The Jiangla＇angzong granite in the northern part of the Central Lhasa Terrane is composed of syenogranite and adamellite. LA-ICP-MS zircon U-Pb analyses suggest that syenogranite has a weighted mean 2±6pb/23SU a...The Jiangla＇angzong granite in the northern part of the Central Lhasa Terrane is composed of syenogranite and adamellite. LA-ICP-MS zircon U-Pb analyses suggest that syenogranite has a weighted mean 2±6pb/23SU age of 86±1 Ma （mean square weighted deviation=0.37）, which is in accordance with the muscovite Ar-Ar age （85±1 Ma） of Cu-Au ore-bearing skarns and the zircon U-Pb age （84±1 Ma） of adamellite. This suggests that the Jiangla＇angzong magmatism and Cu-Au mineralization events took place during the Late Cretaceous. The granite contains hornblende, biotite, and pyroxene, and does not contain Al-bearing minerals, such as muscovite, cordierite, and garnet. It has high contents of SiO2 （65.10 -70.91wt%）, K20 （3.44-5.17wt%）, and total K20＋Na20 （7.13-8.15wt%）, and moderate contents of A12Oa （14.14-16.45wt%） and CaO （2.33-4.11wt%）, with a Reitman index （δ43） of 2.18 to 2.33, and A/ CNK values of 0.88 to 1.02. The P205 contents show a negative correlation with SiO2, whereas Pb contents show a positive correlation with SiO2. Th and Y contents are relatively low and show a negative correlation with the Rb contents. These characteristics suggest that the Jiangla＇angzong granite is a high K calc-alkaline metaluminous I-type granite. It is enriched in light rare earth elements （LREE） and large ion lithofile elements （LILE）, and depleted in heavy rare earth elements （HREE） and high field strength elements （HFSE）, with LREE/HREE ratios of 11.7 to 18.1. The granite has negative Eu anomalies of 0.58 to 0.94 without obvious Ce anomalies （δCe=l.00-1.04）. The relatively low initial a7Sr/a6Sr ratios of 0.7106 to 0.7179, positive ε±nt（t） values of 1.0 to 4.1, and two-stage Hf model ages （TDM2） ranging from 889 Ma to 1082 Ma, These geochemical features indicate that the granite derived from a juvenile crust. The （143Nd/144Nd）t values from the Jiangla＇angzong granite range from 0.5121 to 0.5123, its eNd（t） values range from -10.17 to -6.10, its �展开更多
A geochronological study of zircon U-Pb on the volcanic rocks from the stratotype section of the Qingshan Group within the Jiaozhou Basin, eastern Shandong Province, is presented. The zircons were analyzed using the m...A geochronological study of zircon U-Pb on the volcanic rocks from the stratotype section of the Qingshan Group within the Jiaozhou Basin, eastern Shandong Province, is presented. The zircons were analyzed using the method of in situ ablation of a 193 nm excimer laser system coupled with an up to date ICP-MS system. Among the three formations of the Qingshan Group, zircons recovered from the lowest part of the Houkuang Fm. were dated at 106±2 Ma (95% confidence, the same below), whereas those from the lower and upper parts of the Shiqianzhuang Fm. were given ages of 105±4 Ma and 98±1 Ma, respectively. A spatially decreasing trend for the Mesozoic magmatic timing from west to east in the province is observed through comparing the data of this study with those by previous works on the Qingshan volcanic lavas occurring at western Shandong and within the Yishu fault zone. The Qingshan volcanic rocks are constituent of the 'Shoshonite Province' in East China. Exposed at most provinces of central East China along the Tan-Lu fault and the Yangtze fault zones, these volcanic suites are characterized by shoshonite and high-K calcalkalic rocks in lithology and thought to be correlated with the partial melting of continental mantle in genesis. It is also shown that the Qingshan potassic volcanic suite from eastern Shandong basins is distinctly younger than those from other ar-eas of the shoshonite province. By contrary, ages of the Mesozoic to Cenozoic alkaline basalts, sourced by asthenospheric mantle, from both northern Huaiyan basin and northern Dabie belt along the Tan-Lu fault zone and from the Ningwu, Lishui and Luzong basins along the Yangtze fault zone are observably older than those occurring within eastern Shandong. The revealed temporal and spatial patterns in magmatism for the two types of volcanic suites make an important geochronological con-straint on the Mesozoic to Cenozoic dynamic evolution model of the subcontinental lithosphere in East China.展开更多
Paleoproterozoic potassic granitoids in the southern Sushui Complex from the Zhongtiao Mountains yielded SHRIMP zircon U-Pb ages of 1968-1944 Ma. Lithologically, the potassic granitoid series consists chiefly of monzo...Paleoproterozoic potassic granitoids in the southern Sushui Complex from the Zhongtiao Mountains yielded SHRIMP zircon U-Pb ages of 1968-1944 Ma. Lithologically, the potassic granitoid series consists chiefly of monzodiorite, quartz monzonite and syenogranite. Their trace elements and Sm-Nd isotope characteristics indicate that they were derived from partial melting of Archean TTG rocks in an overthickened continental crust. Petrogenesis of this potassic granitoid series implies a collisional environment within the Trans-North China Orogen in the Paleoproterozoic, which supports a tectonic model of Eastern and Western Continental Blocks being amalgamated in the Paleoproterozoic.展开更多
