宕昌好梯第三纪超镁铁质岩中巨晶及其形成条件

分布于好梯第三纪陆相地层中的超镁铁质岩属碱性超基性岩，为超镁铁煌斑岩。该岩石系中心式超基性火山爆发—喷溢产物。其产出与南北向幔型断裂活动和地幔部分熔融岩浆贯入密切相关。根据岩石组合及产状，好梯陆相超基性火山岩可分为火山颈相、喷发相和次火山岩相。其中火山颈相和喷发相内的碎屑熔岩含有大量的二辉橄榄岩包体，并与单斜辉石和橄榄石巨晶共生。研究结果表明，巨晶系岩浆在上地幔条件下结晶的高压产物

GIANT CRYSTALS OCCURED THE TERTIARY ULTRAMAFIC ROCKS AND THEIR FOMING CONDITIONS IN HAOTI, DANGCHANG COUNTY

The ultramafic rocks in Tertiary Haoti continental facies strata belong to alkline altrabasic rocks named ultramafic lamprophyre. They were fomed by ultrabasic volcanic eruption effusion of central type, which accompanied activity of N-S trend mantle type faults and mantle melted magmatic injection. According to the occurrence and rock assemblage the Haoti continental facies ultrabasic volcanic rocks can be classify into volcanic neck facies, eurption facies and subvolcanic rock facies. There are a lot of lherzolite xenolithes paragerated with olivine and clinopyroxenite giant crystals in the detrital lavas of the volcanic neck facies and eurption facies. Gcological and geochemical data indicate that magma at the upper mantle condition(45km depth) formed the crystal H. P. products-giant crystals.