Magma source and evolution law in Yueshan ore field, Anhui Province, China

LIU Zhong-fa(刘忠法)^{1, 2}, SHAO Yong-jun(邵拥军)^{1, 2}, ZHANG Jian-dong(张建东)^{1, 2}, SHU Zhi-ming(疏志明)³, ZHANG Yu(张宇)^{1, 2}

(1. Key Laboratory of Metallogenic Prediction of Nonferrous Metals of Ministry of Education (Central South University), Changsha 410083, China;
2. School of Geoscience and InfoPhysics, Central South University, Changsha 410083, China;
3. Tongling Nonferrous Metals Group Company Limited, Tongling 244000, China)

Abstract:Major elements, trace elements and sulfur, oxygen isotopic compositions of the main intrusions were studied in Yueshan area. The fact that intrusions enriched in Th and Sr, and depleted in Rb and Ba in this area, suggests that the original magma roots in alkali basalt magma of upper mantle, with deep characteristics. It can be seen that the diagenesis environments are the island arc and active continental margin areas from the lg τ to lg σ diagram of intrusions. With the increase of SiO₂, Fe₂O₃, MnO and P₂O₅ decrease, which shows that the magma of Yueshan area endured crystal fractionation of ferromanganese mineral and apatite in early evolution stage. With the further rise and evolution of magma, magma composition of calcium increased, meanwhile enriched in Zr, and depleted in Nb and Ta. This indicates that crustal component is gradually added, the assimilation and contamination occur between magma and crustal material, which includes the magma evolving, from calc-alkaline series to alkaline series. The results show that crystal fractionation, assimilation and contamination are the main evolution law of magma in this area.

Key words:lithochemistry; geochemistry; magma source; magmatic evolution; Yueshan area