Chronology,Petrogenesis and Links with Extrusion Tectonics of Cangyuan Cenozoic Intermediate to Acid Intrusive Rocks in Baoshan Block,Eastern Tibetan Plateau
In order to investigate the geochronology,petrogenesis and geodynamicsettingof the Cenozoic igneous rocks in Baoshan block,we have concentrated on the petrology,zircon U-Pb chronology and whole-rock geochemical composition of the Early Cenozoic igneous rock in Cangyuan,southeastern Baoshan block. The results of dating indicate that the intermediate to flesic intrusions and dykes in Cangyuan emplaced at 40-41Ma,synchronous with those in Lancang region. The Early Cenozoic igneous rock in Cangyuan and Lancang exhibits high Sr /Y,La /Yb,Gd /Yb ratios and significant REE fractionation,with no significant Sr,Eu negative anomaly,similar to C-type adakite. They have enriched initial ~(86)Sr / ~(87)Sr ratios of 0.7065-0.7103,epsilon_(Nd) (t) values of -3.6 to -5.6. We infer that the Cangyuan Cenozoic magmatism resulted from partial melting of garnet amphibolite in lower crust at a depth of 30 ~ 40km. In addition,we report for the first time that there has ~ 41Ma A-type granite in Cangyuan region in this study. The early Cenozoic igneous rock in both Cangyuan and Lancang have close spatial,temporal and possibly has genetic linkage with the eastward extrusion of Tibet.
