山西中条山2.5 Ga TTG岩石的暖俯冲成因--来自相平衡模拟的约束  

Warm subduction origin of 2.5 Ga TTG in Zhongtiao Mountains,Shanxi:Constraints from phase equilibrium modeling.

作　　者：焦东晨 曲军峰[2] JIAO Dongchen;QU Junfeng(Research Institute of Exploration&Development,PetroChina Liaohe Oilfield Company,Panjin 124010,Liaoning,China;Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China)

机构地区：[1]中国石油辽河油田公司勘探开发研究院,辽宁盘锦124010 [2]中国地质科学院地质研究所,北京100037

出　　处：《地质通报》2024年第12期2272-2287,共16页Geological Bulletin of China

基　　金：中国地质科学院基本科研业务费专项经费(编号:JKYZD202309,YYMF201604)。

摘　　要：2.5 Ga左右地球上发生的构造机制转换,是地球演化历史中最重要的地质阶段之一,制约着地球早期大陆生长及克拉通作用的方式。TTG(奥长花岗岩、英云闪长岩、花岗闪长岩岩石组合)作为太古宙大陆地壳主体,探究其形成环境有助于更好地理解太古宙的板块构造动力学机制。但由于TTG含水熔融形成过程中的P-T条件缺失,热力学性质控制的板块构造机制无法被很好地识别。以中条山约2.5 Ga的TTG为研究对象,选取中条山文家坡约2.5 Ga的变玄武岩为源岩,对其进行TTG岩浆的定量正演模拟计算。发现在900℃/GPa地温梯度下,发生25%的含水熔融能够满足中条山约2.5 Ga TTG形成条件。据此推测,此类TTG形成于暖俯冲环境,揭示约2.5 Ga华北克拉通已经存在与地球板块生长事件对应的水平生长机制。同时部分地球化学指标的异常,也揭示构造机制已开始走向类似现代板块构造的趋势。The tectonic transition that occurred around 2.5 Ga represents one of the most significant geological events in Earth's history,shaping the early processes of continental growth and cratonization.As the dominant component of the Archean continental crust,TTGs provide valuable insights into the dynamic mechanisms of Archean plate tectonics.However,the lack of data on the pressure−temperature(P−T)conditions during the water−bearing melting processes of TTGs limits our ability to fully identify the tectonic mechanisms involved.This study investigates the 2.5 Ga TTGs in the Zhongtiao Mountains,using 2.5 Ga metabasalt from Wenjiapo as the source rock.Quantitative forward modeling of TTG magmatism revealed that 25%water−bearing melting at a geothermal gradient of 900℃/GPa satisfies the conditions for the formation of the 2.5 Ga TTGs in the Zhongtiao Mountains.The findings suggest that these TTGs formed in a warm subduction environment,indicating that by 2.5 Ga,the North China Craton had already developed a horizontal growth mechanism,consistent with global plate growth events.Additionally,anomalies in certain geochemical indicators suggest that the tectonic mechanism was beginning to transition toward a modern plate subduction environment.

关 键 词：太古宙 中条山 TTG岩石 暖俯冲 华北克拉通 

分 类 号：P534.2[天文地球—古生物学与地层学] P58[天文地球—地质学]