华南中生代陆内成矿作用

Mesozoic intraplate metallogenesis in South China

陆内成矿机制是全球性科学难题。华南陆块中生代成矿大爆发,成矿作用远离活动大陆边缘,形成西部金锑铅锌低温成矿省和东部钨锡多金属高温成矿省,是研究陆内成矿的理想场所。因为空间上的分离,两个成矿省长期被认为是互为独立的体系。研究发现,西部低温成矿(230~200 Ma、160~130 Ma)与东部高温成矿时代一致并显示类似的地球化学指纹,印支期陆内造山和燕山期软流圈上涌是其共有成矿驱动机制,两个成矿省是具有成因联系的整体,共同构成面状展布的巨型多金属陆内成矿区;成矿后华南从西向东剥蚀程度的增强控制了目前近地表矿西部低温、东部高温的空间分布格局,低温成矿省东部区域的深部可能存在高温钨锡多金属矿床。在此基础上,建立了定位于陆内岩石圈先存薄弱区、陆壳供给矿源、高低温矿并重、成矿面状展布从而明显区别于板块边缘成矿机制的华南陆内成矿新理论。

Intraplate metallogenesis is a significant global scientific issue.The South China block is renowned for its large-scale mineralization occurring far away from active continental margins during the Mesozoic.It formed a low-temperature metallogenic province of gold,antimony,lead,and zinc deposits in the west(Yangtze block)and a high-temperature metallogenic province of tungsten-tin polymetallic deposits in the east(Cathaysia block),making it an ideal natural laboratory for intraplate metallogenesis studies.The two metallogenic provinces of South China have long been considered distinct systems due to their spatial separation.However,our research revealed that the low-temperature mineralization in the west(230200 Ma and 160130 Ma)occurred simultaneously with the high-temperature mineralization in the east,and has similar geochemical fingerprints to the latter.Both types of mineralization were probably driven by the Indosinian intracontinental orogeny and Yanshanian asthenosphere upwelling beneath South China.Therefore,there is a genetic linkage between the two metallogenic provinces,and together they constitute a giant polymetallic domain spreading planarly under intraplate setting.The current distribution status of the low-and high-temperature mineralization types in the west and east is controlled by the eastward increase of denudation degree in South China after ore formation.It is predicted that there may exist high-temperature W-Sn polymetallic deposits beneath the eastern region of the low-temperature metallogenic province.A new intraplate metallogenesis model for South China was established.The significant features of the new model include metallogenesis occurring within preexisting weakness zones of lithosphere,continental crust serving as sources for metallogenic elements,and coexistence of high-and low-temperature mineralization exhibiting a distinct planar distribution.The model differs from the metallogenic mechanism in continental plate margins.