to iron mineralization as the hosted rock, and the other one is granodioritic （-granitic） rocks that cut the ore bodies. To understand the age of the iron mineralization and the ore-forming event, detailed zircon U-Pb dating and Hf isotope measurement were performed on granodioritic stocks in the Washan, Gaocun-Nanshan, Dongshan and Heshangqiao iron deposits in the basin. Four emplacement and crystallization （typically for zircons） ages of granodioritic rocks were measured as 126.1±0.5 Ma, 126.8±0.5 Ma, 127.3±0.5 Ma and 126.3±0.4 Ma, respectively in these four deposits, with the LA-MC-ICP-MS zircon U-Pb method. Based on the above results combined with previous dating, it is inferred that the iron deposits in the Ningwu Cretaceous basin occurred in a very short period of 131-127 Ma. In situ zircon Hf compositions of εHf（t） of the granodiorite are mainly from -3 to -8 and their corresponding 176Hf/177Hf ratio are from 0.28245 to 0.28265, indicating similar characteristics of dioritic rocks in the basin. We infer that granodioritic rocks occurring in the Ningwu ore district have an original relationship with dioritic rocks. These new results provide significant evidence for further study of this ore district so as to understand the ore-forming event in the study area.
基金jointly funded by the National Key Research and Development Program (No. 2016YFC0600300)the Fundamental Scientific Research Fund for Central Universities+1 种基金Changjiang Scholars ProgramInnovation Team Development Plan (No. IRT1083)
文摘The Gebunongba iron polymetallic deposit is a typical skarn deposit located at the westernmost end of the discovered iron polymetallic deposits in the Gangdese metallogenic belt. Major and trace elements of the monzonite granite related to mineralization show that these rocks are peraluminous(ACNK=1.15–1.21) and are rich in Si(76.63 wt.%–76.93 wt.% SiO2), K(K2 O/Na2 O ratio of 1.80–2.30), LREE and LILEs(Rb, Ba, Th, U, Pb), but is depleted in high field strength elements(Nb, Ta, Ti and HREE). In addition, these rocks show obviously negative Eu anomalies(δEu=0.48–0.55). The LA-ICPMS U-Pb age of zircons in monzonite granite is 59.72±0.55 Ma(MSWD=0.79), whereas the 40 Ar/39 Ar age of muscovite in iron ores is 59.22±0.61 Ma(MSWD=16.20). This indicates that the deposit formed at the syn-collision stage of Lhasa-India terrane is later than the northward subduction of the Yajiang crust. The monzonite granite has been probably derived from the partial melting of ancient lower crustal materials, which is probably resulted from the underplating of mantle-derived magmas. It is favorable for the formation of iron polymetallic deposit. Iron polymetallic mineralization is prevalent in Gangdese metallogenic belt at syn-collision stage. Therefore, syn-collision stage is an important mineralization stage for iron polymetallic deposits. The results of this study proved that iron polymetallic mineralization still took place in the western segment of Gangdese metallogenic belt and provided basis for further prospecting the deposits of the same type.
基金supported by the National Natural Science Foundation of China(Grant Nos.41373037 and 41173048)Integrated Exploration Project of the Weining-Shuicheng Iron-Polymetallic Deposits,Guizhou Province
文摘This paper reports an integrated study of in situ U-Pb geochronology and elemental geochemistry of zircons from the Xianglushan iron-polymetallic deposit in western Guizhou Province, Southwest China. Genetic relationship between this new type of deposit and unroofing of the Emeishan large igneous province(ELIP) is focused. Along with the zoning pattern in spatial distribution of diverse weathering-related deposits along the southern and southeastern margins of the ELIP, it is suggested that the genesis of the iron-polymetallic deposit was specialized by factors of coastal paleogeography in hot-humid climate, where iron-enriched laterites formed, and repetitive marine transgression-regression occurred during the Late Permian.
