Yanshanian magmatisms are intensive in the southern Anhui Province and can be divided into early （152-137 Ma） and late （136-122 Ma） stages. A Yanshanian granitic zone was found to crop out along Qingshan to Changg...Yanshanian magmatisms are intensive in the southern Anhui Province and can be divided into early （152-137 Ma） and late （136-122 Ma） stages. A Yanshanian granitic zone was found to crop out along Qingshan to Changgai areas in the Ttmxi district in Field investigation which has a genetic link with molybdenum multiple metal mineralization. To be a representative syenitic granite in the southern Anhui Province, the Huangshan pluton has not been found so far to have any genetic link with mineralization. Zircon LA-ICP-MS dating indicate that the four granitic bodies from the Qingshan-Changgai zone have concurrent formed ages from 140~：4 to 141~2 Ma, belonging to the Yanshanian early stage magmatism. However, the Huangshan granite is dated to be 12912 Ma, belonging to the Yanshanian late stage magmatism. The Qingshan-Changgai granites show high SiO2 and K20 contents, low P205 contents and middle A12O3 contents and are high-K calc-alkaline series metaluminum I-type granite. These rocks are characterized by enrichments in the large ion lithophile elements and light rare earth elements （REE）, depletions in the high field-strength elements, and middle degree negative anomalies of Eu, geochemical features of arc or continent crustal derived magma affinities. These rocks have 87Sr/StSr（t） ratios from 0.7120 to 0.7125,εNd（t） values from -7.24 to -4.38 and zircon εHf（t） values of -4.4 to 6.7, similar to that of the coeval ore-bearing granodiorites in the southern Anhui Province. Integrated geochemical studies indicate that the Yanshanian ore-bearing granodiorites were formed by partial melting of the Meso-Neoproterozoic accreted thickened low crust. Meanwhile, the Qingshan-Changgai granites were formed through a AFC process of plagioclase＋amphibole＋Shangxi Group of magmas that formed the ore-bearing granodiorites. The Huangshan granites are characterized by high SiOz and K2O contents, moderate Al2O3 contents, seagull shape REE distributed pattern and distinct Eu negative abnormities. Comparing with the Qingshan-Changgai granites, the Huangshan granites show more Ba, Sr, P, and Ti negative abnormities with no Nb and Ta depletions and are high-K calc-alkaline series metaluminum A-type granite, εHr（t） values of the Huangshan granites are from -6.6 to -1.2, similar to that of the early stage ore-bearing granodiorites, indicating that they were also formed by anatexis of the Meso-Neoproterozoic accreted crust, but their magma sources might be residual granulitic crust which ever underwent Yanshanian early stage I-type intermediate-acid magma extraction. Comparing studies on the two stages granites indicate that the early stage granites derived from a relative thickened low crust under a lower temperature condition. Their magma sources were Meso-Neoproterozoic accreted crust which enriched in ore-forming materials and further became more enriched through processes of magma AFC evolution. However, the late stage A-type granites originated from relative shallow crust under a higher temperature condition. Their magma source was depleted in ore-forming materials due to the early stage magma extraction and thus had weak ore-forming capacity. From early to late stage, the magmatisms tectonic setting translated from post-orogenic to anorogenic and the later corresponded to a back-arc extensional setting as increase of the slab subducted angle of the Paleo-Pacific plate.展开更多
基金supported by the State Key R&D Project of China(Grant No.2016YFC0600203)the National Natural Science Foundation of China(Grant No.41672052,41272074)
文摘Yanshanian magmatisms are intensive in the southern Anhui Province and can be divided into early （152-137 Ma） and late （136-122 Ma） stages. A Yanshanian granitic zone was found to crop out along Qingshan to Changgai areas in the Ttmxi district in Field investigation which has a genetic link with molybdenum multiple metal mineralization. To be a representative syenitic granite in the southern Anhui Province, the Huangshan pluton has not been found so far to have any genetic link with mineralization. Zircon LA-ICP-MS dating indicate that the four granitic bodies from the Qingshan-Changgai zone have concurrent formed ages from 140~：4 to 141~2 Ma, belonging to the Yanshanian early stage magmatism. However, the Huangshan granite is dated to be 12912 Ma, belonging to the Yanshanian late stage magmatism. The Qingshan-Changgai granites show high SiO2 and K20 contents, low P205 contents and middle A12O3 contents and are high-K calc-alkaline series metaluminum I-type granite. These rocks are characterized by enrichments in the large ion lithophile elements and light rare earth elements （REE）, depletions in the high field-strength elements, and middle degree negative anomalies of Eu, geochemical features of arc or continent crustal derived magma affinities. These rocks have 87Sr/StSr（t） ratios from 0.7120 to 0.7125,εNd（t） values from -7.24 to -4.38 and zircon εHf（t） values of -4.4 to 6.7, similar to that of the coeval ore-bearing granodiorites in the southern Anhui Province. Integrated geochemical studies indicate that the Yanshanian ore-bearing granodiorites were formed by partial melting of the Meso-Neoproterozoic accreted thickened low crust. Meanwhile, the Qingshan-Changgai granites were formed through a AFC process of plagioclase＋amphibole＋Shangxi Group of magmas that formed the ore-bearing granodiorites. The Huangshan granites are characterized by high SiOz and K2O contents, moderate Al2O3 contents, seagull shape REE distributed pattern and distinct Eu negative abnormities. Comparing with the Qingshan-Changgai granites, the Huangshan granites show more Ba, Sr, P, and Ti negative abnormities with no Nb and Ta depletions and are high-K calc-alkaline series metaluminum A-type granite, εHr（t） values of the Huangshan granites are from -6.6 to -1.2, similar to that of the early stage ore-bearing granodiorites, indicating that they were also formed by anatexis of the Meso-Neoproterozoic accreted crust, but their magma sources might be residual granulitic crust which ever underwent Yanshanian early stage I-type intermediate-acid magma extraction. Comparing studies on the two stages granites indicate that the early stage granites derived from a relative thickened low crust under a lower temperature condition. Their magma sources were Meso-Neoproterozoic accreted crust which enriched in ore-forming materials and further became more enriched through processes of magma AFC evolution. However, the late stage A-type granites originated from relative shallow crust under a higher temperature condition. Their magma source was depleted in ore-forming materials due to the early stage magma extraction and thus had weak ore-forming capacity. From early to late stage, the magmatisms tectonic setting translated from post-orogenic to anorogenic and the later corresponded to a back-arc extensional setting as increase of the slab subducted angle of the Paleo-Pacific plate.
文摘通过野外实地观察、样品采集及系列实验分析发现,皖南下扬子区下寒武统荷塘组页岩在研究区内分布广泛,沉积厚度大（约60~360 m）,有机质丰度高（达0.5%~7.2%）,热演化程度较高（Ro为2.0%~5.5%）,达高-过成熟阶段晚期,具有较好的生烃潜力;储集层孔隙度平均为0.716%,为游离气提供了一定的储存空间,等温吸附实验测得吸附气含量平均为0.443 cm3/g,表明研究区页岩具有较强的吸附能力。通过综合研究认为,石台—黟县—泾县—宁国一带为今后的有利勘探区,分布面积约9 100 km2.
