科研之友
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摘要
porphyry copper deposits in the Middle-Lower Yangtze River has been controversial for a long time. This paper aims to track the source of ore-bearing porphyries and associated mafic xenoliths by using high-precision Cu isotopic analysis of a series of Mesozoic plutons in the Ningzhen area. The results show a wide range of 865 Cu of Anjishan dioritic porphyries from - 0. 13 parts per thousand to 0. 36 parts per thousand and a homogeneous Cu isotopic composition of the gabbro xenoliths from 0. 14 parts per thousand to 0. 19 parts per thousand. delta(65) Cu of the Tongshan porphyries are in the range of 0. 03 parts per thousand to 0. 36 parts per thousand, and gabbro xenoliths are from 0. 10 parts per thousand to 0. 20 parts per thousand. delta(65) Cu of granodiorite in Xiangshan pluton is 0. 20 parts per thousand /- 0. 06 parts per thousand and delta(65) Cu value of the gabbro xenolith is 0. 16 parts per thousand /- 0. 06 parts per thousand. Overall, delta(65) Cu values of porphyries from the three plutons exhibit a relatively large range; however, 865 Cu of gabbro xenoliths cluster between 0. 1 parts per thousand and 0. 2 parts per thousand, with an average value of 0. 15 parts per thousand /- 0. 05 parts per thousand, consistent with the mantle value ( 0. 07 parts per thousand /- 0. 10 parts per thousand). Previous studies show that the ore-bearing porphyries in Ningzhen have high MgO, high Mg-# values and low radiogenic Pb isotopic compositions, and that ancient lower crustal rocks commonly show variable Cu isotopic compositions. Thus, the genesis of the ore-bearing porphyries and the origin of copper in these deposits might be best explained by magma mixing between the magmas derived from metasomatized mantle and melts originated from old lower continental crust.
- 出版日期2015-7
- 单位中国地质大学（北京）; 合肥工业大学
