Genesis and tectonic setting of Middle Permian OIB-type mafic rocks in the Sumdo area, southern Lhasa terrane

Lithos ◽  
2019 ◽  
Vol 324-325 ◽  
pp. 429-438 ◽  
Author(s):  
Bin Wang ◽  
Chao-Ming Xie ◽  
Jian-Jun Fan ◽  
Ming Wang ◽  
Yun-Peng Yu ◽  
...  
Keyword(s):  
Tectonic Setting ◽  
Middle Permian ◽  
Mafic Rocks ◽  
Lhasa Terrane

scholarly journals Permian Triassic geologic evolution in the southern Kitakami Belt, Japan

1992 ◽  
Vol 6 ◽  
pp. 155-155
Author(s):  
Kotaro Kamada
Keyword(s):  
Middle Triassic ◽  
Sedimentary Basin ◽  
Tectonic Setting ◽  
Japan Sea ◽  
Passive Margin ◽  
Middle Permian ◽  
Asian Continent ◽  
Transform Faults ◽  
Magmatic Arc ◽  
The Japan Sea

Before opening of the Japan Sea, the Japanese islands were attached to the eastern margin of the Asian continent. The Southern Kitakami Belt is regarded as a micro-continent in an accretional complex of the islands, that accreted before the Early Cretaceous. But its tectonic setting and location between the belt and the Asian continent is still an unresolved argument.Permo-Triassic sequences in the Southern Kitakami Belt are composed of shallow to off-shore deposits. These deposits are composed of clastics, carbonates with volcaniclastics. But there was no volcanic activity in the belt in the Middle to Late Permian. From the viewpoint of the sedimentary character and history, the Middle Permian to Middle Triassic sequences differ from their previous and their following successions in the belt. And the sedimentary basin of Middle Permian to Middle Triassic was bounded by transform faults. Magmatic arc was replaced by passive margin as hinterland of the Southern Kitakami Belt during the Middle Permian to Middle Triassic. It means that the sedimentary basin moved from the margin of Yangtze Platform to Sino-Korean Platform at that time.

Magmatic record of continuous Neo-Tethyan subduction after initial India-Asia collision in the central part of southern Tibet

2020 ◽  
Author(s):  
Feng Huang ◽  
Tyrone O. Rooney ◽  
Ji-Feng Xu ◽  
Yun-Chuan Zeng
Keyword(s):  
Mantle Wedge ◽  
Leading Edge ◽  
Continental Collision ◽  
Southern Tibet ◽  
Mafic Rocks ◽  
Lhasa Terrane ◽  
Slab Breakoff ◽  
Geodynamic Processes ◽  
Generation Mechanisms ◽  
Transitional Phase

The Lhasa Terrane in southern Tibet is the leading edge of the Tibet-Himalaya Orogen and represents a fragmentary record of terminal oceanic subduction. Thus, it is an ideal region for studying magmatism and geodynamic processes that occurred during the transition from oceanic subduction to continental collision and/or oceanic slab breakoff. Here we examine a suite of early Cenozoic mafic rocks (ca. 57 Ma) within the central part of Lhasa Terrane, southern Tibet, which erupted during a transitional phase between the onset of India-Asia continental collision and Neo-Tethyan slab breakoff. These rocks display a geochemical affinity with magmas produced by fluid-fluxed melting of the mantle wedge within a subduction zone environment. The whole-rock element and Sr-Nd isotope compositions of these mafic rocks are similar to those of Cretaceous subduction-related magmatism in southern Tibet, demonstrating the sustained influence of the Neo-Tethys Ocean slab on the mantle wedge during the onset of the collision of India and Asia. The results of our geochemical forward modeling constrain the conditions of melt generation at depths of 1.3−1.5 GPa with significant fluid additions from the Neo-Tethyan slab. These results provide the first petrological and geochemical evidence that slab flux-related magmatism continued despite the commencement of continental collision. While existing studies have suggested that magmas were derived from melting of the Neo-Tethyan slab during this period, our new results suggest that additional magma generation mechanisms were active during this transitional phase.

