Petrogenesis and tectonic setting of Late Devonian high-Mg andesites in the Beishan orogen, NW China

2021 ◽  
pp. 1-16
Author(s):  
Guo-Qiang Wang ◽  
Xiang-Min Li ◽  
Ji-Yuan Yu ◽  
Tao Bu ◽  
Bo-Tao Huang ◽  
...  
Keyword(s):  
Middle Devonian ◽  
Plate Tectonics ◽  
Tectonic Setting ◽  
Late Devonian ◽  
Nd Isotope ◽  
Central Asian ◽  
Mantle Peridotites ◽  
Regional Tectonic ◽  
Southern Central ◽  
Early Late

Abstract High-Mg andesites (HMAs) are crucial for the reconstruction of plate tectonics, continental margin formation and lithospheric evolution. In this study, we present new fossil age, whole-rock geochemical and Sr–Nd isotope data on the newly discovered Dundunshan Group HMAs in the Dundunshan area of the Beishan orogen (central-southern Central Asian Orogenic Belt). The Dundunshan HMA samples are characterized by high MgO (6.47–7.02 wt%) contents and high Mg# values (67.27–68.77), with SiO2 (58.57–62.13 wt%), Al2O3 (14.49–16.07 wt%) and CaO (5.05–6.24 wt%) resembling typical HMAs. The Dundunshan HMA samples are calc-alkaline and strongly enriched in light rare earth elements (LREEs) and large-ion lithophile elements (LILEs), with slightly negative Eu anomaly and high-field-strength element (HFSE) depletions. Their (87Sr/86Sr)i ratios (0.7041–0.7057) and ϵNd(t) (3.73–5.59) indicate that the Dundunshan HMAs were mainly formed by the interactions between subducted oceanic sediment-derived melts and mantle peridotites. Fossil evidence and published radiometric age data constrain the formation of the Dundunshan HMAs to early Late Devonian time. Sedimentological features of the Middle Devonian Sangejing Formation and regional tectonic correlation suggest that the Hongliuhe–Niujuanzi–Xichangjing Ocean in the Dundunshan area was likely closed during late Middle Devonian time, and that the Dundunshan HMAs were formed in a post-collision extensional setting.

Early Permian to Late Triassic tectonics of the southern Central Asian Orogenic Belt: geochronological and geochemical constraints from gabbros and granites in the northern Alxa area, NW China

2020 ◽  
Vol 157 (12) ◽  
pp. 2089-2105
Author(s):  
Run-Wu Li ◽  
Xin Zhang ◽  
Qiang Shi ◽  
Wan-Feng Chen ◽  
Yi An ◽  
...  
Keyword(s):  
Tectonic Setting ◽  
Orogenic Belt ◽  
Central Asian Orogenic Belt ◽  
Late Triassic ◽  
Magma Source ◽  
Nw China ◽  
The North ◽  
Central Asian ◽  
Depleted Mantle ◽  
Southern Central

AbstractSituated between the North China Craton to the east and the Tarim Craton to the west, the northern Alxa area in westernmost Inner Mongolia in China occupies a key location for interpreting the late-stage tectonic evolution of the southern Central Asian Orogenic Belt. New LA-ICP-MS zircon U–Pb dating results reveal 282.2 ± 3.9 Ma gabbros and 216.3 ± 3.2 Ma granites from the Yagan metamorphic core complex in northern Alxa, NW China. The gabbros are characterized by low contents of Si, Na, K, Ti and P and high contents of Mg, Ca, Al and Fe. These gabbros have arc geochemical signatures with relative enrichments in large ion lithophile elements and depletions in high field strength elements, as well as negative εNd(t) (−0.91 to −0.54) and positive εHf(t) (2.59 to 6.37) values. These features indicate that a depleted mantle magma source metasomatized by subduction fluids/melts and contaminated by crustal materials was involved in the processes of magma migration and emplacement. The granites show high-K calc-alkaline and metaluminous to weakly peraluminous affinities, similar to A-type granites. They have positive εNd(t) (1.55 to 1.99) and εHf(t) (5.03 to 7.64) values. These features suggest that the granites were derived from the mixing of mantle and crustal sources and formed in a postcollisional tectonic setting. Considering previous studies, we infer that the final closure of the Palaeo-Asian Ocean in the central part of the southern Central Asian Orogenic Belt occurred in late Permian to Early–Middle Triassic times.

Provenance and tectonic setting of late Paleozoic sedimentary rocks from the Alxa Tectonic Belt (NW China): Implications for accretionary tectonics of the southern Central Asian Orogenic Belt

2020 ◽  
Vol 133 (1-2) ◽  
pp. 253-276
Author(s):  
Dongfang Song ◽  
Wenjiao Xiao ◽  
Brian F. Windley ◽  
Chunming Han
Keyword(s):  
Tectonic Setting ◽  
Sedimentary Rocks ◽  
Orogenic Belt ◽  
Central Asian Orogenic Belt ◽  
Late Paleozoic ◽  
Early Triassic ◽  
Central Asian ◽  
Southern Central ◽  
T Values ◽  
Tectonic Belt

