论文部分内容阅读
在柴达木盆地北缘鱼卡河边达肯大坂杂岩之花岗质片麻岩中发现典型的含柯石英榴辉岩。榴辉岩主要由石榴石、绿辉石和少量（多硅）白云母、柯石英和石英、角闪石、金红石等矿物组成。石榴石中铁铝、镁铝和钙铝榴石分子含量分别为５１％～５９％、２６％～３１％和１３％～１９％；绿辉石中硬玉分子含量为４５％～４８％；岩石中残留有ｂ０值极大的高压矿物多硅白云母（ｂ０＝９０７５×１０－１ｎｍ）；角闪石亦为高压类型的冻蓝闪石；最为重要的是确定了柯石英的存在。榴辉岩原始特征保存完好，仅遭受轻微的退变质作用和叠加变质作用。组成矿物可分为３个世代：（１）峰期矿物组合：石榴石＋绿辉石＋（多硅）白云母＋（柯）石英＋金红石；（２）退变交生组合：冻蓝闪石＋蠕虫状石英；（３）后期叠加变质矿物白云母。榴辉岩相变质作用发生在压力大于２８ＧＰａ的超高压至大约７３０℃、１７０ＧＰａ的高压环境，表明柴达木盆地北缘是一条重要的古板块汇聚边界。
Typical coesite-bearing eclogite is found in the granitic gneisses of the Dakenan Osaka complex on the fiscally bank of the Tagar River in the northern Qaidam Basin. The eclogites are mainly composed of garnets, omphacites and a few (polysilicic) muscovite, coesite and quartz, hornblende, rutile and other minerals. The contents of Fe, Al, Ga and Garnet in the garnet are 51% -59%, 26% -31% and 13% -19%, respectively; the content of jadeite in the omphacite is 45% -48% There remains a high-pressure mineral mica (b0 = 9075 × 10-1nm) with high b0 value; amphibole is also a high-pressure type glaucophane; the most important one is the existence of coesite. The original features of the eclogites are well preserved and suffer only minor retrogressive metamorphism and superimposed metamorphism. Composition of minerals can be divided into three generations: (1) Peak mineral assemblages: garnet + omphacite + (polysilicic) muscovite + (Co) quartz + rutile; (2) Stone + worm-like quartz; (3) late superimposed metamorphic mineral muscovite. The eclogitic facies metamorphism occurs at a UHP pressure of more than 28GPa to a high pressure of about 730 ℃ and 170GPa, indicating that the northern margin of the Qaidam Basin is an important convergence boundary of the old plate.