Petrogenesis and tectonic implications of Early Cretaceous high-K calc-alkaline volcanic rocks in the Laiyang Basin of the Sulu Belt, eastern China

摘要: Early Cretaceous high-K calc-alkaline volcanism occurring in the Laiyang Basin north of Sulu high-pressure to ultrahigh-pressure (HP-UHP) Metamorphic Belt, eastern China, comprises a wide spectrum rock types, ranging from trachybasalts trachydacites. The basaltic-andesitic rocks erupted at 107-105 Ma, spanning an SiO2 range 50.1-59.6% and MgO 2.6-7.2%, are characterized by large ion lithophile element (LILE; e.g. Ba K) light rare earth (LREE) enrichment, high field strength (HFSE) depletion highly radiogenic Sr but non-radiogenic Nd isotopic compositions (Sr-87/Sr-86(i) = 0.70750-0.70931; epsilon(Nd)(t) -17.9 - -15.6). geochemical similarities between these earlier Belt lamprophyres suggest that both types mafic were derived similar mantle sources with LILE LREE enrichment. Thus, Wulian-Qingdao-Yantai Fault separates two terranes surface should not be considered as lithospheric boundary North China Yangtze blocks. felsic lavas 93-91 61.6-67.0% 1.1-2.6%, show trace geochemistry basaltic rocks, higher even lower 0.70957-0.71109; -19.1 -17.5), I-type granitoids Belt. A crustal origin was proposed explain their (which comparable those experimental slab melts), > 10 Ma eruption interval compositional gaps some elements (e.g. P, Ti Sr) them older rocks. These melts predominant metaigneous protoliths containing accumulative counterparts and/or lamprophyric magmas. extensive extrusion favored extensional regime response progressive attenuation thickened lithosphere orogenic collapse, reflected development basin foreland (before end Jurassic period) fault (since period).