Middle Permian adakitic granite dikes in the Sumdo region, central Lhasa terrane, central Tibet: Implications for the subduction of the Sumdo Paleo-Tethys Ocean

2021 ◽  
Vol 205 ◽  
pp. 104610
Author(s):  
Bin Wang ◽  
Chao-Ming Xie ◽  
Yong-sheng Dong ◽  
Jian-Jun Fan ◽  
Yun-Peng Yu ◽  
...  
Keyword(s):  
Middle Permian ◽  
Lhasa Terrane ◽  
Tethys Ocean ◽  
Central Tibet

Two phases of post-onset collision adakitic magmatism in the southern Lhasa subterrane, Tibet, and their tectonic implications

2019 ◽  
Vol 132 (7-8) ◽  
pp. 1587-1602
Author(s):  
Tian-Yu Lu ◽  
Zhen-Yu He ◽  
Reiner Klemd
Keyword(s):  
Rare Earth ◽  
Lower Crust ◽  
Tectonic Setting ◽  
Geochemical Data ◽  
Magma Source ◽  
New Mineral ◽  
Element Abundances ◽  
Lhasa Terrane ◽  
Adakitic Rocks ◽  
Two Phases

Abstract Abundant Neogene adakitic magmatism occurred in the southern Lhasa subterrane after the onset of the India–Asia collision while convergence continued. However, the tectonic setting and magmatic evolution of the adakitic rocks are still under discussion. This study includes new mineral chemical and whole-rock geochemical data as well as zircon U-Pb and Lu-Hf isotopes of adakitic intrusive rocks from the Gyaca and Nyemo locations in the southern Lhasa subterrane. Laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) zircon U-Pb dating yielded crystallization ages of ca. 30 Ma for the Gyaca and Nyemo monzogranite and ca. 15 Ma for the Nyemo granodiorite. Both have common chemical signatures such as low MgO and heavy rare earth element contents as well as low compatible element abundances, indicating that these rocks result from partial melting of thickened lower crust with residual eclogite and garnet amphibolite. Furthermore, these rocks are characterized by variable positive zircon εHf(t) values, suggesting a juvenile magma source with variable ancient crustal contributions. Taking previous data into account, the adakitic magmatism concurs with an early late Eocene to Oligocene (ca. 38–25 Ma) and a late Miocene (ca. 20–10 Ma) phase. The adakitic rocks of the two phases are characterized by different fractionation evolutions of light and medium rare earth elements. We propose that the early-phase adakitic rocks were generated by the anatexis of Lhasa terrane lower crust owing to crustal shortening and thickening subsequent to the onset of the India–Asia collision and the upwelling of hot asthenosphere beneath the Lhasa terrane caused by the break-off of the Neo-Tethyan oceanic slab. The latest phase of adakitic rocks, however, relates to upwelling asthenosphere following the delamination and/or break-off of the subducting Indian continental slab.

Generation of the 105–100 Ma Dagze volcanic rocks in the north Lhasa Terrane by lower crustal melting at different temperature and depth: Implications for tectonic transition

2019 ◽  
Vol 132 (5-6) ◽  
pp. 1257-1272 ◽  
Author(s):  
Yun-Chuan Zeng ◽  
Ji-Feng Xu ◽  
Feng Huang ◽  
Ming-Jian Li ◽  
Qin Chen
Keyword(s):  
Early Cretaceous ◽  
Lower Crust ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Geochemical Data ◽  
Lhasa Terrane ◽  
The North ◽  
Tectonic Transition ◽  
Group I ◽  
Group Ii

