陕南铁船山岩体的地球化学特征、成因及其形成的构造环境

扬子克拉通北缘的铁船山岩体形成于新元古代，其岩石类型为霓石－钠铁门石花岗岩，岩石富碱质、Ｓｔ、Ｆｅ、ＲＥＥ和高场强元素，而贫Ａｌ、Ｃａ、Ｍｇ、Ｓｒ、Ｂａ、Ｃｏ、Ｎｉ等组分，δＥｕ＝０．２０，Ａ／ＫＮＣ＝０．８５，Ｋ２Ｏ＋Ｎａ２Ｏ／Ａｌ２Ｏ３＝１．０９，Ａ·Ｒ＝９．２８，岩石属典型的Ａ型花岗岩，Ｎｄ、Ｓｒ和Ｏ同位素示踪反映其成岩物质来自于壳幔混合源区。根据区域地质背景的综合分析，岩体形成于活动陆缘的张裂构造环境，属活动板块边缘拉张型花岗岩。

GEOCHEMICAL CHARACTERISTICS, GENESIS AND TECTONIC ENVIRONMENT OF THE TIECHUANSHAN PLUTON IN THE SOUTHERN SHAANXI PROVINCE

The Tiechuanshan pluton at the northern margin of the Yangtze craton formed in newProterozic. The rocks of the pluton, which rock-type is aegirine-augite granite, are richerin K2O+Na2O, SiO2, ΣFeO, REE, Zr, Th, Nb, Ta and poorer in A12O,, CaO, MgO,Sr, Ba, Co, Ni, with δEu=0. 20, A/KNC=0. 85, K2O+Na2O/Al2O3=1.09 and A· R= 9. 28. Consequently, the rocks are typical A-type granites. According to the compositionof Nd, Sr and O isotopes, the pluton may be derived from a crust-mantle mixture source.The A-type granites formed in the extensional tectonic setting of active continental marginthrough the analysis of regional geological setting. Thus,tectonic type of the rocks belongsto the extension--type granites at the active plate margin.