An isotopic study was systemically carried out on the granitic complex,diorite-porphyrite, ores and ore minerals of the 103 Ma Xiaoxinancha gold-rich copper deposit in Jilin province to determine the geodynamic model ...An isotopic study was systemically carried out on the granitic complex,diorite-porphyrite, ores and ore minerals of the 103 Ma Xiaoxinancha gold-rich copper deposit in Jilin province to determine the geodynamic model of diagenesis and metallogenesis.Results show that the initial Nd and Sr isotopic compositions of the granitic complex are in the range of 0.70425-0.70505 for（87Sr/86Sr）i, 0.51243-0.51264 for INd,and -1.31 to ＋2.64 forεNd（t）;those of the diorite-porphyrite are in the range from 0.70438-0.70448 for（87Sr/86Sr）,,0.51259-0.51261 for INd,and ＋1.56 to ＋2.09 forεNd（t）.For ores and sulfides,the（87Sr/86Sr）i,7Nd,andεNd（t） values are in the range from 0.70440-0.70805,0.51259- 0.51279 and ＋1.72 to ＋5.56,respectively.The Pb isotopic ratios of the granitic complex range from 18.2992-18.6636 for 206Pb/204Pb,from 15.5343-15.5660 for 207Pb/204Pb,and from 38.1640-38.5657 for 208Pb/204Pb For diorite-porphyrite,the isotopic ratios of 206Pb/204Pb,207Pb/204Pb and 208Pb/204Pb are 18.3919,15.5794 and 38.3566,respectively,whereas those of the ores and ore sulfides vary from 18.2275-18.3770 for 206Pb/204Pb,from 15.5555-15.5934 for 207Pb/204Pb and from 38.1318-38.3131 for 208Pb/204Pb.The results indicate that the mineralization was correlated to the formation and evolution of the granitic complex and the diorite-porphyrite.Combining with the reported data in petrologic characteristics,elemental geochemistry and chronology,conclusions can be drawn that the geodynamic settings of diagenesis and metallogenesis of this deposit were consistent with the subduction of the Izanagi oceanic plate during the Early Cretaceous.The diorite-porphyrite was formed by the emplacement of the adakitic magma triggered by partial melting of the enriched mantle,which originated from the derivative continental lithospheric mantle metasomatized by dehydration fluids from the subducting oceanic crust.The granitic complex was produced by fractional crystallization of the mixture between the adakitic magma and the high-K calc-alkaline acidic magma,which were generated by the remelting of the lower crust in the course of intraplate upwelling of the adakitic magma.The ore-bearing fluid reservoir convened in a late stage of the evolution of the mixed magma chamber.展开更多
THE Zijinshan-Bitian Cu-Au-Mo orefield is spread to north of the Shanghang County, SW Fujian.In geological structure it is located at the plunging end of NE-trending Xuanhe anticlinorium, in the NE rim ofthe NW trendi...THE Zijinshan-Bitian Cu-Au-Mo orefield is spread to north of the Shanghang County, SW Fujian.In geological structure it is located at the plunging end of NE-trending Xuanhe anticlinorium, in the NE rim ofthe NW trending Shanghang volcano-sedimentary basin. Orefield basement is composed of the Archean-Middle Proterozoic low-grade metamorphic rock formations, containing marine basic metavolcanic sequenses. Lower Cretaceous subaerial volcanic rocks of andesite-trachy andesite-rhyolite composition fill inthe volcano-sedimentary basin. Pre-mineralization granitic batholith dated 145Ma（Rb-Sr）and 157Ma（U-Pb） occupies the axial part of the plunging anticlinorium, which was regarded as crust-remelting typegranitoids. Mineralization-affiliated subvolcanic dacite porphyrite, co-volcanic granodiorite and quartzdiorite porphyrite （102.2 Ma（Rb-Sr）, Sr<sub>1</sub> = 0.708 9） belong to syntactic type in genesis and展开更多
