摘要
在野外地质调查和室内综合研究的基础上,通过对黄梅尖地区辉绿玢岩K-Ar年代学、地球化学和Sr-Nd同位素特征进行研究,探讨辉绿玢岩的形成时代、岩石成因及构造背景。K-Ar年代学研究表明,辉绿玢岩形成于~107 Ma,是早白垩世岩浆活动的产物,形成时代晚于该地区火山岩和侵入岩,与该地区铀成矿年龄基本一致;辉绿玢岩的侵入可能是该地区岩浆作用的最后一幕,铀成矿可能与辉绿玢岩具有成因联系。地球化学特征表明,辉绿玢岩富集大离子亲石元素K、Rb、U、Pb和轻稀土元素,亏损高场强元素Nb、Ta、P、Ti,具有较高的Isr值和负εNd(t)值,具有富集地幔源区特征;辉绿玢岩是在地壳伸展和岩石圈减薄的构造背景下,由俯冲交代作用形成的富集地幔部分熔融形成的,表明~107 Ma时该地区仍处于伸展构造环境下。
On the basis of field geological survey and indoor comprehensive analysis, this study discussed ore-forming age, genesis and tectonic setting of diabase porphyrite of Huangmeijian pluton in the Huangmeijian area using K-Ar chronology, geochemistry and Sr-Nd isotope geochemistry. K-Ar dating results show that the diabase porphyrite formed in ~107 Ma and should be the product of the early Cretaceous magmatic activity. The diabase porphyrite formed later than volcanic rocks and intrusive rocks in the area, but is consistent with that of U mineralization, indicating that the emplacement of diabase porphyrite was likely the last stage of magmatism and uranium mineralization may be genetically related to the diabase porphyrite. Geochemical characteristics indicate that the diabase porphyrite is rich in potassium, large ion lithophile elements(K, Rb, U and Pb) and light rare earth elements, and the loss of high field intensity elements(Nb, Ta, P and Ti), with high Isr and negative εNd(t)value, suggesting characteristic of mantle-enriched source. The diabase porphyrite was formed from partial melting of enriched mantle due to subduction metasomatism under the tectonic background of crustal extension and lithospheric thinning, indicating that the region was still in an extensional tectonic environment at ~107 Ma.
作者
杨彪
王正其
肖金根
曹达旺
YANG Biao;WANG Zheng-qi;XIAO Jin-gen;CAO Da-wang(Anhui Nucler Exploration Techonlogy Central Institute,Wuhu 241000,China;East China University of Technology,Nanchang 330013,China)
出处
《华东地质》
2020年第1期27-35,共9页
East China Geology
基金
安徽省国土资源厅“安徽省枞阳县黄梅尖及邻区铀成矿条件和找矿预测(编号:2012-K-2)”项目资助。
