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东海ZK703钻孔位于苏鲁超高压变质带南部,钻孔深558m,穿过的岩性主要为榴辉岩、黑云斜长片麻岩和石榴橄榄岩,及少量多硅白云母石英片岩、石榴石多硅白云母石英片岩、蓝晶石石英岩和硬玉石英岩。钻孔揭示榴辉岩呈层状产出,具中等倾角,稳定延伸到钻孔深度以下。超高压矿物或其后成合晶假象在这些岩石中的保存,以及岩石之间的接触关系表明,这是一个整体经历了超高压变质作用的表壳岩和基性-超基性岩组合。据原生次要矿物,超高压榴辉岩可分成5种类型,其中以富金红石榴辉岩为主,多硅白云母榴辉岩和石英榴辉岩次之,夹少量蓝晶石多硅白云母榴辉岩,含极少量次要矿物的普通榴辉岩与石榴橄榄岩伴生。岩相学研究揭示超高压榴辉岩至少经历了3期变质作用,即峰期超高压榴辉岩相,以柯石英、高硅多硅白云母和金刚石的出现为特征;角闪岩相退变质作用,以角闪石、斜长石和黑云母等后成合晶矿物的形成为特征;绿帘角闪岩相,角闪石+钠长石+绿帘石共生。超高压榴辉岩峰期变质作用的pt条件是700～860C,>2.8～3.0GPa,退变质作用pt轨迹表现为早期的近等温降压过程和晚期的降温、降压过程。显微结构和矿物微区化学成分变化表明,超高压矿物减压退变质形成的后成合晶和后成合晶冠状体矿物是域平衡反应或不平衡反应的产物。合晶矿物的?
The East China Sea ZK703 borehole is located in the southern part of the Sulu UHP metamorphic belt with a drilling depth of 558m. The lithology traversed mainly consists of eclogite, biotite plagioclase gneiss and pomegranate peridotite, and a small amount of siliceous muscovite quartz schist, garnet Siliceous muscovite quartz schist, kyanite quartzite and jadeite quartzite. Drilling revealed that the eclogites were layered with moderate dip and extended steadily below the borehole depth. The preservation of ultrahigh-pressure minerals or their subsequent positron fissures in these rocks and the contact between the rocks suggest that this is a combination of epikarst and mafic-ultrabasic rocks that have undergone UHP metamorphism overall. According to the primary secondary minerals, the UHP eclogites can be divided into five types, of which the eclogitic eclogite is the main type, followed by the pliocene eclogite and the quartz eclogite, with a small amount of kyanite polysilicon The dolomite eclogite, a common eclogite with very minor secondary minerals, is associated with garnet peridotite. The petrography shows that UHP eclogites experienced at least three stages of metamorphism, that is, the UHP eclogite facies characterized by the occurrence of coesite, high-silica-rich muscovite and diamond; the amphibolite Metamorphism, with amphibole, plagioclase and biotite and other after into the formation of crystalline minerals are characterized; green curtain amphibolite facies, hornblende + albite + green curtain symbiosis. The pt condition for the metamorphism of UHP eclogites is 700 ~ 860C,> 2.8 ~ 3.0GPa. The pt trajectory of retrograde metamorphism shows the early near-isothermal depressurization process and the late cooling and depressurization process. The changes of microstructure and chemical composition in the micro-zone indicate that the post-formed and post-formed coronal mineral formed by decompression degeneration of ultra-high pressure mineral is the product of the field equilibrium reaction or the imbalance reaction. Crystal minerals?