The Early Permian Tarim Large Igneous Province in Northwest China

Tectonics, Petrology, Geochemistry, and Geophysics

Shufeng Yang, Hanlin Chen

• Publisher: Elsevier
• Year: 2018
• ISBN:
  9780128129388
• Topic: Physical Sciences
• Subtopic: Geology & Earth Sciences

The Early Permian Tarim Large Igneous Province in Northwest China: Tectonics, Petrology, Geochemistry, and Geophysics is the first book to introduce the Early Permian Tarim Large Igneous Province. Based on more than twenty years of study, this book systematically presents time-spatial, geochemical and geodynamic features, along with the metallogenesis and magma evolution of the Early Permian Tarim Large Igneous Province. Furthermore, it provides a new geodynamic model for Large Igneous Provinces. It is intended for researchers and graduate students in tectonics, igneous petrology, geochemistry, geophysics, earth evolution and planetary geology in addition to mining industry professionals.

• Provides the temporal-spatial features of the Early Permian Tarim Large Igneous Province using seismic and borehole data
• Presents petrological and geochemical features and magma evolution of the rock units in Early Permian Tarim Large Igneous Province
• Builds up a new model for Large Igneous Provinces based on the information from the Early Permian Tarim Large Igneous Province

1

Introduction

Abstract

This chapter includes the tectonic evolution of the Tarim Block, a brief introduction to Large Igneous Provinces (LIPs) and a history of the research on the Early Permian Tarim Large Igneous Province (Tarim LIP). The first part introduces the evolution of the basement during the tectonic episodes at 2.65–2.45 Ga, 2.0–1.8 Ga and 1.1–0.9 Ga, and the evolution of sedimentary cover sequences since the Late Neoproterozoic and igneous activity. The second part introduces the concept of LIPs, their classification, the age spectrum of selected LIP events through time and the effect of LIPs on the evolution of the Earth, environmental change ore deposits, etc. The third part introduces a history of research on Tarim LIP and its basic characteristics.

Keywords

Tectonic evolution; History of research; Early Permian Tarim Large Igneous Province (Tarim LIP); Tarim Block

1.1 Tectonic Evolution of the Tarim Block

The Tarim Block and the North and South China Blocks make up the three major continental blocks in China. The Tarim Block occurs within the Xinjiang Uygur Autonomous Region of northwestern China and covers an area of more than 6 × 10⁵ km². It is surrounded by the Tianshan orogen to the north, the Kunlun orogen to the south, and the Altyn-Tagh orogen to the southeast (Fig. 1.1). The main part of the Tarim Block is the Tarim Basin. The Tarim Basin can be divided into several tectonic units including the Kuqa Depression, the North Uplift, the North Depression, the Central Uplift, the Southwest Depression, the Southeast Uplift and the Southeast Depression (Figs. 1.1 and 1.2). A series of important tectonic movements occurred within superimposed basins during different periods. The features and textures of prototype basins were generally superimposed and reconstructed by tectonic movements in later periods due to the unstable tectonics of the Tarim Block which resulted from the relatively smaller scale of the Tarim Craton Block and multiple, intense episodes of tectonic movements in peripheral areas (Jia and Wei, 2002; Jia et al., 2004).

Fig. 1.1 Schematic tectonic map of the Tarim Basin, showing the distribution of tectonic units within the basin (After Liu et al., 2012)

Fig. 1.2 The North to South profile of the Tarim Basin

The Tarim Block is a cratonic block with Archean and Paleo- to Meso-Proterozoic crystalline basements. Sedimentary cover is composed of Neo-Proterozoic, Paleozoic, Mesozoic and Cenozoic.

Most of the Tarim Block is occupied by desert, but outcrops of Precambrian and Paleozoic to Cenozoic rocks are scattered along its margins. The Tarim Block is characterized by a double-layer structure consisting of a metamorphic basement overlain by the Late Neoproterozoic to Cenozoic sedimentary cover sequences.

1.1.1 Evolution of the Basement

The Tarim Block has experienced several stages of tectonic evolution since its formation, and the previous geochronological data from the TTG (Trondhjemite-Tonalite-Granodiorite) and other rocks from the Quruqtagh, Altyn-Tagh and Tiekelike areas suggest that the Tarim Block was mainly built up in several tectonic episodes at 2.65–2.45 Ga, 2.0–1.8 Ga and 1.1–0.9 Ga (Hu et al., 2000; Lu and Yuan, 2003; Zhu et al., 2008; Lu et al., 2008).

