用户名： 密码： 验证码：
Mesozoic Tectonic Regimes and Regional Ore-Forming Background in NE China: Constraints from Spatial and Temporal Variations of Mesozoic Volcanic Rock Associations
详细信息   
摘要
This paper summarizes geochronology and association of Mesozoic volcanic rocks and their spatial and temporal variations, with the aim of constraining evolutionary history, and ore-forming background of the circum Pacific and Mongol-Okhotsk tectonic systems in NE China. Zircon U-Pb dating results indicate that Mesozoic volcanisms in NE China can be subdivided into six stages, i.e., Late Triassic (200～228Ma), Early-Middle Jurassic (173～190Ma), Middle-Late Jurassic (158～166Ma), early Early Cretaceous (138～145Ma), late Early Cretaceous (106～133Ma), and Late Cretaceous (88～97Ma). Late Triassic volcanic rocks in NE China mainly distribute in the eastern Jilin-Heilongjiang provinces and the Lesser Xing’an-Zhangguangcai Ranges. The former consists of A-type rhyolite, the latter is composed of bimodal volcanic rocks, implying that they formed under an extensional environment after the final closure of the Paleo-Asian Ocean. Early-Middle Jurassic volcanic rocks occur in the eastern Jilin-Heilongjiang provinces, the Lesser Xing’an-Zhangguangcai Ranges, and the Erguna district. Those in the eastern Jilin- Heilongjiang provinces and the Erguna district are composed of calc-alkaline volcanic rocks, suggesting that they formed under the subductions of the Paleo-Pacific plate beneath the Eurasian continent and of the Mongol-Okhotsk oceanic plate beneath the Erguna Massif, respectively. However, those in the Lesser Xing’an-Zhangguangcai Ranges are a set of bimodal volcanic rocks, implying that they formed under an extensional environment similar to a back-arc setting of double-direction subduction. Middle-Late Jurassic and early Early Cretaceous volcanic rocks only distribute to the west of the Songliao basin, including the Great Xing’an Range and northern Hebei-western Liaoning provinces. Middle-Late Jurassic volcanic rocks consist of basaltic trachy-andesite, trachy-andesite, and trachyte, whereas early Early Cretaceous volcanic rocks are composed of A-type rhyolite and alkali rhyolite, which formed under an extensional environment related to the collapse or delamination of the thickened lower crust. The late Early Cretaceous volcanic rocks are widespread in NE China, those in the eastern Jilin-Heilongjiang provinces belong chemically to a set of calc-alkaline series, whereas those from the Songliao basin and the Great Xing’an Range are a bimodal volcanic rocks. The former marks the subduction of the Paleo-Pacific plate beneath the Eurasian continent, the latter could form under an extensional environment related to the delamination of the thickened lower crust and/or a back-arc setting. Late Cretaceous volcanic rocks mainly occur in the eastern margin of the Eurasian continent, and consist of calc-alkaline series in the continental margin and alkali basalts in intracontinent, suggesting that they formed under the subduction of the Paleo-Pacific plate. Taken together, we conclude: 1) that the subduction of the circum Pacific tectonic system beneath the Eurasian continent began in the Early Jurassic and took place in three times (Early Jurassic, late Early Cretaceous, and Late Cretaceous) during Mesozoic; the influencing spatial extent of the circum Pacific tectonic system mainly include the Songliao basin and its to east; the active continental margin and Paleo-subduction zone are favorable sites in search of porphyry ore deposits, whereas an extensional regions within intracontinent are favorable for the formation of the epithermal hydrothermal ore deposits in the eastern Jilin-Heilongjiang provinces; 2) that the Mongol-Okhotsk tectonic system experienced Early Mesozoic subduction beneath the Erguna Massif, and Middle Jurassic and early Early Cretaceous thrusting events; the influencing spatial extent of the Mongol-Okhotsk tectonic system include to west of the Songliao basin and northern margin of the North China Craton; the Early Mesozoic subduction of the Mongol-Okhotsk oceanic plate beneath the Erguna Massif is favorable for the formation of porphyry deposits, whereas the extensional environment related to the collapse or delamination of the thickened lower crust in Late Jurassic and Early Cretaceous are favorable for formation of polymetallic deposits.

© 2004-2018 中国地质图书馆版权所有 京ICP备05064691号 京公网安备11010802017129号

地址：北京市海淀区学院路29号 邮编：100083

电话：办公室：(+86 10)66554848；文献借阅、咨询服务、科技查新：66554700