Formation of the paleoproterozoic calc-silicate and high-pressure mafic granulite in the Jiaobei Terrane, Eastern Shandong, China

Jiaobei terrane contains low to high grade Paleoproterozoic metamorphosed sedimentary sequence deposited under littoral to neritic environments,belonging to part of the Jiao-Liao-Ji belt of the Eastern Block in the North China Craton.The clock wise P-T paths concluded from HP mafic and pelitic granulites indicate the closing and collisional process of the belt.This study focuses on the formation of calc-silicate that is closely associated with HP mafic granulite.On the basis of mineral assemblage evolution of the PT peudosention in SACFM system,critical metamorphic reactions,combined with calculation of Grt-Cpx thermometer,the precursor granulite is estimated having experienced at least 780~850℃ and 1.0~1.1GPa metamorphic conditions,and retrograde to 400~650℃ and 0.6~0.75GPa.Accordingly,a clock wise P-T path is concluded.Results show that the calc-silicate develops on the late stage of continent-continent collision during the exhumation process of the HP granulite,combined with Ca metasomatism at the same time.Establishment of the genetic relationship of calc-silicate and the mafic garnet granulite present the importance of petrological paragenetic association during the exhumation of collisional metamorphic terrane.