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中国大陆科学钻探工程预先导孔CCSD-PP1中存在两类不同性质的花岗质片麻岩,它们的岩相学性质、地球化学特征、锆石中的包体矿物组合和分布规律以及阴极发光图像均存在明显的差别。其中第一类花岗质片麻岩中的锆石呈完好的自形晶,不含任何超高压矿物包体,自晶体中心至边缘均具有典型的岩浆结晶生长环带,表明该类花岗质片麻岩未经历超高压变质作用;第二类花岗质片麻岩中的锆石呈半自形晶—它形晶,晶体核部保存典型的岩浆结晶生长环带,且无超高压矿物包体,具有继承性锆石的特点。而在晶体的过渡带及其与边缘的交界部位,普遍存在以柯石英为代表的包体矿物,表明第二类花岗质片麻岩曾经历了超高压变质作用,且锆石在此变质过程进一步结晶生长,形成新的生长环带。该项成果对于深入探讨苏鲁超高压变质带的俯冲-折返机制及其与岩浆作用的相互关系以及对中国大陆科学钻探工程的选址和实施有着重要的科学意义。
There are two types of granitic gneiss in CCSD-PP1, a Chinese prestablished pilot hole in the Chinese mainland, which have petrography, geochemical characteristics, assemblage and distribution of inclusions in zircon, and cathodoluminescence There are obvious differences between the images. The first type of granitic gneiss in the zircon is intact self-shaped, does not contain any ultra-high pressure mineral inclusions, from the center of the crystal to the edge of the typical magmatic crystal growth zone, indicating that the type of granite The gneisses have not undergone UHP metamorphism. The zircons in the second type of granitic gneiss have a semicircle-shaped crystal, which is typical of the magma crystal growth zone in the nucleus of the crystal, Mineral inclusions, with inherited zircon characteristics. In the transitional zone of the crystal and its boundary with the edge, the enclave minerals represented by coesite are ubiquitous, indicating that the second type of granitic gneiss has experienced the process of UHP metamorphism and the zircon is altered here The process of further crystal growth, the formation of a new growth zone. This result is of great scientific significance for further exploration of the subduction-reentry mechanism and its interaction with magma in the ultra-high-pressure metamorphic belt of the Sulu and the site selection and implementation of the scientific drilling project in mainland China.