scholarly journals Structural geology and regional tectonic significance of the Ramgarh thrust, Himalayan fold-thrust belt of Nepal

Tectonics ◽  
2005 ◽  
Vol 24 (4) ◽  
pp. n/a-n/a ◽  
Author(s):  
Ofori N. Pearson ◽  
Peter G. DeCelles
Keyword(s):  
Structural Geology ◽  
Thrust Belt ◽  
Tectonic Significance ◽  
Ramgarh Thrust ◽  
Regional Tectonic

The Blind Creek Limestone, Keremeos, British Columbia: Structure and Regional Tectonic Significance

1975 ◽  
Vol 12 (11) ◽  
pp. 1929-1933
Author(s):  
W. C. Barnes ◽  
J. V. Ross
Keyword(s):  
British Columbia ◽  
Compressive Stress ◽  
Ductile Deformation ◽  
Large Block ◽  
Stress Direction ◽  
Upper Paleozoic ◽  
Tectonic Significance ◽  
Regional Tectonic ◽  
Similar Body ◽  
Paleozoic Rocks

A large block of Upper Paleozoic limestone at Blind Creek near Keremeos, B.C. was emplaced by dry gravity sliding, probably associated with uplift related to nearby Eocene volcanism. The block is a nearly flat tabular unit, exposed over an area of 650 m by 1300 m, and is separated from underlying chaotic breccias derived from adjacent Paleozoic rocks and from Eocene volcanic flow rocks by a sole fault. The block comprises two lithologically and tectonically distinct units, a lower imbricated unit consisting of several slices repeating the same sequence of strata, separated from an upper unit of massive limestone by a low-angle fault. Within the imbricated unit, early faults emanate from lenticular masses of breccia along the sole, become increasingly steeper upward, and are truncated above by the upper low angle fault. Associated minor folds and fractures have a clockwise sense of rotation. Later fractures and associated minor folds have the opposite dip and sense of rotation. These two subsets comprise a conjugate set whose inferred compressive stress direction coincides with the present overall dip direction of the entire mass.The northwesterly adjacent autochthonous Olalla limestone, or a similar body now buried by younger units, is a likely source for the Blind Creek allochthon.Absence of any structures within the limestone indicative of ductile deformation contrasts markedly with those of the highly deformed rocks of the Old Tom and Shoemaker Formations, the Kobau Group, and the nearby gneisses of the western Shuswap Complex.

scholarly journals Petrogenesis of the Cretaceous Intraplate Mafic Intrusions in the Eastern Tianshan Orogen, NW China

2021 ◽  
Vol 9 ◽  
Author(s):  
Weifeng Zhang ◽  
Xin Deng ◽  
Bing Tu ◽  
Lianhong Peng ◽  
Xinbiao Jin
Keyword(s):  
Stability Field ◽  
Magma Evolution ◽  
Nd Isotope ◽  
Eastern Tianshan ◽  
Nw China ◽  
Late Mesozoic ◽  
Mafic Intrusions ◽  
Tectonic Significance ◽  
Regional Tectonic ◽  
Garnet Stability Field

In this study, we conducted zircon U-Pb dating, and whole-rock geochemical and Sr-Nd isotope analyses on the Late Mesozoic dolerite dykes in the Bailingshan Fe deposit (Eastern Tianshan Orogen, NW China) to unravel their petrogenesis and regional tectonic significance. Zircon U-Pb dating on the dolerite yielded an Early Cretaceous age of 129.7 ± 1.4 Ma. The dolerite is calc-alkaline sodic (Na2O/K2O = 4.71 to 6.80), and enriched in LILEs (Rb, K, Sr, and Pb) but depleted in HFSEs (Nb, Ta, and Ti). The intermediate Nb/U (16.7 to 18.5) and Ce/Pb (6.33 to 6.90) values, and the presence of xenocrystic zircons in these dolerite dykes suggest crustal assimilation during the magma evolution. Petrological modeling suggests fractionation of olivine, pyroxene, garnet, and spinel. All the dolerite samples have low initial 87Sr/86Sr (0.7041 to 0.7043) and positive εNd(t) (+ 4.6 to + 5.1) values, indicative of a depleted asthenospheric mantle source. Partial melting modeling suggests that the melting has occurred in the spinel-garnet stability field. Integrating the data from ore deposit geology, geochronology, geochemistry and Sr-Nd isotopes, we proposed that the Late Cretaceous Eastern Tianshan mafic magmatism was developed in an intraplate extension setting.

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