基金financially supported by the National Key Research and Development Program of China (Grant No.2016YFC0600308, SQ2018YFC060162)the China Geological Survey Project (Grant No.DD20160015,DD20160026)+1 种基金the International Scientific Plan of the Qinghai Xizang (Tibet) Plateau of Chengdu Center, China Geological Surveythe Natural Science Foundation of China (Grant No.41702080, 41702086)
文摘The Jiangla＇angzong granite in the northern part of the Central Lhasa Terrane is composed of syenogranite and adamellite. LA-ICP-MS zircon U-Pb analyses suggest that syenogranite has a weighted mean 2±6pb/23SU age of 86±1 Ma （mean square weighted deviation=0.37）, which is in accordance with the muscovite Ar-Ar age （85±1 Ma） of Cu-Au ore-bearing skarns and the zircon U-Pb age （84±1 Ma） of adamellite. This suggests that the Jiangla＇angzong magmatism and Cu-Au mineralization events took place during the Late Cretaceous. The granite contains hornblende, biotite, and pyroxene, and does not contain Al-bearing minerals, such as muscovite, cordierite, and garnet. It has high contents of SiO2 （65.10 -70.91wt%）, K20 （3.44-5.17wt%）, and total K20＋Na20 （7.13-8.15wt%）, and moderate contents of A12Oa （14.14-16.45wt%） and CaO （2.33-4.11wt%）, with a Reitman index （δ43） of 2.18 to 2.33, and A/ CNK values of 0.88 to 1.02. The P205 contents show a negative correlation with SiO2, whereas Pb contents show a positive correlation with SiO2. Th and Y contents are relatively low and show a negative correlation with the Rb contents. These characteristics suggest that the Jiangla＇angzong granite is a high K calc-alkaline metaluminous I-type granite. It is enriched in light rare earth elements （LREE） and large ion lithofile elements （LILE）, and depleted in heavy rare earth elements （HREE） and high field strength elements （HFSE）, with LREE/HREE ratios of 11.7 to 18.1. The granite has negative Eu anomalies of 0.58 to 0.94 without obvious Ce anomalies （δCe=l.00-1.04）. The relatively low initial a7Sr/a6Sr ratios of 0.7106 to 0.7179, positive ε±nt（t） values of 1.0 to 4.1, and two-stage Hf model ages （TDM2） ranging from 889 Ma to 1082 Ma, These geochemical features indicate that the granite derived from a juvenile crust. The （143Nd/144Nd）t values from the Jiangla＇angzong granite range from 0.5121 to 0.5123, its eNd（t） values range from -10.17 to -6.10, its �
基金the National Natural Science Foundation of China (Grant No. 40133020)Innovation Term Grant of Ministry of Education of China
文摘A geochronological study of zircon U-Pb on the volcanic rocks from the stratotype section of the Qingshan Group within the Jiaozhou Basin, eastern Shandong Province, is presented. The zircons were analyzed using the method of in situ ablation of a 193 nm excimer laser system coupled with an up to date ICP-MS system. Among the three formations of the Qingshan Group, zircons recovered from the lowest part of the Houkuang Fm. were dated at 106±2 Ma (95% confidence, the same below), whereas those from the lower and upper parts of the Shiqianzhuang Fm. were given ages of 105±4 Ma and 98±1 Ma, respectively. A spatially decreasing trend for the Mesozoic magmatic timing from west to east in the province is observed through comparing the data of this study with those by previous works on the Qingshan volcanic lavas occurring at western Shandong and within the Yishu fault zone. The Qingshan volcanic rocks are constituent of the 'Shoshonite Province' in East China. Exposed at most provinces of central East China along the Tan-Lu fault and the Yangtze fault zones, these volcanic suites are characterized by shoshonite and high-K calcalkalic rocks in lithology and thought to be correlated with the partial melting of continental mantle in genesis. It is also shown that the Qingshan potassic volcanic suite from eastern Shandong basins is distinctly younger than those from other ar-eas of the shoshonite province. By contrary, ages of the Mesozoic to Cenozoic alkaline basalts, sourced by asthenospheric mantle, from both northern Huaiyan basin and northern Dabie belt along the Tan-Lu fault zone and from the Ningwu, Lishui and Luzong basins along the Yangtze fault zone are observably older than those occurring within eastern Shandong. The revealed temporal and spatial patterns in magmatism for the two types of volcanic suites make an important geochronological con-straint on the Mesozoic to Cenozoic dynamic evolution model of the subcontinental lithosphere in East China.
基金This study was financially supported by the National Natural Science Foundation of China （Grant Nos. 40412012035 and 40511140503）.
文摘Paleoproterozoic potassic granitoids in the southern Sushui Complex from the Zhongtiao Mountains yielded SHRIMP zircon U-Pb ages of 1968-1944 Ma. Lithologically, the potassic granitoid series consists chiefly of monzodiorite, quartz monzonite and syenogranite. Their trace elements and Sm-Nd isotope characteristics indicate that they were derived from partial melting of Archean TTG rocks in an overthickened continental crust. Petrogenesis of this potassic granitoid series implies a collisional environment within the Trans-North China Orogen in the Paleoproterozoic, which supports a tectonic model of Eastern and Western Continental Blocks being amalgamated in the Paleoproterozoic.
