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作 者:张达[1,2] 吴淦国[1,2] 狄永军[1] 余心起[1] 彭润民[1,2] 黄火剑[1]
机构地区:[1]中国地质大学地质过程与矿产资源国家重点实验室,北京100083 [2]中国地质大学岩石圈构造,深部过程及探测技术教育部重点实验室,北京100083
出 处:《地质力学学报》2009年第1期20-35,共16页Journal of Geomechanics
基 金:国家自然科学基金项目(40372050);地质调查项目"武夷山成矿带铜多金属成矿规律研究"(1212010533105);"武夷山成矿带中生代推覆构造与铜多金属找矿方向研究"项目(1212010813064)
摘 要:尤溪梅仙峰岩铅锌银矿床位于政和-德化前寒武纪变质分布区的南端,处于北东向丽水-海丰断裂东侧闽东火山断拗带的次级寿宁-华安基底隆起带内。峰岩矿床的含矿岩系主要为上元古界马面山群东岩组(Pt3dy)。铅锌银矿体具层控特点。岩石学及地球化学研究表明赋矿地层东岩组为以绿片岩为主的一套古火山沉积建造。绿片岩的原岩为玄武岩类,变粒岩主要为英安岩及流纹岩。玄武岩浆的形成可能和板块俯冲相关。矿床地球化学研究表明矿床存在多次成矿作用和多种硫源。铅同位素组成与演化表明从幔源至造山带和上地壳不同的铅源均有混入,演化趋势较明显,并显示多次地质事件叠加特点。金属硫化物的稀土分布型式都表现为一定程度的右倾斜,轻重稀土分异显著。微量元素相对于MORB均有不同程度的亏损和富集。高场强元素(HFSE:Nb、Ta、Zr、Hf)表现为明显的负异常,具较强烈的亏损;而Pb、Rb和Ba等元素相对富集。东岩组变质火山岩也表现为明显的高场强元素的亏损及低场强元素的富集,显示出典型和俯冲有关的岛弧岩浆的特征,表明矿床与东岩组火山岩都形成于俯冲背景下的岛弧环境。Pb-Zn-Ag ore deposit in Meixian, Youxi County is located at the south of the Zhenghe-Dehua pre-Cambrian metamorphic area, and geologically situated at Shouning-Hua'an sub-basement uplift zone in Eastern Fujian volcanic depression belt, east of the NE-striking Lishui-Haifeng fault. The ore-bearing beds of Fengyan ore deposit is mainly the Upper Proterozoie Dongyan Fomation of Mamianshan Group (Pt3dy). The Pb-Zn-Ag ore bodies are of strata bound type. Petrology and geochemistry studies show that the ore-bearing Dongyan Formation is a paleo-volcanic sedimentary formation dominated by greenshists. The formation of the basaltic magma may be related to the slab subduction. The original rocks of the greenshists are basaltic rocks, and granulites are mainly dacite and rhyolite. Geochemical study of ore deposit reveals that the ore deposit is characterized by multiple ore-forming processes and various kinds of sulfur sources. The composition and evolution of Pb isotopes show that different Pb sources from mantle to orogenic belt and upper crust are intermingled. The evolvement is of clear trend and demonstrates a superposition of multiple geological events. The REE pattern of metal sulfides shows a down-to-right slope with remarkable differentiation between LREE and HREE. Compared to MORB, the different trace elements are depleted and enriched to different degrees. High field strength dements (HFSE: Nb, Ta, Zr, Hf) show distinct negative anomaly and are strongly depleted while Pb, Rb and Ba are relatively enriched. Metavolcanics in the Dongyan Formation, with the same trend of HFSE depletion and the enrichment of LFSE, displays typical features of arc-magma related to subduction and indicates that the ore deposit and the Dongyan vocanics were formed under the arc environment with subduetion background.
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