浙西桐村斑岩型钼(铜)矿床与德兴斑岩铜矿岩浆岩对比研究

桐村地区与德兴矿区岩石系列相似,为高钾钙碱性系列;在岩石结构上,桐村地区花岗闪长岩为似斑状结构,德兴矿区花岗闪长斑岩为斑状结构。两者均为钙碱—碱质镁质I型花岗岩。桐村岩石富Si和K,A/CNK和K/(K+Na)值均小于德兴岩石。微量元素、同位素及岩石学特征表明桐村地区的物质来源以壳源为主,而德兴地区为有大量幔源物质参与的壳幔混合型,其原因可能与两区不同的构造位置有关。中晚侏罗世时,太平洋板块西向俯冲,下插板片发生部分熔融形成的岩浆与岩石圈地幔楔发生作用从而形成斑岩岩浆是桐村和德兴地区可能的成因模式。桐村矿床含矿斑岩的氧逸度、演化程度和地壳混染程度均较德兴斑岩铜矿高。对于同时代、近距离的岩浆岩形成如此规模悬殊的矿床还有许多问题值得研究和思考。

A Comparative Study of Granites in Tongcun Porphyry Molybdenum-Copper Deposit in West of Zhejiang Province and Dexing Porphyriry Copper Deposit

Both granites of Tongcun and Dexing district are high K calc alkaline, magnesian I type granites. Texture of Tongcun granodiorite is porphyaceous while Dexing granodiorite porphyry is porphyritic. Granites in Tingcun district is characterized to be rich in Si and K, the ratio of A/CNK and K/(K+Na) is less than rocks in Dexing district. The features of trace elements, isotopes and petrolography of Tongcun and Dexing granites suggest that the origin of the first be mainly crust while the latter be crust mantle thrived and the reason might be connected with their distinct tectonic settings. It is concluded that Tingcun and Dexing porphyries were emplaced in a continental arc setting coupled with westward subduction of the palaeopacific plate. Partial melting involved the subducted slab, with generated melts interacting with the lithospheric mantle wedge during medium to late Jurassic. The fo2, evolution degree and contamination degree of Tongcun ore bearing porphyry is higher than Dexing porphyry. Further study of the reason of distinct scale in coetaneous deposits in such a short distance is worthy studying.