The Naruo porphyry copper-gold deposit （hereinafter referred to as the Naruo deposit） in Tibet is a potentially ultra-large, typical gold-rich porphyry copper deposit, which was recently discovered in the Bangongco-...The Naruo porphyry copper-gold deposit （hereinafter referred to as the Naruo deposit） in Tibet is a potentially ultra-large, typical gold-rich porphyry copper deposit, which was recently discovered in the Bangongco-Nujiang metallogenic belt. This study analyzed U-Ph chronology and Hf isotopes of the ore-bearing granodiorite porphyry in the Naruo deposit using the LA-ICPMS dating technique. The results show that the weighted average age is 124.03±0.94Ma （MSWD=1.7, n=20）, and 2±6pb/23SU isocbron age is 126.2±2.7 Ma （MSWD=1.02, n=20）, both of which are within the error. The weighted average age represents the crystallization age of the granodiorite porphyry, which indicates that the ore-bearing porphyry in the Naruo deposit area was formed in the Early Cretaceous and further implies that the Neo-tethys Ocean had not been closed before 124 Ma under a typical island-arc subduction environment. The εGr（t） of zircons from the granodiorite porphyry varies from 2.14 to 9.07, with an average of 5.18, and all zircons have εRf（t） values greater than 0; 176Hf/177Hf ratio is relatively high （0.282725-0.282986）. Combined with the zircon age--Hf isotope correlation diagram, the aforementioned data indicate that the source reservoir might be a region that is mixed with depleted mantle and ancient crust, which possibly contains more materials sourced from depleted mantle. Rock-forming ages and ore-forming ages of the Duolong ore concentrate area are 120-124 Ma and 118-119 Ma, respectively, which indicate 124-118 Ma represents the main rockforming and ore-forming stage within the area. The Naruo deposit is located in the north of the Bangongco-Nujiang suture, and it yielded a zircon LA-ICPMS age of 124.03 Ma. This indicates the Bangongco-Nujiang oceanic basin subducted towards the north at about 124 Ma, and the Neo-tethys Ocean had not been closed before the middle Early Cretaceous. It is possible that the crust-mantle mixing formed the series of large and giant porphyry copper-gold deposits in the Bangongco.展开更多
基金supported by the National Natural Science Foundation of China(Nos.40472050 and 40772050)the Natural Science Foundation of Jilin Provincial Science and Technology(grant no.20080452)+1 种基金funds from the State Key Laboratory for Mineral Deposits Research,Nanjing University(2006-2005,2006- 2008)Key Laboratory of Mineral Resources, Chinese Academy of Sciences(2009-2012)
文摘An isotopic study was systemically carried out on the granitic complex,diorite-porphyrite, ores and ore minerals of the 103 Ma Xiaoxinancha gold-rich copper deposit in Jilin province to determine the geodynamic model of diagenesis and metallogenesis.Results show that the initial Nd and Sr isotopic compositions of the granitic complex are in the range of 0.70425-0.70505 for（87Sr/86Sr）i, 0.51243-0.51264 for INd,and -1.31 to ＋2.64 forεNd（t）;those of the diorite-porphyrite are in the range from 0.70438-0.70448 for（87Sr/86Sr）,,0.51259-0.51261 for INd,and ＋1.56 to ＋2.09 forεNd（t）.For ores and sulfides,the（87Sr/86Sr）i,7Nd,andεNd（t） values are in the range from 0.70440-0.70805,0.51259- 0.51279 and ＋1.72 to ＋5.56,respectively.The Pb isotopic ratios of the granitic complex range from 18.2992-18.6636 for 206Pb/204Pb,from 15.5343-15.5660 for 207Pb/204Pb,and from 38.1640-38.5657 for 208Pb/204Pb For diorite-porphyrite,the isotopic ratios of 206Pb/204Pb,207Pb/204Pb and 208Pb/204Pb are 18.3919,15.5794 and 38.3566,respectively,whereas those of the ores and ore sulfides vary from 18.2275-18.3770 for 206Pb/204Pb,from 15.5555-15.5934 for 207Pb/204Pb and from 38.1318-38.3131 for 208Pb/204Pb.The results indicate that the mineralization was correlated to the formation and evolution of the granitic complex and the diorite-porphyrite.Combining with the reported data in petrologic characteristics,elemental geochemistry and chronology,conclusions can be drawn that the geodynamic settings of diagenesis and metallogenesis of this deposit were consistent with the subduction of the Izanagi oceanic plate during the Early Cretaceous.The diorite-porphyrite was formed by the emplacement of the adakitic magma triggered by partial melting of the enriched mantle,which originated from the derivative continental lithospheric mantle metasomatized by dehydration fluids from the subducting oceanic crust.The granitic complex was produced by fractional crystallization of the mixture between the adakitic magma and the high-K calc-alkaline acidic magma,which were generated by the remelting of the lower crust in the course of intraplate upwelling of the adakitic magma.The ore-bearing fluid reservoir convened in a late stage of the evolution of the mixed magma chamber.
