岩石矿物学杂志2025，Vol.44Issue(5)：1028-1050,23.DOI:10.20086/j.cnki.yskw.2025.4193
东昆仑三叠纪两期长英质火山活动的时代与动力学背景
Ages and tectonic settings of two episodic Triassic felsic volcanism in the East Kunlun:Constraints from zircon U-Pb geochronology and geochemistry
摘要
Abstract
The Triassic volcanic rocks in the East Kunlun Orogenic Belt(EKOB)hold valuable magmatic-tectonic information,serving as a crucial probe to investigate the processes of the Paleo-Tethys orogeny.This study focuses on the Middle Triassic Naocangjiangou Formation and the Late Triassic Elashan Formation volcanic rocks,emphasi-zing petrology,zircon U-Pb geochronology,and zircon trace elements geochemistry to provide key evidence for the magmatic-tectonic evolution of the EKOB during the Triassic.The Naocangjiangou Formation is predominantly com-posed of dacites,while the Elashan Formation primarily consists of rhyolites and andesites.Geochronological results indicate that the dacites of the Naocangjiangou Formation formed during the Middle Triassic(249～243 Ma),whereas the rhyolites and andesites of the Elashan Formation formed in the Late Triassic(221～219 Ma).Zircons from the Middle Triassic dacites can be classified into two types based on Ti content:low-Ti(1.42×10-6 to 4.83× 10-6)and high-Ti(3.25×10-6 to 72.5×10-6).The low-Ti zircons exhibit lower rare earth element(REE)contents(561×10-6 to 1 190×10-6),while the high-Ti zircons have higher REE contents(1 817×10-6 to 6 236×10-6).Late Triassic andesitic magmatic zircons show relatively high Ti contents(11.3×10-6 to 31.2×10-6)and lower REE con-tents(Σ REE=312 ×10-6 to 1 107 × 10-6),whereas Late Triassic rhyolitic zircons exhibit lower Ti contents(1.70×10-6 to 8.58×10-6)and REE contents(355×10-6 to 1 670×10-6).Zircon genesis analysis reveals that the high-Ti zircons in the Middle Triassic dacites are hydrothermal in origin,while the low-Ti zircons from the Middle Triassic and all Triassic zircons from the Late Triassic are of typical magmatic origin.Zircon Ti thermometry and crustal thickness studies indicate a significant increase in magmatic temperatures and crustal thickening in the EKOB between 243 Ma and 219 Ma.Synthesizing regional geological data,this study concludes that the EKOB ex-perienced continuous subduction of the Paleo-Tethyan oceanic crust during the Middle Triassic,followed by crustal thickening due to collision in the Late Triassic.Notably,no significant lithospheric thinning occurred in the EKOB during the Triassic.This research further demonstrates that zircon trace element compositions cannot reliably reveal the tectonic settings of felsic magmatic rocks in orogenic belts,underscoring the need for cautious application of this method.关键词
东昆仑/古特提斯/火山岩/锆石地球化学/大地构造Key words
East Kunlun/Paleo-Tethys/volcanic rocks/zircon geochemistry/tectonic分类
天文与地球科学引用本文复制引用
赵昱杰,熊富浩,闫东东..东昆仑三叠纪两期长英质火山活动的时代与动力学背景[J].岩石矿物学杂志,2025,44(5):1028-1050,23.基金项目
国家自然科学基金项目(41602049) （41602049）
四川省自然科学基金项目(2024NSFSC1991) （2024NSFSC1991）
自然资源部黄河上游战略性矿产资源重点实验室科研项目(YSJD2022-14) （YSJD2022-14）
中国地质调查局项目(DD20240074-02) National Natural Science Foundation of China(41602049) （DD20240074-02）
Natural Science Foundation of Sichuan Province(2024NSFSC1991) （2024NSFSC1991）
Key Laboratory of Strategic Mineral Resources of the Upper Yellow River,Ministry of Natural Resources(YSJD2022-14) （YSJD2022-14）
China Geological Survey(DD20240074-02) （DD20240074-02）
