Provenance and tectonic setting of the Upper Palaeozoic sandstones in western Inner Mongolia (the Shalazhashan and Solonker belts), China: insights from detrital zircon U–Pb ages and Hf isotopes

Provenance and tectonic setting of the Upper Palaeozoic sandstones in western Inner Mongolia (the Shalazhashan and Solonker belts), China: insights from detrital zircon U–Pb ages and Hf isotopes
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DOI：
10.1017/s0016756817000978
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发表时间：
2017
期刊：
Geological Magazine
影响因子：
--
通讯作者：
Li ben
Li ben
中科院分区：
--
文献类型：
--
作者：
Shi Guanzhong;Song Guangzeng;Wang Hua;Huang Chuanyan;Li ben

文献摘要

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The Solonker and Shalazhashan belts are hotly debated tectonic units of the Central Asian.Orogenic Belt (CAOB), because they may either represent a Permian or Triassic suture zone of the.CAOB, or a rifting zone overprinted on an Early Palaeozoic orogen. Provenance analysis of the Upper.Palaeozoic sandstones in these belts may provide useful constraints on this issue. This study collected.six sandstone samples from three study areas: the Mandula area of the Solonker Belt, the Quagan Qulu.area of the Shalazhashan Belt but close to the Alxa block, and the Enger Us area of the Shalazhashan.Belt, for framework petrography, zircon morphology, U–Pb and Lu–Hf isotopic analyses. Framework.petrography reveals that the Mandula and Enger Us area samples contain high proportions of volcanic.fragments, whereas the samples from the Quagan Qulu area include not only volcanic fragments but.also significant amounts of biotite and muscovite. The detrital zircons of the Mandula area and the Enger.Us area yield two main age groups: (i) 260 ̶330 Ma, with dominant εHf(t) values of –5 to +12; and.(ii) 420 ̶550 Ma, with dominant εHf(t) values of –9 to +9, suggesting that Early Palaeozoic arc-related.magmatic rocks and Late Palaeozoic syn-depositional volcanic rocks are the main source rocks. The.detrital zircons of the Quagan Qulu area have one main age group of 420 ̶500 Ma and some grains of.0.9 ̶1.1 Ga, 1.4 ̶1.5 Ga, 1.8 ̶1.9 Ga and ∼ 2.5 Ga, which derive from the northern margin of the Alxa.block. The lithological and fossil assemblages of the Upper Palaeozoic sandstones suggest shallowmarine.to deep-water depositional environments and a northward-deepening transition. Based on the.zircon spectra, sedimentary environment analysis and previous studies, we argue that the Solonker.Belt and the Shalazhashan Belt of the CAOB are in extensional basins of a fore-arc or rifting setting.