SHRIMP zircon U-Pb dating of the intrusives in the Tongling metallogenic cluster and its dynamic setting |
| |
Authors: | GanGuo Wu Da Zhang YongJun Di WenShuan Zang XiangXin Zhang Biao Song ZhongYi Zhang |
| |
Institution: | (1) State Key Laboratory of Geological-Processes and Mineral Resources, China University of Geosciences, Beijing, 100083, China;(2) Shijiazhuang University of Economics, Shijiazhuang, 050031, China;(3) Institute of Geology, Chinese Academy of Geological Sciences, Beijing, 100037, China |
| |
Abstract: | This paper selected five typical Mesozoic intrusives from the Tongling metallogenic cluster (Xiaotongguanshan, Fenghuangshan,
Xinqiao, Dongguashan, and Shatanjiao plutons), and made a systemic SHRIMP zircon U-Pb dating for the five plutons, which produced
an age range of 151.8±2.6–142.8±1.8 Ma. This work put an accurate constraint on the formation age of the intrusives in the
Tongling metallogenic cluster. These age data indicate that magmatic activity reached a peak during Late Jurassic. The intrusive
sequence of magma is generally from quartz monzonite (porphyry) through monzonite to granodiorite to quartz monzodiorite to
pyroxene monzodiorite to gabbro-diabase. The intrusives of different lithology differed in crystallization age, probably implying
the intrusives in the Tongling area underwent an evolutional process of magma, which was closely related to geodynamical setting
in the depths of the area. A dynamic model was presented for the origin of the igneous rocks in the study area as follows.
The assembly between the Yangtze craton and the North China craton finished at the end of T3, and then the stage of another compressional orogeny began in the Tongling area, i. e., Pacific dynamic system. Along with
the subduction of the Izanagi plate underneath the Eurasian plate at J2-J3, NW-trending compression toward the East China continent was produced, and compressional deformation also took place, forming
NE-trending fold and resulting in thickening of the crust in the Tongling area. High-density eclogite-facies rocks were produced
in the low part of the crust, resulting in the delamination of mantle lithosphere and lower crust, and upwelling of materials
in asthenosphere. Decompression melting produced basaltic magma, and the materials in lower crust were heated by the underplating
of the basaltic magma. Thus, melting of lower crust yielded granitic magma, which intruded along deep and large faults through
various geological processes (J3-K1). The SHRIMP U-Pb zircon age of 151.8±2.6–142.8±1.8 Ma for intrusives in the Tongling area suggests that the delamination
of lithosphere mantle and lower crust at least began at middle-late stage of Late Jurassic, resulting in sharp thinning of
lithosphere and intense extension of middle-upper crust. Thus, a lot of decollements were produced between cover and cover,
basement and cover, and middle and lower crust. This was structural layering or detachment of lithosphere in the Tongling
area. Three concordant ages for old inherited cores of magmatic origin (747–823 Ma) indicated that there were obvious magmatism
in the Tongling area during Neoproterozoic, and a little more of the Neoproterozoic igneous source rocks participated in the
formation of Mesozoic intrusives.
Supported by the National Natural Science Foundation of China (Grant No. 40434011), the Major State Basic Research Program
(Grant No. 1999CB043206) and the National Natural Science Foundation of China (Grant No. 40372050) |
| |
Keywords: | intrusive rocks SHRIMP U-Pb dating of zircons geodynamics Neoproterozoic the Tongling metallogenic cluster area |
本文献已被 SpringerLink 等数据库收录! |
|