LP/HT metamorphic rocks in Wulan County, Qinghai Province: An Early Paleozoic paired metamorphic belt on the northern Qaidam Basin?

2015 ◽  
Vol 60 (35) ◽  
pp. 3501-3513 ◽  
Author(s):  
LiangChao DA ◽  
Zhen YAN ◽  
Yu HAN ◽  
XiuCai LI ◽  
YuSong WANG ◽  
...  
Keyword(s):  
Qaidam Basin ◽  
Metamorphic Rocks ◽  
Early Paleozoic ◽  
Metamorphic Belt ◽  
Qinghai Province

scholarly journals Geodynamic environments of the origin of poly- and monometamorphic complexes in the Southern Altai metamorphic belt, Central Asian orogenic belt

2019 ◽  
Vol 27 (3) ◽  
pp. 233-257
Author(s):  
I. K. Kozakov ◽  
A. M. Kozlovsky ◽  
V. V. Yarmolyuk ◽  
T. I. Kirnozova ◽  
M. M. Fugzan ◽  
...  
Keyword(s):  
Continental Margin ◽  
Active Continental Margin ◽  
Elevated Pressure ◽  
Metamorphic Rocks ◽  
Alkaline Magmatism ◽  
Spreading Ridge ◽  
High Grade ◽  
Early Paleozoic ◽  
Metamorphic Belt ◽  
Terrigenous Rocks

Tectonic sheets of various size along the southern slope of the Mongolian and Chinese Altai ranges and in eastern Kazakhstan include high-grade metamorphic rocks, which are collectively referred to as the Southern Altai Metamorphic Belt. Rocks of the sheets show traces of amphibolite-facies elevated-pressure metamorphism of the kyanite–sillimanite type M2. Some of the tectonic sheets display evidence of polymetamorphism: the rocks preserve textures and mineral assemblages of an earlier metamorphic episode (of elevated temperature and relatively low pressure) of the andalusite–sillimanite facies series M1. The earlier metamorphic episode occurred at 390–385 Ma, and the later one, at ~370–356 Ma. The protoliths of the high-grade metamorphic rocks were mostly Early Paleozoic terrigenous rocks and subordinate amounts of volcanic rocks analogous to the weakly metamorphosed or unmetamorphosed rocks in their northern surroundings. Typical rocks of the tectonic sheets are mafic dikes and massifs of the Gashun Nuur Complex, which were emplaced between metamorphic episodes M1 and M2. According to their geochemistry and Nd isotopic parameters, most of the metabasites are similar to enriched basalts of mid-oceanic ridges and oceans plateaus. The quantitatively subordinate group of the layered mafic bodies displays geochemical characteristics of subduction-related rocks. Correlations between the metamorphic events and magmatism in the continental (Mongolian and Chinese Altai) and paleoceanic (Trans-Altai Gobi and eastern Junggar) regions led us to suggest a geodynamic model for the development of the Southern Altai Metamorphic Belt. The volcano-terrigenous rocks, which were later metamorphosed, were accumulated mostly in the Early Paleozoic as an accretion wedge on an active continental margin. The earlier episode of high-temperature metamorphic M1 and coeval large-scale calc–alkaline magmatism occurred at the same active continental margin after the magmatic front shifted southward (in modern coordinates). The emplacement of the swarms of mafic bodies of the Gashun Nuur Complex and simultaneous rifting in the southern Chinese Altai were triggered by the subduction of an spreading ridge of an oceanic or backarc basin beneath the active margin. The second metamorphic episode (elevated-pressure metamorphism) M2 and overthrusting in the structures of the Altai are correlated with deformations at low angles and the transition from oceanic to continental volcanism in the Trans-Altai Gobi and Junggar. These tectonic processes were induced by the accretion of a system of mid-Paleozoic ensimatic island arcs of the Trans-Altai Gobi and Junggar to the Altai margin of the Siberian paleocontinent.

scholarly journals Provenance and tectonic significance of the Zhongwunongshan Group from the Zhongwunongshan Structural Belt in China: insights from zircon geochronology

