ZHANG Qing-wen1, 2, ZHU Dan1, XU Ying-kui1, 2
(1. State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China;
2. University of Chinese Academy of Sciences, Beijing 100049, China)
Abstract: Crustal melting is dominated by the factors of rock type, water content and decompression melting. It requires a high geothermal gradient within the crust and its heat source is therefore the key to understanding the crustal anatexis and generation of silicic magma. This paper reviews studies on crustal melting and tries to summarize the proposed heat source that induces crustal anatexis. In most cases, heat has been believed to originate from the hot, mantle-derived mafic magma underplated into the crust or at the Mohorovic Discontinuity level. However, the underplating model, to some extent supported by certain evidence, has difficulty explaining the irrelevant occurrence between massive silicic and mafic magmatism and the fact that the genesis of S-type granite magma is closely related to melting of the upper crust. Moreover, extant results of underplating simulation overestimate the potential effect of basaltic magma intrusion on the crustal melting. A hypothesis is proposed as an alternative explanation of the large-scale crustal melting: the combined effects of the depth-dependent lithospheric extension and crustal thickness compensation of the rapidly-deposited sediments leads to an abnormally high geothermal gradient inside the crust, resulting in extensive melting of the upper crust consisting of meta-sedimentary rock and the generation of S-type silicic magma.
Keywords: crustal melting; intraplate setting; underplating; depth-dependent extension; depositional compensation
E-mail: zhudan@vip.gyig.ac.cn
ACTA MINERALOGICA SINICA Vol. 35, No. 1, 2015, Page 44-50
