青海交通社矿区碱长花岗岩锆石U-Pb年龄、岩石地球化学特征及成因探讨

交通社铌钽矿床位于阿尔金造山带,是该带近年来新发现的一个铌钽矿床。论文以该矿床为研究对象,通过开展矿床地质特征调查,利用锆石U-Pb年代学、岩石地球化学特征,探讨了与成矿密切相关的碱长花岗岩岩石成因类型及成岩成矿构造背景,探讨矿床成因。锆石LA-ICP-MS U-Pb同位素定年龄结果显示,碱长花岗岩为(453±4) Ma,属于高钾钙碱性系列,岩浆演化程度高;碱长花岗岩构造背景为后碰撞构造环境。微量元素表现为轻重稀土分馏不明显,稀土元素配分图显示,轻重稀土均相对平坦,具有明显Eu/Eu~*负异常。结合主量元素判别,同位素分析得出成岩、成矿物质为壳幔混合源。通过对比研究,结合矿床大地构造环境、成矿条件,认为交通社铌钽矿床形成于晚奥陶世,碱长花岗岩的侵入导致矿床的形成。矿床类型初步定为碱性花岗岩型铌钽矿床。

LA-ICP-MS zircon U-Pb age and petrogeochemical characteristics of Jiaotongshe area of Qinghai Province and its genesis

TheJiaotongshe niobium and tantalum deposit is located in the aljin orogenic belt, which is a newly discovered niobium and tantalum deposit in recent years. This paper takes this deposit as the research object, conducts a survey on the geological characteristics of the deposit, and USES zircon u-pb chronology and petrogeochemical characteristics to explore the genetic types of alkalifeldspathic rocks closely related to mineralization and the diagenetic and ore-forming tectonic background, so as to explore the genesis of the deposit. Zircon la-icp-ms u-pb isotope dating results show that the alkali feldspar is 453±4 Ma, and the alkali feldspar belongs to the high kali-calc-alkali series with a high degree of magma evolution. The alkali feldspar tectonic background is the post-collision tectonic environment. The trace elements showed that the light and light rare earth fractionation was not obvious, and the rare earth elements partition diagram showed that the light and light rare earth elements were relatively flat with obvious Eu/Eu* negative anomaly. Combined with the identification of the main elements, isotopic analysis shows that the diagenesis and mineralization materials are mixed sources of crust and mantle. Through comparative study, combined with the geotectonic environment and metallogenic conditions of the deposit, it is concluded that the jiaotong she niobium tantalum deposit was formed in the late ordovician, and the intrusion of alkali feldspar resulted in the formation of the deposit. The deposit type is preliminarily defined as alkali granite-type niobium tantalum deposit.