摘要
对松潘-甘孜北部岗龙地区的花岗岩岩株进行了详细的岩石地球化学、锆石U-Pb年代学和锆石Hf同位素的研究,探讨了其成因。结果表明,锆石LA-ICP-MS测年年龄分别为（207.5±2）,（209±2.4）Ma,形成时期为晚三叠世。SiO2质量分数较高,高K低Na。Al2O3质量分数高,为强过铝质。轻稀土元素富集,具明显的Eu负异常,亏损Ba、Nb、Ta、Sr、Ti,富集Rb、Th、Pb、Hf等,具有S型花岗岩特征,锆石εHf（t）值在-18.6~4.7之间,推测为三叠纪浊流沉积经部分熔融结晶而成,并受到地幔物质的混染,通过锆石饱和温度,推测幔源岩浆为岩体的形成提供了热源。结合松潘-甘孜造山带区域地质背景及岩浆演化规律分析表明,松潘-甘孜造山带印支期花岗岩形成于地壳拆沉作用,岗龙地区S型花岗岩是中地壳重融作用形成。
The paper studies geochemical composition and zircon U-Pb chronological characteristics of granite in Ganlong district,north of Songpan-Ganzi fold belt（SGFB）.The ages of the U-Pb zircons LA-ICPMS dating（207.5±2）Ma and（209±2.4）Ma,show that the emplaced ages are later Triassic.These granites are high K and low Na,with high SiO2 and hence are strongly peraluminous granitoids with high Al2O3.The granites are light REE enriched with negative europium,Ba,Nb,Ta,Sr and Ti deplecation and Rb,Th,Pb and Hf enriched.Their characteristics are compatible with those of S-type granites.εHf（t）value is-18.6-4.7.The geochemecial and Hf isoplote suggest that the granites were derived from partial melting of the turbidite deposit of Triassic and were influenced by the mantle.According to the combined analysis of geological background,regional tectono-magmatic events and magmatism composition,the Indosinian granite in Songpan-Ganzi fold belt should be probably generated by the delamination of lower crust,while the delamination has resulted in partial melting at different levels of crust.The S-type granites in the Songpan-Ganzi fold belt is thus the product of the partial melting of the middle-lower crust.
出处
《地质科技情报》
CAS
CSCD
北大核心
2016年第2期129-139,共11页
Geological Science and Technology Information
基金
中国地质调查局项目"青海省甘德县青珍矿产远景调查"(12120113031400)
