CAJ | 학술논문

含夕线石十字石榴二云斜长片麻岩是沂水杂岩中首次发现的一种少见的变泥砂质岩石,包裹于沂水生心官庄岩浆杂岩体中,为残留的变质表壳岩透镜体,它经历了两期变质作用的改造.早期高角闪岩相变质与区域麻粒岩相变质有关,峰期矿物共生组合主要为:石榴子石(中心域)+黑云母±白云母+斜长石+石英,M1峰期变质温压条件为:T=660±10℃,P=5.7±0.3kb;晚期角闪岩相变质矿物共生组合为:十字石+石榴子石(边部域)+黑云母±白云母+斜长石±夕线石+石英,以形成大量自形-半自形十字石和具有明显的成分环带的石榴子石为特征,晚期石榴子石的形成由核部→边部经历了一降温降压过程,石榴子石核部:T=650±10℃,P=7.7±0.5Kb,石榴子石边部:T=578±10℃,P=4.7±0.1kb;晚期变质作用早期(石榴子石成核)阶段与埋深导致的部分熔融有关,晚期石榴子石生长阶段与岩浆热事件有关.锆石SHRIMP U-Pb定年结果表明:碎屑锆石不一致线上交点年龄为2695±32Ma,代表变泥砂质岩石源区岩浆岩的结晶年龄,变泥砂质岩石的早期变质变质作用年龄小于此值;晚期变质作用年龄为2537±5Ma.
함석선석십자석류이운사장편마암시기수잡암중수차발현적일충소견적변니사질암석,포과우기수생심관장암장잡암체중,위잔류적변질표각암투경체,타경력료량기변질작용적개조.조기고각섬암상변질여구역마립암상변질유관,봉기광물공생조합주요위:석류자석(중심역)+흑운모±백운모+사장석+석영,M1봉기변질온압조건위:T=660±10℃,P=5.7±0.3kb;만기각섬암상변질광물공생조합위:십자석+석류자석(변부역)+흑운모±백운모+사장석±석선석+석영,이형성대량자형-반자형십자석화구유명현적성분배대적석류자석위특정,만기석류자석적형성유핵부→변부경력료일강온강압과정,석류자석핵부:T=650±10℃,P=7.7±0.5Kb,석류자석변부:T=578±10℃,P=4.7±0.1kb;만기변질작용조기(석류자석성핵)계단여매심도치적부분용융유관,만기석류자석생장계단여암장열사건유관.고석SHRIMP U-Pb정년결과표명:쇄설고석불일치선상교점년령위2695±32Ma,대표변니사질암석원구암장암적결정년령,변니사질암석적조기변질변질작용년령소우차치;만기변질작용년령위2537±5Ma.
A kind of metapelite of sillimanite-bearing staurolite-garnet-two-mica plagiogneiss is recognized at first time, which is as a relic of metamorphic supracrustal rock in the Niuxinguanzhuang magmatic complex. Two metamorphic phases are recognized by assemblage minerals in the rock. The first metamorphic phase (M_1) is of high amphibolite facies, the peak-assemblage minerals include garnet (M_1)+biotite±muscovite+plagioclase+quartz±staurolite, which is related to the regional granulite facies metamorphism. The peak metamorphic conditions estimated by core-component of garnet are about T=660±10℃ and P=5.7±0.5kb respectively. The second metamorphic phases (M_2) is of amphibolite facies which the assemblage minerals include staurolite+garnet (M_2)+biotite±muscovite+plagioclase+sillimanite+quartz. The feature of assemblage minerals show that formed hair-sillimanite and garnet with clear component zones and a lots of subhedral-euhedral staurolite porphyroblasts. The metamorphic conditions that estimated by the components of garnet (M_2) core and rim, are about T=650±10℃ and P=7.7±0.3kb, and T=578±10℃ and P =4.7±0. 1 kb. It shows that garnet (M_2) growing was at the conditions of decreasing temperature and pressure from core to rim, and garnet-core formed was related to partial melting of the upper crust resulted from burial and garnet growing was related to local contact metamorphism dued to the intrusion of magmatic complex. It is explained that the upper intercept age, 2695±32Ma by SHRIMP dating, of the detrital zircons in the metapelite is the crystallization time of magrnatie reck as the source of metapelite, and the earlier metamorphism of the metapelite is obviously later than this time. The later stage of the second metamorphism, growth of the garnet (M_2), took place at 2537±5Ma.