科研之友
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摘要
We investigate the role of crustal architectures playing in controlling the genesis and nature of supergiant Jiaodong orogenic gold system via seismic imaging. We deployed an NWW-SEE-trending broadband seismic linear array traversing the province to construct a shear wave velocity (VS) transect based on ambient noise tomography. Our crustal VS transect reveals a prominent low velocity zone (LVZ) at 12-20 km depths across the whole province and high VS anomalies at 8-12 km depths underneath the western part that hosts most of the ore tonnage. We interpret the former as a hydrothermal alteration zone related to mineralization and the latter as a crustal component containing large amounts of mafic rocks (e.g., amphibolites). In addition, a listric fault system and a strike-slip fault system are imaged in the western and eastern parts of the province, respectively. Combining features of crustal velocities with regional geological observations that ores are tempo-spatially associated with mafic dikes, we propose a model of gold metallogenic processes. In this model, ponding and degassing of the mafic magmas led to the formation of a hydrothermal alteration LVZ in the middle crust prior to mineralization. Later, auriferous fluid was released from this intra-crustal hydrothermal alteration zone as it was heated by upwelling asthenosphere. The ore fluid ascending along the listric fault system possibly leached extra gold from the upper-crustal amphibolites. Then, the gold-rich fluid migrated up along different fault systems, leading to the disseminated-veinlet mineralization with great gold endowment in the western listric fault system and the quartz-vein type mineralization with relatively small ore tonnage in the eastern strike-slip fault system.
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单位Chinese Academy of Science; Guilin University Of Technology; Graduate University of Chinese Academy of Sciences