Abstract The Central Asian Orogenic Belt has long been considered the largest Phanerozoic accretionary orogen in the world; it developed through the subduction and final closure of the Paleo–Asian Ocean. However, the architecture and duration of the accretionary orogenesis of the Central Asian Orogenic Belt are still controversial despite decades of investigation. In this study, we present field, compositional, and stratigraphically controlled detrital zircon geochronological data for late Paleozoic sedimentary rocks from the Alxa Tectonic Belt to constrain their provenance, tectonic setting, and the overall tectonic configuration of the southern Central Asian Orogenic Belt. A Devonian sample yields a unimodal age peak (ca. 424 Ma) and broad late Mesoproterozoic ages. A Carboniferous sample has Early Silurian (ca. 438 Ma) and Late Devonian (ca. 382 Ma) peaks along with Neoproterozoic to Archean ages. The Permian samples are dominated by Ordovician–Devonian and Carboniferous–Permian ages. They yield maximum depositional ages ranging from ca. 291 Ma to 248 Ma and contain abundant zircon ages that are close to their depositional ages. These data reveal Ordovician–Silurian and Carboniferous–Permian magmatic flare-ups separated by a Devonian magmatic lull in the southern Central Asian Orogenic Belt. The arc terranes in southern Mongolia, central Beishan, and northern Alxa provided major detritus for the late Paleozoic sediments. An abrupt shift of zircon εHf(t) values at ca. 400 Ma reveals significant late Paleozoic crustal growth and excludes southern Alxa as a source. Oceanic basins prevented detritus from southern Alxa from reaching northern Alxa during Permian–Early Triassic time. A geological and provenance comparison of Permian basins in the southern Central Asian Orogenic Belt reveals the existence of two separate forearcs ascribed to bipolar subduction of the Paleo–Asian Ocean. Combined with recent paleomagnetic data, this leads us to advocate for an archipelago-style accretionary process induced by subduction retreat for the late Paleozoic tectonic evolution of the southern Central Asian Orogenic Belt, which continued into Late Permian–Early Triassic.

Early–Middle Permian post-collisional granitoids in the northern Beishan orogen, northwestern China: evidence from U–Pb ages and Sr–Nd–Hf isotopes

2020 ◽  
Vol 57 (6) ◽  
pp. 681-697
Author(s):  
Min Li ◽  
Houtian Xin ◽  
Bangfang Ren ◽  
Yunwei Ren ◽  
Wengang Liu
Keyword(s):  
Northwestern China ◽  
Calc Alkaline ◽  
Nd Isotope ◽  
Central Asian ◽  
High K ◽  
Crustal Model ◽  
Lithospheric Extension ◽  
Southern Central ◽  
Crustal Origin ◽  
T Values

The geochemistry and Sr–Nd isotope, zircon U–Pb, and zircon Hf isotope compositions are reported for monzogranites and granodiorites from the Hazhu area in the northern Beishan orogen, northwestern China. Zircon U–Pb dating yielded ages of 270.1 ± 1.1 and 277.4 ± 1.2 Ma for the monzogranites and 263.6 ± 1.2 and 262.2 ± 1.1 Ma for the granodiorites. These monzogranites and granodiorites are metaluminous to weakly peraluminous I-type and belong to mid-K calc-alkaline and high-K calc-alkaline series. They exhibit high Mg# values and moderate degrees of differentiation (D.I. = 70.7–88.1). They are enriched in large-ion lithophile elements and light rare earth elements and depleted in high field strength elements. They show high (87Sr/86Sr)i ratios of 0.6995–0.7070 and high εNd(t) values of 4.37–5.70 with Nd model ages (TDM) of 522–789 Ma, suggesting a juvenile crustal origin. Furthermore, their εHf(t) values are all positive, and Hf isotopic crustal model ages ([Formula: see text] = 394–1097 Ma) also indicate a juvenile crustal origin. According to the data obtained in this study and other regional geological data acquired recently, the Hazhu granitoids were derived from common sources of melting from the Neoproterozoic to late Paleozoic juvenile crusts. The younger intrusions (granodiorites) are more basic, likely as a result of more juvenile lower crust being melted along with asthenospheric upwelling, which led to the addition of more basic components. These granitoids formed in a post-collisional setting. The tectonic regime transformed from an arc-related compressional setting to post-collisional extension, likely as a result of lithospheric extension and thinning in response to oceanic lithospheric delamination. These granitoids in the northern Beishan orogen were probably emplaced in a post-collisional extensional setting and suggest vertical continental crustal growth in the southern Central Asian Orogenic Belt.

Construction of Late Devonian Dundunshan arc in the Beishan orogen and its implication for tectonics of southern Central Asian Orogenic Belt

Lithos ◽  
2014 ◽  
Vol 184-187 ◽  
pp. 361-378 ◽  
Author(s):  
Qianqian Guo ◽  
Wenjiao Xiao ◽  
Quanlin Hou ◽  
Brian F. Windley ◽  
Chunming Han ◽  
...  
Keyword(s):  
Orogenic Belt ◽  
Central Asian Orogenic Belt ◽  
Late Devonian ◽  
Central Asian ◽  
Southern Central

Late Devonian–early Permian accretionary orogenesis along the North Tianshan in the southern Central Asian Orogenic Belt

2014 ◽  
Vol 57 (5-8) ◽  
pp. 1023-1050 ◽  
Author(s):  
Chao Li ◽  
Wenjiao Xiao ◽  
Chunming Han ◽  
Kefa Zhou ◽  
Ji’en Zhang ◽  
...  
Keyword(s):  
Orogenic Belt ◽  
Central Asian Orogenic Belt ◽  
Late Devonian ◽  
Early Permian ◽  
The North ◽  
Central Asian ◽  
Southern Central
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