A Combined Paleomagnetic And Zircon U-Pb Geochronological Study On The Zhela Formation Volcanic Rocks In The Tethyan Himalaya

The breakup of Eastern Gondwana and subsequent northward drift of the Indian Plate led to the formation of the eastern Indian Ocean and the closure of the Tethyan Ocean.This geological event has caused long-term impacts on the global paleoclimate and paleogeography,as well as on the evolution of life.Although a large number of geological and geophysical investigations have been performed on the circum-eastern Gondwana magmatic provinces,oceanic lithosphere and surrounding basins,and the Kerguelen mantle plume in the last four decades,the breakup mechanism and process of Eastern Gondwana remain hotly debated.To contribute to solving the issues mentioned above,a combined geochronological and paleomagnetic study was carried out on the Zhela Formation volcanic rocks in the Taga area of the eastern Tethyan Himalaya.Based on new Late Jurassic paleomagnetic and geochronological data,combined with the Late JurassicEarly Cretaceous paleomagnetic and geochronological data obtained from the Tethyan Himalaya,India and Australia,several main conclusions can be drawn as follows:(1)The new zircon U-Pb age reveals that the Zhela Formation volcanic rocks in the Taga area of the Eastern Tethyan Himalaya formed at 147.1±2.5 Ma,which suggests that the sample Zhela Formation volcanic rocks erupted during the Late Jurassic,rather than during the Middle Jurassic as given by 1:250,000 scale Longzi regional geological survey report;(2)A reliable Late Jurassic paleomagnetic pole constrained by positive fold and reversal tests has been obtained from 17 paleomagnetic sites of the Zhela Formation volcanic rocks.This new Late Jurassic pole is located at-30.5°N,324.9°E with dp/dm=11.8°/15.0°,indicating that the Taga sampling area should lie at 44.1°±11.8°S at 147.1±2.5 Ma.(3)Late Jurassic-Early Cretaceous(147.1-124 Ma)igneous rocks in the Eastern Tethyan Himalaya originated from the Kerguelen mantle plume.