藏北中—新生代花岗岩与金矿成矿

The relationship between the granites of Messozoic and Cenozoic eras and gold mineralization in North Tibet

藏北地区中、新生代岩浆活动强烈,花岗岩成岩机制复杂。金矿时空分布特征与岩体密切相关,初步研究表明,与金矿成矿有关的花岗岩为火山弧环境下的同熔型花岗岩,结合同位素研究,认为该区成矿物质可能来源于壳幔过渡带或基底。花岗岩主量元素,Rb、Sr、O同位素研究发现,随成岩时代变化,岩体成岩构造环境、物质来源、金矿化强度呈周期性(脉动性)变化。金矿成矿作用与岩浆活动之间表现出统一性和周期性的变化特征,是和本区大地构造演化密切相关的。

The magmatic activity of Messozoic and Cenozoic eras is very strong in North Tibet, in which the diagenetic mechanism of granite is complicated. The spacetime distribution features have close relation with the ore bodies. The primary study shows that the granites that relate to gold mineralizations belong to the syntactic granites that under the volcanic arc environment. Combining the study of isotope,the oreforming materials in this area may be from the crustmantle transition belt or basement. According to the major element and Rb, Sr and O isotopes study of the granite, its found that with the changing of diagenetic periods of the rockbody,the diagenetic structure setting, material resources, gold mineralization intensity of ore bodies appeared periodical (pulsation) variation. The features of unified and periodical variation between gold mineralization and magmatic activity are closely related to the evolution of tectonic structure of the area .