西南天山阿克牙孜下游地区变质岩的演化:来自碳质拉曼光谱温度计的启示

西南天山造山带是塔里木板块和伊犁-中天山板块聚合碰撞的产物，经历了长期复杂的演化.伊犁-中天山陆块南缘的变质作用研究对于揭示西南天山的地质演化历史具有重要意义.这一地区变质岩分布广泛，但目前的变质作用研究主要集中于木扎尔特的高级变质岩，位于同一构造带上其他变质岩的演化和分布特点缺少详细的研究，尚不清楚它们是作为高温变质带的一部分还是来自造山带的其他构造单元.针对该问题，在详细的岩相学分析基础上，利用碳质拉曼光谱（Raman spectroscopy of carbonaceous material，RSCM）温度计对木扎尔特东侧的阿克牙孜河下游地区多个剖面开展了变质温度研究.根据结构构造特征将这些岩石分为具有变余沉积结构构造且发生不同程度糜棱岩化的浅变质碎屑岩-碳酸盐岩系列和具有变质结晶结构的片岩-变粒岩系列.RSCM温度计显示前者经历的峰期温度为465~597℃，原岩很可能为卷入造山带的石炭纪地层，抬升过程中局部发生糜棱岩化.后者峰期温度为552~617℃，绿片岩相叠加期间发生C-O-H流体活动，可能属于伊犁-中天山的变质基底那拉提岩群.研究表明，伊犁-中天山南缘的阿克牙孜下游一带的变质岩具有不同的变质演化历史，它们来自不同的构造单元，并不是木扎尔特高温变质带的延续. 

Complex Evolution of Metamorphic Rocks from Lower Part of Akeyazi Valley,SW Tianshan: Implications from Thermometry Based on Raman Spectroscopy of Carbonaceous Material

As a result of the collision between the Tarim plate and the Yili-Central Tianshan plate, the orogenic belt of Southwest Tianshan has experienced secular complex evolution. Metamorphic studies at the southern margin of the Yili-Central Tianshan plate are significant in deciphering the geological history of this orogenic belt. Although metamorphic rocks are widely distributed in this region, study focuses are mainly on the Muzhaerte high-grade rocks. The spatial distribution and tectono-metamorphic evolution of other metamorphic rock types from the same tectonic belt are poorly known. Whether they occur as part of a coherent high-temperature terrane or any other tectonic nappes is fundamental to reconstruct the orogeny of Southwest Tianshan. To resolve this issue, we carry out detailed petrography and temperature estimates using the RSCM (Raman spectroscopy of carbonaceous material, RSCM) thermometry for metamorphic rocks from several sections of the lower part of the Akeyazi valley. Based on textural and structural observations, two types of metamorphic rocks are grouped. Type 1 rocks consist of meta-sedimentary rocks (i.e., meta-siliciclastic and meta-carbonate rocks), with rounded detrital minerals (e.g., quartz and feldspar) and bedding structure locally modified by strong shearing. Type 2 rocks include mica schists and quartzofeldsparthic rocks, uniformly consisting of metamorphic minerals with lepidoblastic to granoblastic texture and well-developed schistosity. The RSCM thermometry suggests that peak temperatures of the former group are 465-597 ℃. They were probably derived from the Carboniferous strata and were locally subjected to mylonitization. Peak temperatures of the latter group are 552-617 ℃, probably as part of the pre-Cambrian basement (the Nalati Group) and they were infiltrated by C-O-H fluids during shearing at shallower levels. This study suggests that the metamorphic rocks of the Lower Akeyazi River have contrasting metamorphic histories and come from different tectonic units, not as an eastern extension of the Muzhaerte high-temperature belt.