The Zhaheba ophiolite complex in Eastern Junggar (NW China): Long lived supra-subduction zone ocean crust formation and its implications for the tectonic evolution in southern Altaids

2017 ◽  
Vol 43 ◽  
pp. 17-40 ◽  
Author(s):  
Jun Luo ◽  
Wenjiao Xiao ◽  
John Wakabayashi ◽  
Chunming Han ◽  
Ji'en Zhang ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Tectonic Evolution ◽  
Crust Formation ◽  
Ocean Crust ◽  
Ophiolite Complex ◽  
Nw China

Petrogenesis and tectonic evolution of the Palaeozoic to Mesozoic Niuxinshan granitoids in the North Qilian orogen, NW China

2021 ◽  
Author(s):  
Fan Yang ◽  
Fei Xue ◽  
M. Santosh ◽  
Zesheng Qian ◽  
Cun Zhang ◽  
...  
Keyword(s):  
Tectonic Evolution ◽  
Nw China ◽  
The North ◽  
Qilian Orogen ◽  
North Qilian

Melt Percolation, Melt-Rock Reaction and Oxygen Fugacity in Supra-Subduction Zone Mantle and Lower Crust from the Leka Ophiolite Complex, Norway

2021 ◽  
Author(s):  
Brian O’Driscoll ◽  
Julien Leuthold ◽  
Davide Lenaz ◽  
Henrik Skogby ◽  
James M D Day ◽  
...  
Keyword(s):  
Single Crystal ◽  
Subduction Zone ◽  
Oxygen Fugacity ◽  
Lower Crust ◽  
Oceanic Lithosphere ◽  
Ophiolite Complex ◽  
Global Comparison ◽  
Oceanic Spreading ◽  
Melt Percolation ◽  
Lower Crustal

Abstract Samples of peridotites and pyroxenites from the mantle and lower crustal sections of the Leka Ophiolite Complex (LOC; Norway) are examined to investigate the effects of melt-rock reaction and oxygen fugacity variations in the sub-arc oceanic lithosphere. The LOC is considered to represent supra-subduction zone (SSZ) oceanic lithosphere, but also preserves evidence of pre-SSZ magmatic processes. Here we combine field and microstructural observations with mineral chemical and structural analyses of different minerals from the major lithologies of the LOC. Wehrlite and websterite bodies in both the mantle and lower crust contain clinopyroxene likely formed at a pre-SSZ stage, characterised by high Al, high Cr, low Mg crystal cores. These clinopyroxenes also exhibit low Al, low Cr, high Mg outer rims and intracrystalline dissolution surfaces, indicative of reactive melt percolation during intrusion and disruption of these lithologies by later, SSZ-related, dunite-forming magmas. Chromian-spinel compositional variations correlate with lithology; dunite-chromitite Cr-spinels are characterised by relatively uniform and high TiO2 and Al2O3, indicating formation by melt-rock reaction associated with SSZ processes. Harzburgite Cr-spinel compositions are more variable but preserve a relatively high Al2O3, low TiO2 endmember that may reflect crystallisation in a pre-SSZ oceanic spreading centre setting. An important finding of this study is that the LOC potentially preserves the petrological signature of a transition between oceanic spreading centre processes and subsequent supra-subduction zone magmatism. Single crystal Cr-spinel Fe3+/ΣFe ratios calculated on the basis of stoichiometry (from electron microprobe [EPMA] and crystal structural [X-ray diffraction; XRD] measurements) correlate variably with those calculated by point-source (single crystal) Mössbauer spectroscopy. Average sample EPMA Fe3+/ΣFe ratios overestimate or underestimate the Mössbauer-derived values for harzburgites, and always overestimate the Mössbauer Fe3+/ΣFe ratios for dunites and chromitites. The highest Fe3+/ΣFe ratios, irrespective of method of measurement, are therefore generally associated with dunites and chromitites, and yield calculated log(fO2)FMQ values of up to ~+1.8. While this lends support to the formation of the dunites and chromitites during SSZ-related melt percolation in the lower part of the LOC, it also suggests that these melts were not highly oxidised, compared to typical arc basalts (fO2FMQ of >+2). This may in turn reflect the early (forearc) stage of subduction zone activity preserved by the LOC and implies that some of the arc tholeiitic and boninitic lava compositions preserved in the upper portion of the ophiolite are not genetically related to the mantle and lower crustal rocks, against which they exhibit tectonic contacts. Our new data also have implications for the use of ophiolite chromitites as recorders of mantle oxidation state through time; a global comparison suggests that the Fe3+/ΣFe signatures of ophiolite chromitites are likely to have more to do with local environmental petrogenetic conditions in sub-arc systems than large length-scale mantle chemical evolution.

scholarly journals Magnetotelluric imaging of a fossil paleozoic intraoceanic subduction zone in western Junggar, NW China

2016 ◽  
Vol 121 (6) ◽  
pp. 4103-4117 ◽  
Author(s):  
Yixian Xu ◽  
Bo Yang ◽  
Sheng Zhang ◽  
Ying Liu ◽  
Lupei Zhu ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Nw China ◽  
Magnetotelluric Imaging

Tectonic evolution of the Paleozoic Barluk continental arc, West Junggar, NW China

2018 ◽  
Vol 160 ◽  
pp. 48-66 ◽  
Author(s):  
Chu Wu ◽  
Tao Hong ◽  
Xing-Wang Xu ◽  
Ming-Jian Cao ◽  
Hao Li ◽  
...  
Keyword(s):  
Tectonic Evolution ◽  
Nw China ◽  
Continental Arc ◽  
West Junggar

Revisiting to the Neoproterozoic tectonic evolution of the Tarim Block, NW China

2021 ◽  
Vol 352 ◽  
pp. 106013
Author(s):  
Guang-You Zhu ◽  
Zhi-Yong Chen ◽  
Wei-Yan Chen ◽  
Hui-Hui Yan ◽  
Peng-Hui Zhang
Keyword(s):  
Tectonic Evolution ◽  
Nw China ◽  
Tarim Block
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