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长英质浅色体广泛出露于柴北缘造山带中段锡铁山地体花岗质片麻岩中,多呈脉状、不规则透镜状顺区域片麻理走向产出,主要由钾长石、斜长石、角闪石、石英以及少量黑云母组成,是黑云母花岗质片麻岩深融作用的产物。温压估算获得其形成条件为P=(6.5~9.6)′102 MPa,T=640~690℃,达麻粒岩相。选取浅色体角闪石和钾长石单矿物进行激光阶段加热~(40)Ar/~(39)Ar定年。角闪石共进行了17个阶段,其中3~17阶段数据形成平坦年龄谱,坪年龄为442.5±4.0 Ma;构成年龄坪的数据对应的等时线年龄为441.6±3.9 Ma,相应初始捕获氩比值为303±4,暗示该角闪石样品不含过剩~(40)Ar。坪年龄~442.5 Ma解释为角闪石初始结晶年龄,代表了锡铁山地区黑云母片麻岩发生深融(混合岩化)的时代。共生钾长石阶段加热获得一个低温和一个高温坪,坪年龄分别为307.5±2.9 Ma和323.3±3.0 Ma;等时线图谱暗示该钾长石样品未受过剩~(40)Ar干扰。坪年龄分别代表浅色体冷却到钾长石封闭温度~200℃和~250℃的时间。~(40)Ar/~(39)Ar定年结果显示锡铁山黑云母片麻岩深熔作用后经历了低速抬升(0.1~0.2 km/Ma)和缓慢冷却(3~3.6℃/Ma)的演化历史。
The long British quality light bodies are widely exposed in the Xiantie terrane granitic gneiss in the middle of the northern margin of the Qaidam Basin. They are mostly veins, with irregular lenticular patterns leading to the output of malachite products. They are mainly composed of potash feldspar, Plagioclase, amphibole, quartz and a small amount of biotite, which is the product of the deep melting of biotite granitic gneiss. Temperature and pressure estimation obtained the formation conditions for the P = (6.5 ~ 9.6) ’102 MPa, T = 640 ~ 690 ℃, reached granulite facies. Selected light body hornblende amphiboles and single feldspar feldspar laser phase heating ~ (40) Ar / ~ (39) Ar dating. Amphibole has 17 stages, in which the data of 3 ~ 17 stages form a flat age spectrum with Ping age of 442.5 ± 4.0 Ma; the isochron age corresponding to data of age Ping is 441.6 ± 3.9 Ma, corresponding to the initial capture of argon The ratio was 303 ± 4, suggesting that the amphibole sample does not contain excess (40) Ar. The Ping age ~ 442.5 Ma is interpreted as the initial age of amphibole, representing an era of deep melting (mixed rock formation) of biotite gneiss in the Xieshan area. The symbiotic K-feldspar stage heating obtained a low temperature and a high temperature plateau, with an average age of 307.5 ± 2.9 Ma and 323.3 ± 3.0 Ma, respectively. The isochordal pattern indicated that the K-feldspar sample was not disturbed by excess (40) Ar. The plate ages represent the time when the light-colored body is cooled to the potash feldspar enclosure temperature of ~ 200 ° C and ~ 250 ° C, respectively. The results of ~ (40) Ar / ~ (39) Ar dating show that the lithotitization of the lithic micritic gneisses under low velocity (0.1-0.2 km / Ma) and slow cooling (3- 3.6 ° C / Ma) Evolutionary history.