Volume 93, Issue 5 pp. 1261-1280
Original Article
Full Access

Zircon U-Pb Ages and Geochemistry of Permo-Carboniferous Mafic Intrusions in the Xilinhot Area, Inner Mongolia: Constraints on the Northward Subduction of the Paleo-Asian Ocean

Ke WANG

Ke WANG

School of Earth Sciences, State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan, 430074 China

Search for more papers by this author
Yilong LI

Corresponding Author

Yilong LI

School of Earth Sciences, State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan, 430074 China

Corresponding author. E-mail: [email protected]Search for more papers by this author
Wenjiao XIAO

Wenjiao XIAO

State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029 China

Search for more papers by this author
Jianping ZHENG

Jianping ZHENG

School of Earth Sciences, State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan, 430074 China

Search for more papers by this author
Fraukje M. BROUWER

Fraukje M. BROUWER

Geology and Geochemistry Group, Department of Earth Sciences, VU Amsterdam, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands

Search for more papers by this author
First published: 04 October 2019
Citations: 6

About the first author:

WANG Ke, male, born in 1994 in Sanmenxia City, Henan province; a master's degree candidate majoring in igneous petrology and tectonic evolution of orogen at China University of Geosciences (Wuhan). E-mail: [email protected].

About the corresponding author:

LI Yilong, male, born in 1983 in Zaozhuang City, Shandong Province; Ph.D., graduated from Department of Earth Sciences, Vrije Universiteit Amsterdam; associate professor at China University of Geosciences (Wuhan). He is interested in metamorphic petrology and tectonic evolution of orogen. Email: [email protected]

Abstract

The Central Asian Orogenic Belt (CAOB) resulted from accretion during the Paleozoic subduction of the Paleo-Asian Ocean. The Xilinhot area in Inner Mongolia is located in the northern subduction zone of the central-eastern CAOB and outcropped a large number of late Paleozoic mafic intrusions. The characteristics of magma source and tectonic setting of the mafic intrusions and their response to the closure process of the Paleo-Asian Ocean are still controversial. This study presents LA-ICPMS zircon U-Pb ages and geochemical features of mafic intrusions in the Xilinhot area to constrain the northward subduction of the Paleo-Asian Ocean. The mafic intrusions consist of gabbro, hornblende gabbro, and diabase. Their intrusion times can be divided into three stages of 326–321 Ma, 276 Ma and 254 Ma by zircon U-Pb ages. The first two stages of the 326–276 Ma intrusions mostly originated from subduction-modified continental lithospheric mantle sources that underwent a variable degree partial melting (5–30%), recording the subduction of oceanic crust. The third stage of the 254 Ma mafic rocks also show arc-related features. The primary magma compositions calculated by PRIMELT2 modeling on three samples of ∼326 Ma and two samples of ∼254 Ma show that these mafic samples are characterized by a variable range in SiO2 (47.51–51.47 wt%), Al2O3 (11.46–15.55 wt%), ΣFeO (8.27–9.61 wt%), MgO (13.01–15.18 wt%) and CaO (9.13–11.67 wt%), consisting with the features between enriched mantle and lower continental crust. The source mantle melting of mafic intrusions occurred under temperatures of 1302–1351°C and pressures of 0.92–1.30 GPa. The magmatic processes occurred near the crust-mantle boundary at about 33–45 km underground. Combined with previous studies, it is concluded that Carboniferous to early Permian (∼326–275 Ma) northward subduction of the Paleo-Asian oceanic crust led to the formation of the mafic magmatism in the Baolidao arc zone. The whole region had entered the collision environment at ∼254 Ma, but with subduction-related environments locally. The final collision between the North China craton and the South Mongolian microcontinent may have lasted until ca. 230 Ma.

 

    The full text of this article hosted at iucr.org is unavailable due to technical difficulties.