2020 ◽  
Vol 12 (1) ◽  
pp. 25-43
Author(s):  
Yuan Peng ◽  
Yongsheng Zhang ◽  
Eenyuan Xing ◽  
Linlin Wang
Keyword(s):  
Detrital Zircon ◽  
Sedimentary Basin ◽  
Early Paleozoic ◽  
Granitic Gneiss ◽  
Metamorphic Belt ◽  
Early Devonian ◽  
Tectonic Environment ◽  
Tectonic Significance ◽  
North Qaidam ◽  
Back Arc

AbstractThe Zhongwunongshan Structural Belt (ZWSB) locates between the Olongbruk Microblock of North Qaidam and the South Qilian Block in China, and it has important implication for understanding the tectonic significance of North Qaidam. Nowadays, there are few discussion on the Caledonian tectonothermal events of the Zhongwunongshan Structural Belt, and there exist different opinions on provenance and tectonic environment of the Zhongwunongshan Group in the ZWSB and its adjacent North Qaidam. In this study, a comprehensive analysis of the detrital zircon geochronological research was carried out on the Zhongwunongshan Group. The detrital zircon U-Pb dating results showed two major populations. The first was Neoproterozoic (966-725 Ma) with a ∈Hf(t) = −15.9 to 9.5, and the other was late Early Paleozoic (460-434Ma) with a ∈Hf(t) = −9.6 to −3.1. In combination with previous research, the dominated provenances were found to be the Neoproterozoic granitic gneiss of the Yuqia-Shaliuhe HP-UHP metamorphic belt and the late Early Paleozoic granite of the Tanjianshan ophiolite-volcanic arc belt in North Qaidam. The Zhongwunongshan Group was deposited in the back-arc sedimentary basin related to the Caledonian collisional orogeny during Middle Silurian-Early Devonian (434-407.9 Ma).

scholarly journals Methanobacterium movens sp. nov. and Methanobacterium flexile sp. nov., isolated from lake sediment

2011 ◽  
Vol 61 (12) ◽  
pp. 2974-2978 ◽  
Author(s):  
Jinxing Zhu ◽  
Xiaoli Liu ◽  
Xiuzhu Dong
Keyword(s):  
Phylogenetic Analysis ◽  
16S Rrna ◽  
16S Rrna Gene ◽  
Type Strain ◽  
Qaidam Basin ◽  
Sequence Similarity ◽  
Single Cells ◽  
Rrna Gene ◽  
Qinghai Province ◽  
Gram Staining

Two mesophilic methanogenic strains, designated TS-2T and GHT, were isolated from sediments of Tuosu lake and Gahai lake, respectively, in the Qaidam basin, Qinghai province, China. Cells of both isolates were rods (about 0.3–0.5×2–5 µm) with blunt rounded ends and Gram-staining-positive. Strain TS-2T was motile with one or two polar flagella and used only H2/CO2 for growth and methanogenesis. Strain GHT was non-motile, used both H2/CO2 and formate and displayed a variable cell arrangement depending on the substrate: long chains when growing in formate (50 mM) or under high pressure H2 and single cells under low pressure H2. Phylogenetic analysis based on 16S rRNA gene sequences placed the two isolates in the genus Methanobacterium. Strain TS-2T was most closely related to Methanobacterium alcaliphilum NBRC 105226T (96 % 16S rRNA gene sequence similarity). Phylogenetic analysis based on the alpha subunit of methyl-coenzyme M reductase also supported the affiliation of the two isolates with the genus Methanobacterium. DNA–DNA relatedness between the isolates and M. alcaliphilum DSM 3387T was 39–53 %. Hence we propose two novel species, Methanobacterium movens sp. nov. (type strain TS-2T = AS 1.5093T = JCM 15415T) and Methanobacterium flexile sp. nov. (type strain GHT = AS 1.5092T = JCM 15416T).

