ISSN: 1003-6326
CN: 43-1239/TG

Vol. 26    No. 9    September 2016

Rock-forming mechanism of Qingshanjiao intrusion in Dongguashan copper (gold) deposit, Tongling area, Anhui province, China
Zhong-fa LIU1,2, Yong-jun SHAO1,2, Han-tao WEI1,2, Cheng WANG1,2
(1. Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitor,
Ministry of Education, Central South University, Changsha 410083, China?
2. School of Geoscience and InfoPhysics, Central South University, Changsha 410083, China
Abstract: Dongguashan deposit is a large porphyry-skarn copper (gold) deposit in Tongling ore district. The Qingshanjiao intermediate acid intrusion of Yanshanian had a direct genetic relationship with mineralization. The magma origin, rock-forming dynamic background and rock-forming process were studied, and the rock-forming mechanism of Qingshanjiao intrusion was discussed, based on geological characteristics, detailed observation of petrography and systematic investigation of petrochemistry, trace elements and REE geochemistry characteristics of Qingshanjiao intrusion. The results show that Qingshanjiao rock body belongs to high-K calc-alkaline series with higher LREE elements, Th, Rb and Sr abundance, but depleted in HREE elements, Ba, Nb and Ta. The primary magma originated from the mantle-crust mixtures which were caused by basaltic magma of mantle mixing with syenite magma of partial melting of the lower crust, and the formation environment of Qingshanjiao intrusion was emplaced in the transitional environment from compression to extension. The Harker diagram and hybrid structures of plagioclase and potassium feldspar indicate that the fractional crystallization occurred in the process of magmatic evolution. The petrochemistry, trace elements and REE geochemistry characteristics indicate that the magma was contaminated by crustal material during the rock-forming. These results suggested that the Qingshanjiao intrusion was formed by fractional crystallization and assimilation and hybridization of mantle-crust magma in the transitional environment from compression to extensional.
Key words: Qingshanjiao intrusion; geological and geochemical characteristics; rock-forming and geodynamic setting; magma derivation; rock-forming; Dongguashan copper (gold) deposit
Superintended by The China Association for Science and Technology (CAST)
Sponsored by The Nonferrous Metals Society of China (NFSOC)
Managed by Central South University (CSU)