胶东郭城地区脉岩类岩石地球化学特征及成岩构造背景  

Geochemstry and Tectonic Setting of Dikes in the Guocheng Area, Jiaodong Peninsula

作　　者：谭俊[1] 魏俊浩[1] 杨春福 冯波 谭文娟[1] 郭大招[1] 

机构地区：[1]中国地质大学资源学院,武汉430074 [2]山东烟台鑫泰黄金矿业有限责任公司,265147

出　　处：《地质学报》2006年第8期1177-1188,共12页Acta Geologica Sinica

基　　金：教育部博士点基金项目(编号20040491502)资助的成果。

摘　　要：胶东海阳郭城地区高密度、高频率产出多种脉岩类岩石,主要包括辉绿岩(βμ)、煌斑岩(χ)、闪长岩(δ)、闪长玢岩(δμ)、花岗斑岩(νπ)、正长斑岩(ξπ)等,且脉岩与金矿密切伴生。为了探讨该区脉岩的成因、源区性质及成岩构造背景,本文通过岩石学和地球化学研究表明,该区脉岩总体属于钾质钙碱性系列,高Mg、Fe、Al,低Ti,来自深部同一岩浆源区,富集LILE和LREE,相对亏损HFSE,为弥散状角闪石相橄榄岩富集地幔部分熔融作用(9.52%)的产物。成岩过程中岩浆经历了橄榄石、单斜辉石、角闪石等暗色矿物以及少量斜长石的分离结晶作用,岩浆侵位过程中没有受到地壳物质的混染。脉岩形成于大陆板内环境,同时具有大陆弧钙碱性玄武岩的地球化学特征,暗示了在构造背景上与太平洋板块的俯冲作用及晚侏罗世至早白垩世华北地块岩石圈的区域性伸展—减薄机制有关,可能与郯庐断裂带在该时期的左行走滑引张关系更为密切。Highly dense and frequent dikes are temporally and spatially associated with gold deposits in the Guocheng area in the Jiaodong Peninsula, which mostly include diabase, lamprophyre, diorite, diorite-porphyrite, granite-porphyrite and syenite-porphyrite. In order to investigate their genesis, source characteristics and tectonic background of diagenesis, the petrology and geochemistry are reported in this paper. In terms of major elements, the dikes are attributed to the potassic calc-alkaline series as a whole. They possess high Mg, Fe, Al and low Ti contents. The dikes are rich in LILE and LREE, and relatively depleted in HFSE, suggesting a production of partial fusion （9. 52%） of disseminated amphibole peridotite of enriched mantle. The magma might undergo fractional crystallization of olivine, clinopyroxene, hornblende and weak plagioclase during the diagenesis process, which however is not obviously contaminated by crust materials in the emplacement process. Meanwhile, the dikes are formed in intraplate environment but possess the geochemical features of continental marginal arc calc-alkaline basalt, implying their relationship to the Pacific Plate subduction and Late JurassicEarly Cretaceous thinning event in the lithosphere of the North China Block, especially the sinistral strike-slip extension of the Tanlu fault zone.

关 键 词：脉岩 地球化学 富集地幔 构造背景 胶东 

分 类 号：P581[天文地球—岩石学] P584[天文地球—地质学]