Affiliation:
1. College of Earth Science, Chengdu University of Technology, Chengdu 610059, China
2. Key Laboratory of Tectonic Controls on Mineralization and Hydrocarbon Accumulation, Chengdu University of Technology, Chengdu 610059, China
3. State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu 610059, China
Abstract
The felsic volcanic rocks in orogenic belts are vital probes to understand the tectonic evolution and continental crust growth. Here, we present a comprehensive study on the zircon U–Pb geochronology, whole-rock geochemistry, and zircon Lu-Hf isotopes of Early felsic volcanic rocks from the Hongshuichuan Formation, East Kunlun Orogen, Northern Tibet, aiming to explore their petrogenesis and implications for the Paleo-Tethyan orogeny and crustal evolution. The studied felsic volcanics comprise rhyolite porphyry and rhyolite, exhibiting coeval zircon U–Pb ages of ca. 247–251 Ma. Rhyolite porphyries show metaluminous to peraluminous nature (A/CNK = 0.88–1.24) with high SiO2 contents (72.1–78.9 wt%) and moderate Mg# values (22–40), and they display enrichment of LREE with (La/Yb)N ratios of 6.02–17.9 and depletion of high field strength elements. In comparison, the rhyolites are strongly peraluminous (A/CNK = 1.09–1.74) with high SiO2 contents (71.7–74.3 wt%) and high Mg# values (43–52) and are also enriched in LREE ((La/Yb)N of 6.65–18.4) and depleted in HFSE (e.g., Nb, Ta, Ti). Combining with their different zircon Lu-Hf isotopes, i.e., enriched isotopes for the rhyolite porphyries (εHf(t) = −7.3 to −3.8) and depleted Hf isotopes for the rhyolites (ɛHf = −0.6 to +3.0), we interpret that the studied rhyolite porphyries and rhyolites were derived by partial melting of Mesoproterozoic metagreywacke sources followed by plagioclase-dominated fractional crystallization, but the latter shows the significant contribution of crust–mantle magma mixing. The mixed mantle-derived magma comes from an enriched lithospheric mantle source that had been metasomatized by subduction-related fluids. Combining with other geological evidence, we propose that the studied Early Triassic felsic volcanic rocks were formed in a subduction arc setting, and the reworking of ancient continental crust with crust–mantle magma mixing is the major mechanism of crustal evolution in the East Kunlun Paleo-Tethyan orogenic belt.
Funder
National Natural Science Foundation of China
Research Project of Chengdu University of Technology
Subject
Geology,Geotechnical Engineering and Engineering Geology
Reference80 articles.
1. Late Paleozoic-Early Mesozoic tectonic-magmatic evolution and mineralization in the eastern section of the East Kunlun Orogenic Belt;Chen;Acta Geol. Sin. (Engl. Ed.),2019
2. Subduction and accretionary tectonics of the East Kunlun orogen, western segment of the Central China Orogenic System;Dong;Earth Sci. Rev.,2018
3. Geological characteristics of Late Paleozoic-Mesozoic unconformities and their response to some significant tectonic events in eastern part of Eastern Kunlun;Li;Earth Sci. Front.,2012
4. Petrogenesis of peralkaline rhyolites in an intra-plate setting: Glass House Mountains, southeast Queensland, Australia;Shao;Lithos,2015
5. The Tarim picrite–basalt–rhyolite suite, a Permian flood basalt from northwest China with contrasting rhyolites produced by fractional crystallization and anatexis;Tian;Contrib. Mineral. Petrol.,2010