Kinematics of rock flow and fabric development associated with shear deformation within the Zagros transpression zone, Iran

2011 ◽  
Vol 148 (5-6) ◽  
pp. 1009-1017 ◽  
Author(s):  
ALI FAGHIH ◽  
KHALIL SARKARINEJAD
Keyword(s):  
Deformation Zone ◽  
Pure Shear ◽  
Ductile Deformation ◽  
Metamorphic Rocks ◽  
Zagros Mountains ◽  
Metamorphic Belt ◽  
Kinematic Vorticity ◽  
Heterogeneous Nature ◽  
Thrust Sheets ◽  
Thrust System

AbstractThis paper presents quantitative data on the finite strain, quartz crystal fabric, geometry of flow and deformation temperatures in deformed quartzite samples to characterize the ductile deformation along the thrust sheets constituting the Sanandaj–Sirjan Metamorphic Belt within the Zagros Mountains of Iran. The results of this study emphasize the heterogeneous nature of deformation in this belt, showing a spatial variation in strain magnitude and in degree of non-coaxiality. A dominant top-to-the-SE sense of shear is indicated by the asymmetry of microstructures and quartz c-axis fabrics. Quartz c-axis opening angles suggest deformation temperatures range between 435° ± 50°C and 510° ± 50°C, which yield greenschist to amphibolite facies conditions during the ductile deformation. Mean kinematic vorticity number (Wm) measured in the quartzite samples ranges between 0.6 and 0.9 with an average of 0.76, which indicates that extrusion of the metamorphic rocks of the region was facilitated by a significant component of pure shear strain. Traced towards the basal thrust of the Zagros Thrust System from northeast to southwest, the quartz grain fabrics change from asymmetric cross-girdle fabrics in the internal part of the deformation zone to an asymmetric single-girdle fabric at distances close to the basal thrust. This variation may depend on the structural depth and on the geometry of the ductile deformation zone. The observed increase in strain and vorticity within the study area is comparable with patterns recorded within metamorphic rock extrusions within other orogens in the world.

scholarly journals Marivita lacus sp. nov., isolated from a saline lake

2015 ◽  
Vol 65 (Pt_6) ◽  
pp. 1889-1894 ◽  
Author(s):  
Zhi-Ping Zhong ◽  
Ying Liu ◽  
Ting-Ting Hou ◽  
Hong-Can Liu ◽  
Yu-Guang Zhou ◽  
...  
Keyword(s):  
Phylogenetic Trees ◽  
Saline Lake ◽  
Qaidam Basin ◽  
Sequence Similarity ◽  
Rrna Gene ◽  
Aerobic Bacterium ◽  
Respiratory Quinone ◽  
Qinghai Province ◽  
Gram Staining ◽  
Bacterium Strain

A Gram-staining-negative, strictly heterotrophic and aerobic bacterium, strain TS-T44T, was isolated from a saline lake, Tuosu Lake in Qaidam basin, Qinghai province, China. Its taxonomic position was investigated using a polyphasic approach. Cells of strain TS-T44T were non-endospore-forming, non-motile rods, 0.8–1.2 μm wide and 1.2–3.0 μm long. Catalase- and oxidase-positive. Growth occurred in the presence of up to 8  % (w/v) NaCl (optimum, 3.0  %) and at 15–35 °C (optimum, 25 °C) and pH 7.0–10.0 (optimum, pH 7.5–8.5). C18 : 1ω7c was the predominant fatty acid. The major respiratory quinone was Q-10. The major polar lipids were phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine, an unidentified aminolipid and an unknown lipid. The DNA G+C content was 65.5 mol% [determined from the melting temperature (Tm)]. Phylogenetic trees based on 16S rRNA gene sequences showed that strain TS-T44T was associated with the genus Marivita and showed highest sequence similarity to Marivita cryptomonadis CL-SK44T (97.7  %), Marivita litorea CL-JM1T (97.5  %) and Marivita geojedonensis DPG-138T (97.3  %), and < 97  % to other species. DNA–DNA relatedness of strain TS-T44T to M. cryptomonadis JCM 15447T, M. litorea JCM 15446T and M. geojedonensis KCTC 23882T was 23 ± 3  %, 33 ± 4  % and 35 ± 2  %, respectively. Based on the data presented, it is concluded that strain TS-T44T represents a novel species of the genus Marivita, for which the name Marivita lacus sp. nov. is proposed. The type strain is TS-T44T ( = CGMCC 1.12478T = JCM 19516T).

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