Abstract Successively erupted intermediate-felsic rocks with variations in their geochemical compositions indicate physical changes in lower-crust conditions, and the variations can provide important insights into the regional tectonic setting. What triggered the late Early Cretaceous tectonic transition of the central-north Lhasa Terrane remains controversial, hindering the understanding of the mechanisms behind the formation of the central Tibetan Plateau. The sodic Dagze volcanic rocks in the north Lhasa Terrane are characterized by high contents of SiO2 and Na2O, low contents of MgO, Fe2O3, and K2O, and low values of Mg#. However, the trace element compositions of the whole-rocks and their zircons allow the rocks to be divided into two groups. The Group I rocks (ca. 105 Ma) have higher contents of Sr and Ba, higher Sr/Y and La/Yb ratios, and lower contents of Y, Yb, Ti, and Zr than Group II rocks (ca. 100 Ma). Besides, the zircons from Group I rocks have higher values of Yb/Gd and U/Yb, lower values of Th/U, and lower Ti contents than the zircons from Group II rocks. However, the rocks of both groups have identical depleted whole-rock Sr-Nd and zircon Hf isotope values. The geochemical data indicate that rocks of both groups were generated by partial melting of a juvenile lower crust, but the differences in the two groups reflect a transition from deep-cold melting to relatively shallower-hotter melting in the period from ca. 105 to 100 Ma. This transition was synchronous with the rapid cooling of granitoids, topographic uplift, and the shutdown of magmatism in the central-north Lhasa Terrane, and followed by sedimentation and the resumption of magmatism in the south Lhasa Terrane. The above observations collectively indicate that the central-north Lhasa Terrane was under an extensional setting in late Early Cretaceous, and we tentatively suggest that it was in response to lithospheric drip during roll-back of the northward-subducting Neo-Tethyan oceanic plate.

scholarly journals Tectonic Evolution of the West Bogeda: Evidences from Zircon U-Pb Geochronology and Geochemistry Proxies, NW China

Minerals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 341
Author(s):  
Yalong Li ◽  
Wei Yue ◽  
Xun Yu ◽  
Xiangtong Huang ◽  
Zongquan Yao ◽  
...  
Keyword(s):  
Tectonic Evolution ◽  
Tectonic Setting ◽  
Continental Rift ◽  
Middle Permian ◽  
Upper Permian ◽  
Late Permian ◽  
Island Arcs ◽  
The West ◽  
Structural Deformations ◽  
Tian Shan

The Bogeda Shan (Mountain) is in southern part of the Central Asian Orogenic Belt (CAOB) and well preserved Paleozoic stratigraphy, making it an ideal region to study the tectonic evolution of the CAOB. However, there is a long-standing debate on the tectonic setting and onset uplift of the Bogeda Shan. In this study, we report detrital zircon U-Pb geochronology and whole-rock geochemistry of the Permian sandstone samples, to decipher the provenance and tectonic evolution of the West Bogeda Shan. The Lower-Middle Permian sandstone is characterized by a dominant zircon peak age at 300–400 Ma, similar to the Carboniferous samples, suggesting their provenance inheritance and from North Tian Shan (NTS) and Yili-Central Tian Shan (YCTS). While the zircon record of the Upper Permian sandstone is characterized by two major age peaks at ca. 335 Ma and ca. 455 Ma, indicating the change of provenance after the Middle Permian and indicating the uplift of Bogeda Shan. The initial uplift of Bogeda Shan was also demonstrated by structural deformations and unconformity occurring at the end of Middle Permian. The bulk elemental geochemistry of sedimentary rocks in the West Bogeda Shan suggests the Lower-Middle Permian is mostly greywacke with mafic source dominance, and tectonic setting changed from the continental rift in the Early Permian to post rift in the Middle Permian. The Upper Permian mainly consists of litharenite and sublitharenite with mafic-intermediate provenances formed in continental island arcs. The combined evidences suggest the initial uplift of the Bogeda Shan occurred in the Late Permian, and three stages of mountain building include the continental rift, post-rift extensional depression, and continental arc from the Early, Middle, to Late Permian, respectively.

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