河南南阳独山角闪辉长岩地球化学特征及对独山玉成因的制约  

Geochemistry of evjite in Dushan(Nanyang, Henan Province): Implication for genesis of Dushan Yu

作　　者：罗勇[1] 李丹[1] 姜玉航[2,3] 李宁波[2,3] 严爽[2,3] 单强[2] 

机构地区：[1]南阳师范学院南阳市独山玉研究重点实验室,河南南阳473061 [2]中国科学院广州地球化学研究所,广东广州510640 [3]中国科学院大学,北京100049

出　　处：《地球化学》2015年第4期402-412,共11页Geochimica

基　　金：国家自然科学基金(41402068;41301443);河南省高等学校重点科研项目(15A170004);南阳师范学院高层次人才科研启动项目(ZX201300970337);南阳师范学院教学研究项目(2014-14)

摘　　要：独山岩体位于河南省南阳市北郊，出露岩石主要以角闪辉长岩为主，中国四大名玉之一的“独山玉”呈透镜体或脉体产在岩体中，并明显受构造裂隙的控制。本文对独山角闪辉长岩进行了系统的岩相学、主元素、微量元素研究。独山角闪辉长岩为亚碱性岩石，低SiO2、高Mg^#、贫碱；明显富集大离子亲石元素K、Rb、Sr、Pb，亏损高场强元素Th、Nb、Ta、Zr、Hf,反映源区物质可能受到了流体交代作用。独山角闪辉长岩可能形成于板块汇聚边缘，源区可能为受俯冲流体交代的富集石榴石．尖晶石橄榄岩地幔源区，是其经历1％～3％部分熔融的产物。独山玉可能是富水的独山角闪辉长岩在区域动力变质作用下的产物，在动力变质过程中形成了由重结晶的亚颗粒斜长石和石英及晶形完好的黝帘石组成的透镜体和脉体的独山玉。Dushan massif, located in the northern suburb of Nanyang City, Henan Province, consists mainly of evjite. As one of the four most famous youstones in China, ＂Dushan Yu＂ occurs in form of lenses or veins in the massif, which is apparently under the control of tectonic fractures in the region. This paper report results of petrologic, bulk-rock geochemical data for the Dushan evjite. Dushan evjite, mainly sub-alkaline basalts, is characterized by low SiO2, high Mg^#, and poor alkaline, but is significantly enriched in large ion lithopbile elements （LILEs） like K, Rb, Sr, Pb, depleted in high field strength elements （HFSEs） such as Th, Nb, Ta, Zr, Hf. These results reflect that the source substance may have been formed from fluid metasomatism. Dushan evjite may be formed at the edge of plate convergence, originated from a garnet-spinel-rich peridotite mantle source undergoing metasomatism of subducting fluid and 1%-3% partial melting. Dushan Yu may be resuled from regional dynamic metamorphism of water-rich evjite, as it occur in forms of lenses and veins, and consists of recrystallized sub-particles plagioclase and quartz and well crystallized zoisite in the process of dynamic metamorphism.

关 键 词：角闪辉长岩 主元素 微量元素 独山玉 

分 类 号：P595[天文地球—地球化学] P59[天文地球—地质学]