CAJ | 학술논문

早古生代西伯利亚克拉通南缘发生了大规模的增生-碰撞造山运动,本文研究的地区--奥里洪地块记录了巴尔古津微板块与西伯利亚克拉通碰撞造山的事件.对奥里洪地块出露的两种典型的高级变质岩--石榴辉石岩和石榴黑云片麻岩的矿物成分分析和变质温压计算,表明它们都经历了麻粒岩相的峰期变质作用,峰期变质温度达到770～800℃,而压力曾达到1.0GPa左右:峰后的退变质作用仍具有较高的温度,但压力明显降低(700～730℃,0.065GPa和710～766℃,0.50GPa),显示了一个近等温降压(ITD)的顺时针P-T轨迹特征.石榴黑云片麻岩中变质锆石的原位LA-ICP-MS U-Pb定年表明,麻粒岩相峰期变质年龄为479±2Ma,而峰前变质可能在500Ma就已经开始.峰后的退变质作用很可能发生在475～460Ma之后.整个造山作用持续了至少35Ma.对比蒙古-图瓦地块及中国东北佳木斯-额尔古纳地块已厘定出的变质作用及岩浆活动年龄可以发现,西伯利亚克拉通南缘不同地区增生-碰撞造山作用发生的时间是不同的,奥里洪地区造山作用相对年轻.
조고생대서백리아극랍통남연발생료대규모적증생-팽당조산운동,본문연구적지구--오리홍지괴기록료파이고진미판괴여서백리아극랍통팽당조산적사건.대오리홍지괴출로적량충전형적고급변질암--석류휘석암화석류흑운편마암적광물성분분석화변질온압계산,표명타문도경력료마립암상적봉기변질작용,봉기변질온도체도770～800℃,이압력증체도1.0GPa좌우:봉후적퇴변질작용잉구유교고적온도,단압력명현강저(700～730℃,0.065GPa화710～766℃,0.50GPa),현시료일개근등온강압(ITD)적순시침P-T궤적특정.석류흑운편마암중변질고석적원위LA-ICP-MS U-Pb정년표명,마립암상봉기변질년령위479±2Ma,이봉전변질가능재500Ma취이경개시.봉후적퇴변질작용흔가능발생재475～460Ma지후.정개조산작용지속료지소35Ma.대비몽고-도와지괴급중국동북가목사-액이고납지괴이전정출적변질작용급암장활동년령가이발현,서백리아극랍통남연불동지구증생-팽당조산작용발생적시간시불동적,오리홍지구조산작용상대년경.
A series of accretion-collision events occurred along the southern margin of the Siberian Craton in Early Paleozoic. The Olkhon terrane records the history of the accretion and collision between the Barguzin microcontinent and southern Siberian Craton. Mineral composition analyses and P-T calculations of two typical high-grade metamorphic rocks, the garnet pyroxenite and garnet-biotite gneiss in the Olkhon area indicate that both of them experienced granulite facies metamorphism with peak conditions of 770 ～ 800℃, ～ 1.0GPa. The retrograde metamorphism also experienced relatively high temperature, but significantly deceased pressure (700 ～ 730℃, 0.65GPa and 710 ～766℃, 0.50GPa), showing approximately an isothermal decompression clockwise P-T-t path. In-situ LA-ICPMS U-Pb dating results of metamorphic zircons from the garnet-biotite gneiss indicate that peak metamorphism probably took place at 479±2Ma, and pre-peak metamorphism may occurred before 500Ma. The post-peak retrograde metamorphism possibly happened after 475 ～460Ma associated with post-orogenic magmatism. Therefore, the accretion-collision events might have lasted for at least 35Ma. Based on the difference in the time of metamorphism and magmatic activities among Mongolian-Tuva terrane, Jiamusi-Erguna terrane and Olkhon terrane, it is suggested that the accretion-collision events along the southern margin of the Siberian Craton occurred in different periods, and the collision orogeny between the Barguzin microcontinent and the Siberian Craton is slightly later than other terranes.