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西南天山高压-超高压变质带东段特克斯县科克苏河一带首次发现了榴辉岩和含绿辉石的蓝片岩,通过详细的岩石学研究,并运用THERMOCALC软件、在MnNC(K)FMASHO体系下对其进行了相平衡模拟.选择的样品为新鲜的榴辉岩TK003,含绿辉石包体的蓝片岩TK026-8及退变榴辉岩TK027.3个样品石榴石成分均显示出从核部到边部Xpy和Xgrs逐渐升高,Xsps不断降低的变质生长环带特征.相平衡模拟结果显示,榴辉岩和蓝片岩经历了相似的P-T演化轨迹,早期近等压条件下升温至峰期,达到榴辉岩相变质作用温压范围,峰期温压条件为T=480~515℃,P=2.0~2.3 GPa;而后在近等温条件下快速降压,退变初期经历的温压条件为515~519℃,1.78~1.93 GPa.不同样品中变质矿物组合及其含量的不同主要受全岩成分控制的退变路径不同所引起,此外还可能与体系含水量有关.峰期温压条件及其地热梯度(6~7℃km-1)表明科克苏河流域出露的高压变质岩石同样经历了冷俯冲榴辉岩相变质作用,它与西端的昭苏境内的榴辉岩-蓝片岩带相连,构成了东西向长约200 km的榴辉岩相变质带.但在该区并未发现超高压变质矿物,说明西南天山东段的科克苏河一带可能没有俯冲到达发生超高压变质作用的深度.
The eclogite and the omphacite-bearing blue-schist rocks were first discovered in the area of the Coxueshe River in the Turks High-Pressure Metamorphic Belt in the Tethus of Southwest Tianshan. Through detailed petrological studies and the use of THERMOCALC software, ) FMASHO system, the samples were selected as fresh eclogite TK003, blue pluton TK026-8 with omphacite inclusions and TK027.3 degenerate eclogites Showing the gradual increase of Xpy and Xgrs from the nucleus to the margin and Xsps decreasing metamorphic growth zone characteristics.The phase equilibrium simulation results show that the eclogite and blue schist undergo a similar PT evolution trajectory and the early near isobaric conditions The temperature and pressure at the peak temperature were T = 480-515 ℃, P = 2.0-2.3 GPa. After that, the blood was depressurized rapidly in the near isothermal condition and the initial stage of degeneration The temperature and pressure conditions experienced were 515-519 ℃ and 1.78-1.93 GPa. The differences of metamorphic mineral assemblages and their contents in different samples were mainly caused by the different degenerate paths controlled by the whole rock components, and may also be related to the water content of the system. Peak temperature and pressure conditions and the geothermal gradient (6 ~ 7 ℃ km-1) that Cork Su River The high-pressure metamorphic rocks exposed in the domain also experienced cold subduction eclogite facies metamorphism, which is connected with the eclogite-blue schist belt in Zhaosu area at the west end, forming eclogite facies metamorphism with an east-west length of 200 km However, no UHP metamorphic minerals were found in the area, indicating that there may be no subduction reaching the depth of UHP metamorphism in the Coxe Su River in the eastern Tianshan Mountains.