文摘THE Zijinshan-Bitian Cu-Au-Mo orefield is spread to north of the Shanghang County, SW Fujian.In geological structure it is located at the plunging end of NE-trending Xuanhe anticlinorium, in the NE rim ofthe NW trending Shanghang volcano-sedimentary basin. Orefield basement is composed of the Archean-Middle Proterozoic low-grade metamorphic rock formations, containing marine basic metavolcanic sequenses. Lower Cretaceous subaerial volcanic rocks of andesite-trachy andesite-rhyolite composition fill inthe volcano-sedimentary basin. Pre-mineralization granitic batholith dated 145Ma（Rb-Sr）and 157Ma（U-Pb） occupies the axial part of the plunging anticlinorium, which was regarded as crust-remelting typegranitoids. Mineralization-affiliated subvolcanic dacite porphyrite, co-volcanic granodiorite and quartzdiorite porphyrite （102.2 Ma（Rb-Sr）, Sr<sub>1</sub> = 0.708 9） belong to syntactic type in genesis and
基金financially supported by the Study on mineralization background and conditions of copper-gold in the western part of Bangongco-Nujiang metallogenic belt of Ministry of land and resources of Public industry research and special projects(201011013)Opening Foundation of Key Laboratory of Tectonic Controls on Mineralization and Hydrocarbon Accumulation,Ministry of Land and Resources(gzck2013006)Tectonic metallogeny theory development and practice team fund of Sichuan Province(13TD0008)
文摘The Naruo porphyry copper-gold deposit （hereinafter referred to as the Naruo deposit） in Tibet is a potentially ultra-large, typical gold-rich porphyry copper deposit, which was recently discovered in the Bangongco-Nujiang metallogenic belt. This study analyzed U-Ph chronology and Hf isotopes of the ore-bearing granodiorite porphyry in the Naruo deposit using the LA-ICPMS dating technique. The results show that the weighted average age is 124.03±0.94Ma （MSWD=1.7, n=20）, and 2±6pb/23SU isocbron age is 126.2±2.7 Ma （MSWD=1.02, n=20）, both of which are within the error. The weighted average age represents the crystallization age of the granodiorite porphyry, which indicates that the ore-bearing porphyry in the Naruo deposit area was formed in the Early Cretaceous and further implies that the Neo-tethys Ocean had not been closed before 124 Ma under a typical island-arc subduction environment. The εGr（t） of zircons from the granodiorite porphyry varies from 2.14 to 9.07, with an average of 5.18, and all zircons have εRf（t） values greater than 0; 176Hf/177Hf ratio is relatively high （0.282725-0.282986）. Combined with the zircon age--Hf isotope correlation diagram, the aforementioned data indicate that the source reservoir might be a region that is mixed with depleted mantle and ancient crust, which possibly contains more materials sourced from depleted mantle. Rock-forming ages and ore-forming ages of the Duolong ore concentrate area are 120-124 Ma and 118-119 Ma, respectively, which indicate 124-118 Ma represents the main rockforming and ore-forming stage within the area. The Naruo deposit is located in the north of the Bangongco-Nujiang suture, and it yielded a zircon LA-ICPMS age of 124.03 Ma. This indicates the Bangongco-Nujiang oceanic basin subducted towards the north at about 124 Ma, and the Neo-tethys Ocean had not been closed before the middle Early Cretaceous. It is possible that the crust-mantle mixing formed the series of large and giant porphyry copper-gold deposits in the Bangongco.
