Report
Making continental crust: origin of Devonian orthogneisses from SE Mongolian Altai
| العنوان: | Making continental crust: origin of Devonian orthogneisses from SE Mongolian Altai |
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| المؤلفون: | Hanzl, Pavel, Schulmann, Karel, Janousek, Vojtech, Lexa, Ondrej, Hrdlickova, Kristyna, Jiang, Yingde, Burianek, David, Altanbaatar, Battushig, Ganchuluun, Turbat, Erban, Vojtech |
| بيانات النشر: | CESKA GEOLOGICKA SPOLECNOST |
| سنة النشر: | 2016 |
| المجموعة: | Guangzhou Institute of Geochemistry: GIG OpenIR (Chinese Academy of Sciences) / 中国科学院广州地球化学研究所机构知识库 |
| مصطلحات موضوعية: | Geochemistry & Geophysics, Mineralogy, Devonian orthogneiss, whole-rock geochemistry, U-Pb geochronology, crustal architecture, continental crust growth, Mongolian Altai, ASIAN OROGENIC BELT, HF ISOTOPIC COMPOSITIONS, ZIRCON U-PB, SW MONGOLIA, WESTERN MONGOLIA, CHINESE ALTAI, TSEEL TERRANE, ICP-MS, EXTRACTION CHROMATOGRAPHY, PERALUMINOUS GRANITES |
| الوصف: | Orthogneiss and meta-rhyolite bodies from different crustal levels of the Tseel Terrane in the Mongolian Altai were examined using multidisciplinary approach involving structural geology, whole-rock geochemistry and U-Pb zircon geochronology. The orthogneisses form sheet-like bodies parallel with dominant sub-horizontal metamorphic fabric which was heterogeneously verticalized along localized zones of deformation at boundaries of lower and middle crustal domains. Three samples of orthogneisses yielded Late Devonian LA-ICP-MS U-Pb zircon ages of 373 +/- 3, 377 +/- 5 and 379 +/- 2 Ma (2 sigma), which are interpreted as crystallization ages of felsic magmas. The meta-rhyolite displays poorly constrained, older U-Pb zircon ages of 380 +/- 4 and 403 +/- 5 Ma, which are also considered as intrusive. Whole-rock geochemistry, including relatively little fractionated REE patterns, as well as radiogenic whole-rock Nd and zircon Hf isotopic signatures point to a rather primitive source of the granitic protoliths. The high-K calc-alkaline chemistry and LILE over HFSE enrichments in the NMORB-normalized spider plots indicate an arc-related origin. Juvenile character of the studied rocks was confirmed by Nd and Hf crustal residence ages that are mostly 0.8-0.9 Ga. The origin of the metaigneous rocks is interpreted in terms of partial melting of Neoproterozoic to Cambrian magmatic arc-derived material, probably dominated by immature psammitic sediments (graywackes). This study brings important arguments that the orthogneisses do not represent an old crystalline basement previously assumed in the Mongolian Altai. A model is proposed suggesting formation of mature and layered continental crust by syn-orogenic melting of youthful volcanosedimentary wedge and emplacement of sub-horizontal syn-orogenic magmatic sheets at all crustal levels during crustal-scale vertical shortening. The vertical shortening was probably connected to lithospheric-scale extensional event associated with massive heat influx and emplacement of juvenile ... |
| نوع الوثيقة: | report |
| اللغة: | English |
| Relation: | JOURNAL OF GEOSCIENCES; http://ir.gig.ac.cn/handle/344008/55196 |
| DOI: | 10.3190/jgeosci.206 |
| الاتاحة: | http://ir.gig.ac.cn/handle/344008/55196 https://doi.org/10.3190/jgeosci.206 |
| رقم الانضمام: | edsbas.D8A514B6 |
| قاعدة البيانات: | BASE |
| DOI: | 10.3190/jgeosci.206 |
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