简介:IntheDiegodeAlmagroarchipelagoofsouthernChile,aquartzrichmicaschistandamylonitizedgranitecontainLateJurassiczirconsofca166and170Marespectively.TheserocksweremetamorphosedduringtheCretaceousinasubductionzoneenvironment,whichdevelopedblueschistassemblagesinmetabasaltsinterleavedwiththemicaschist.ThedatedrockswereprobablypartoftheacidlargeigneousprovincedevelopedinsouthwesternGondwanalandduringtheextensionalphasewhichprecededthedismemberingofthesupercontinent.Theyconstituteevidencethattectonicerosionofthemarginoccurred,asthesesiliceousigneousrocks,formedintheSouthAmericanupperplate,weretransportedinthesubductionzonetosome20kmdepthpriortotheirexhumation.TheserocksareintectoniccontactthroughtheSenoArcabuzshearzone,withlatePermianturbiditesoftheDuquedeYorkcomplex,whichdidnotundergoblueschistmetamorphism.