The metamorphic basement of the Tarim Block is mainly composed of Archean to Early Neoproterozoic metamorphosed strata and magmatic rocks and it mainly crops out in four areas surrounding the orogenic belts of the basin, i.e. the Korla–Quruqtagh area, the Aksu–Keping area, the Tiekelike area and the Altun–Dunhuang areas at the NE, NW, SW and SE margins of the Tarim Block, respectively (Fig. 1.3). The basement consists of Neoarchean TTG gneisses with minor supracrustals, Paleoproterozoic mafic-felsic intrusions, high-grade supracrustals and minor anatectic granites, and Late Mesoproterozoic to Early–Middle Neoproterozoic meta-sedimentary and volcanic strata metamorphosed in greenschist and blueschist facies, which are together unconformably overlain by Late Neoproterozoic Sinian unmetamorphosed cover. This formation and evolution were closely related to the assembly and breakup of the supercontinents of Columbia (Nuna) and Rodinia (Lu et al., 2008; Zhang et al., 2012).

Fig. 1.3 Geological map showing the spatial distribution of Precambrian rocks in the Tarim Block (Revised from Zhao and Cawood, 2012; Xu et al., 2014)

Neoarchean to Paleoproterozoic rocks in the Tarim Block mostly outcrop along its eastern and northern margins which are mainly exposed in the Quruqtagh and Dunhuang complexes, and include the Neoarchean tonalitic granitic rocks and the Paleoproterozoic amphibolite to granulite facies paragneiss, most of which were emplaced in the period 2.60–2.50 Ga (Lu, 1992; Long et al., 2010, 2011; Shu et al., 2011; Zhao and Gawood, 2012; Zhang et al., 2012). In most places, the Archean rocks outcrop as stripes or lenses with variable dimensions that are tectonically enclosed within the Paleoproterozoic paragneiss; both of them generally show foliations that are concurrent to each other (Zhang et al., 2012). These features suggest that the Archean and Paleoproterozoic rocks had undergone the same tectono-metamorphic event in the Paleoproterozoic Era because the low-grade metamorphic Mesoproterozoic unconformably overlies on the Archean and the Paleoproterozoic rocks (Xijiang BGMR, 1993). In the Qulukatage Complex, these Neoarchean and Paleoproterozoic rocks underwent two metamorphic events at 1.9–1.8 Ga and 1.1–1.0 Ga, which are considered as having been related to the assembly of the Columbia and Rodinia supercontinents, respectively (Shu et al., 2011; Zhang et al., 2012).

Late Mesoproterozoic to Early–Middle Neoproterozoic metamorphosed strata are exposed on the peripheral margins of the Tarim Block, represented by the Bowamu, Aierjigan and Aksu groups on the northern margin, the Kalakashi (Sailajiajitage) and Ailiankate groups on the southern margin, the Bulunkule Group on the southwestern margin, and the Altyn-Tagh Group on the southeastern margin. Most of these groups are considered to have formed in Andean-type continental margins, which were deformed and metamorphosed at 1.0–0.9 Ga, probably related to the assembly of Rodinia (Zhang et al., 2003; Lu et al., 2008).

1.1.2 Evolution of Sedimentary Cover Sequences

Since the late Middle Neoproterozoic, the Tarim Block has become a stable platform overlain by late Middle Neoproterozoic to Cambrian unmetamorphosed cover sequences (Fig. 1.4). The late Middle to Late Neoproterozoic sequences are called the Nahua and Sinian System containing four sequences of tillite, interpreted as evidence for the Neoproterozoic Snow Ball Earth Event. During the Nahua to Sinian, the Tarim Block began to breakup during separation from the Rodinia supercontinent. Rifting-related mafic igneous rocks are widely distributed both in the northern and southern margins of the Tarim Block. The Nahua and Sinian sequences were deposited on the Pre-Nahua crystallized basement unconformably and are composed of glacial deposit conglomerate and terrigenous clastic deposits. The Sinian, overlying unconformably on the Nahua, consists mostly of dolomite and mudstone intercalated with basalt. The thickest deposits of the Sinian in the basin are found in the Manjiaer depression, which was controlled by a group of faults and filled with about 1000 m of deep marine mudstone and muddy limestone with rift volcanic rocks.

Fig. 1.4 Generalized Phanerozoic tectonostratigraphy of the Tarim Block, showing the unconformity-bounded sequences and the evolution of the deposition and the dynamic setting (After Lin et al., 2012)

The Paleozoic series in Tarim exhibit typical features of the sedimentation formed at passive continental margins (Fig. 1.4). Along the southern–southeastern side and the northern side, the thickness of the Paleozoic reaches up to 12 km, and in central Tarim the thickness varies from 5000 m to 8000 m according to data from the boreholes (Jia et al., 2004). The thickness of the Paleozoic sequences in Tarim was strictly constrained by the sedimentary troughs b...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• A series by Zhejiang University Press Advances in China’s Basic Research Editorial Board
• Preface to the Series
• Preface
• 1: Introduction
• 2: Tempo-Spatial Features of the Tarim LIP
• 3: Geochemical Features of the Tarim LIP Rocks and Implications for the Magma Evolution
• 4: Geodynamics of the Tarim LIP
• 5: Metallogenesis of the Tarim LIP
• Index