Affiliation:
1. School of Earth Science and Resources, Chang’an University, Xi’an 710054, China
2. Key Laboratory of Western China’s Mineral Resources and Geological Engineering, Chang’an University, Xi’an 710054, China
Abstract
Late Paleozoic–early Mesozoic intrusive rocks are distributed widely along the northern margin of the Qaidam Basin in the northern Tibetan Plateau. To constrain the tectonic evolution, we carried out petrological, chronological, and geochemical studies of the Chahannuo gabbros. LA-ICP-MS Zircon U–Pb dating yields an age of 255.0 ± 0.9 Ma for the gabbros, which confirms the existence of Indosinian tectono-magmatic activity on the northern margin of the Qaidam Basin. The Chahannuo gabbros have low whole-rock SiO2, Fe2O3 contents, and high Al2O3 contents, which suggests a calc-alkaline affinity. In addition, the gabbros have high MgO, Cr, and Ni contents and Mg#, similar to those predicted of the regional basaltic melts, and indicating that they were affected mainly by fluid from the subducted slab. The Chahannuo gabbros are characterized by arc-like trace element patterns, with enrichment in LREE and LILE, and depletion in HREE and HFSE. No obvious negative Eu anomalies also indicate that no significant magmatic differentiation has occurred. The low Nb/La ratio and Ti content in gabbros samples suggests that the Chahannuo gabbros were partially contaminated by the crust during their formation. The Chahannuo gabbros have high incompatible element ratios (Rb/Sr, Th/Nd, and Th/La), which are closer to the category of enriched mantle. Combing our data with previous data from contemporaneous magmatism in the region, we suggest that the Chahannuo gabbros formed in a continental arc environment related to the northward subduction of the Paleo-Tethyan oceanic plate.
Funder
National Nature Sciences Foundation of China
Natural Science Basic Research Plan in Shaanxi Province of China
Fundamental Research Funds for the Central Universities
Commonweal Geological Survey, the Aluminum Corporation of China and the Land-Research Department of Qinghai Province
Youth Innovation Team of Shaanxi Universities
Subject
Geology,Geotechnical Engineering and Engineering Geology
Reference89 articles.
1. Preliminary division of tectonic units of the Qinghai-Tibet Plateau and its adjacent regions;Pan;Geol. Bull. China,2002
2. The Qinghai-Tibet plateau and continental dynamics: A review on terrain tectonics, collisional orogenesis, and processes and mechanisms for the rise of plateau;Xu;Geol. China,2006
3. Characteristics of the eastern Kunlun orogenic belt;Yin;Earth Sci.,1997
4. Two contrasting eclogite cooling histories, North Qaidam HP/UHP terrane, western China: Petrological and isotope constraints;Zhang;Lithos,2005
5. Geological characteristics and tectonic setting of the Dakendaha Group in Iqe area, northern margin of Qaidam Basin;Wang;Geol. Surv. Res.,2006
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