苏鲁–大别高压变质带东北向延伸及地质演化探讨Investigation of Northeast Extension and Geological Evolution of the Sulu-Dabie High-Pressure Metamorphic Belt
尹启航, 马鹏飞, 李旭平
千里岩岛, 榴辉岩, 温压条件, P-T轨迹, 地质年代Qianliyan Island, Eclogite, P-T Condition, P-T Path, Metamorphic Age
《Advances in Geosciences》, Vol.6 No.3, 2016-06-28
位于中国黄海北部青岛以东约80 km的千里岩岛发育有透镜状和层状榴辉岩。通过千里岩岛与中国苏鲁大别造山带两地榴辉岩在矿物特征、形成年代、变质峰值温压条件等地质环境方面的对比，表明千里岩岛是苏鲁大别造山带海上的延伸。根据岩相学和矿物学研究千里岩岛榴辉岩主要经历了三个变质阶段：以榴辉岩中Grt-Omp-Ph-Rt矿物组合为标志的第一变质阶段，T = 775℃，P = 2.6 GPa；以取代绿辉石的Amp + Ab后成合晶结构为标志的第二变质阶段，T = 740℃~790℃，P = 1.60~1.75 GPa；以出现阳起石，进入绿片岩相阶段为标志的第三变质阶段。千里岩岛榴辉岩的变质年代约为222 Ma的晚三叠世，与苏鲁–大别造山带榴辉岩变质年代一致。推测千里岩岛是苏鲁大别造山带东向海上的延伸，并且是韩国洪城与中国苏鲁大别造山带之间的连接部分。
The Qianliyan Island locates at the northern Yellow Ocean about 80 km east from Qingdao, which develops lenses and layers of eclogite. The Qianliyan Island has been considered as the marine extension of the Dabie-Sulu orogen by comparing these two geological settings, especially their eclogites characteristics, such as mineral assemblages and compositions, temperature and pressure conditions, P-T path and geochronology. Based on textures and mineral compositions, three metamorphic stages were distinguished. The first stage is symbolized by the peak metamorphic assemblage of Grt-Omp-Ph-Rt in ecologite, T = 775˚C, P = 2.6 GPa. The second stage is represented by the retrograde assemblage amphibole + albite which form the symplectites around omphacite in eclogite, T = 740˚C~790˚C, P = 1.60~1.75 GPa. The third stage is symbolized by the actinolite ap-pearing as a symbol of greenschist facies. The metamorphic age of the Qianliyan eclogite is docu-mented at the age of the late Triassic ~222 Ma, consistent with those from Dabie-Sulu eclogites. It is proposed that the Qianliyan Island not only is the marine extension of the Dabie-Sulu orogen, but also may be the connecting part between Hongsong, South Korea, and the Dabie-Sulu orogen of China.