新疆阿尔泰西北部白哈巴一冲乎尔一带加里东和海西两期区域变质作用的厘定
Redefinition of Caledonian and Hercynian regional metamorphism in the Baihaba-Chonghu'er district, northwestern Altay, Xinjiang
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摘要: 提要：通过对新疆西北部阿尔泰白哈巴—冲乎尔一带详细的野外地质填图和综合研究，在原划分的奥陶纪、震旦—寒武纪地层中分别采获了早泥盆世双壳化石，获得了加里东期、海西期不同期次的同位素地质年龄，在浅变质岩中划分出了石英岩状结构亚带和刺状结构亚带，在区域动力热流变质岩中划分出蓝晶石带、矽线石带、铁铝榴石带、十字石带等。新的证据表明，研究区白哈巴地区发育加里东期和海西期两期区域低温动力变质，南东部发育两期区域动力热流变质，海流滩为加里东期，冲乎尔则为海西期，沿库根断裂带产生叠加。这一划分使争论了近半个世纪的该区变质类型和变质世代的问题有了新的答案。Abstract: Abstract：Based on geologic mapping and integrated study in the Baihaba-Chonghuer district, northwestern Altay, Xinjiang, Lower Devonian fossils were collected from the strata that were originally assigned to the Ordovician or Sinian-Cambrian, and Caledonian and Hercynian isotopic geologic ages were acquired in some distinct plutons. Subzones with quartzite-like and thorn-like textures were distinguished in low-grade metamorphic rocks and kyanite, sillimanite, almandine and staurolite zones were recognized from regional dynamic heat-flow metamorphic rocks. The new evidence indicates that the Caledonian and Hercynian phases of regional low-temperature dynamic metamorphism occurred in the Baihaba district of the study area and that two phases of regional dynamic heat-flow metamorphism occurred in the southeastern part of the study area: the Caledonian phase in Hailiutan and the Hercynian phase in Chonghuer, which are superposed along the Kugen fault. This division gives a new answer to the dispute about the metamorphic types and generations in the area that lasted for nearly half century.
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