scholarly journals LATERAL ZONALITY OF THE ANYUI SEGMENT OF THE CHUKCHI PLUTONIC BELT (WESTERN CHUKOTKA)

2021 ◽  
pp. 117-125
Author(s):  
VASILY EGOROVICH STRIKHA ◽  
Keyword(s):  
Early Cretaceous ◽  
Continental Margin ◽  
Active Continental Margin ◽  
Primitive Mantle ◽  
Southwestern Part ◽  
Mantle Enrichment ◽  
Plutonic Belt ◽  
Gold Bearing

Early Cretaceous granitoids of the Anyui segment of the Chukchi plutonic belt are represented by associations: gabbro-granite, monzodiorite-granite and granite-leucogranite. For the rocks of gabbro-granite and monzonite-granite associations with respect to the primitive mantle, enrichment of Cs, Rb, K was established, with depletion of Nb, Hf, Ti. Granitoids of the granite-leucogranite association are characterized by the most contrasting ratios of enriched and depleted elements, with deep lows of Ba, Nb, Sr, P, Ti against the background of high Cs, Rb, K, Th, U, as well as the absence of a minimum of Hf. Along with the presence of lateral zonality in the placement of granitoids in relation to the southwestern border of the Anyuy Terrain, these data suggest the subductive nature of the formation of gold-bearing gabbro-granite and monzonite-granite associations in the conditions of an active continental margin that arose in the southwestern part of the Chukchi Terrain in Early Cretaceous time due to subduction.

scholarly journals Sedimentary provenance study of the post-Early Permian to pre-Early Cretaceous metasedimentary Duque de York Complex, Chile

2010 ◽  
Vol 33 (2) ◽  
pp. 199
Author(s):  
Juan Pablo Lacassie ◽  
Francisco Herve ◽  
Barry Roser
Keyword(s):  
Early Cretaceous ◽  
Continental Margin ◽  
Active Continental Margin ◽  
Source Area ◽  
Mineralogical Composition ◽  
Late Triassic ◽  
Low Grade ◽  
Early Permian ◽  
Magmatic Arc ◽  
Geochemical Analyses

The Duque de York Complex constitutes a post-Early Permian to pre-Early Cretaceous metasedimentary succession that crops out at the Madre de Dios and Diego de Almagro archipelagos along the Chilean Patagonian Andes. The petrography and geochemistry of sandstones and mudstones of this complex have been analyzed to characterize its source and depositional tectonic regime. Sandstone modal compositions are dominated by feldspar and, in similar but smaller proportions, by quartz. The mineralogical composition of the sandstones and mudstones is compatible with a low-grade sub-greenschist facies metamorphism. This did not affect significantly the geochemical compositions of these rocks. Nevertheless, the geochemical analyses reveal variable K+ enrichment, especially in the mudstones. Chemical Index of Alteration values of the sandstones and mudstones range between 58 and 71, indicating that the sediment underwent moderate chemical alteration in the source area or during transportation. Sandstone modal compositions are consistent with erosion of the plutonic roots of a magmatic arc. Geochemical provenance indices suggest a relatively evolved source, close in composition to typical continental magmatic arc granodiorite. Deposition of the detritus is most likely to have occurred within an active continental margin. Geochronological, petrographic, and geochemical similarities between the metasediments of the Duke de York Complex, the LeMay Group (Western Antarctica) and the Permian-Late Triassic Rakaia terrane (New Zealand) suggest a common geodynamic set-up for these three successions. This likely constituted an extensive late Paleozoic-early Mesozoic active continental margin, possibly along the Antarctic sector of Gondwana.

scholarly journals Petrographical, geochemical characteristics and ironmineralization of mafic massif at Tan Hoa area of Tan Chau, Tay Ninh

2015 ◽  
Vol 18 (4) ◽  
pp. 67-83
Author(s):  
Cong The Nguyen ◽  
Hoang Kim Nguyen
Keyword(s):  
Trace Elements ◽  
Continental Margin ◽  
Spectroscopic Analysis ◽  
Active Continental Margin ◽  
Geochemical Characteristics ◽  
Primitive Mantle ◽  
Secondary Mineral ◽  
Accessory Minerals ◽  
Mineral Components

The mafic massif at Tan Hoa area, Tan Chau, Tay Ninh (Hill 95) was detected in 1986 and was classified as Tay Ninh complex (K1tn, Nguyen Ngoc Hoa et al, 1995). Petrographical composition of this complex was clarified through the bores in 2013. It included gabbrodiorite, gabbronorite, gabbro, gabbropyroxenite and pyroxenite. The main mineral components were plagioclase, clinopyroxene, orthopyroxene and green hornblende. The secondary mineral was biotite. The accessory minerals are apatite, sphene, magnetite, pyrrhotite. Tay Ninh complex was in high content of titanium, rich in elements of Fe, Ti, V but low content of Rb, Sr, Y, Cs, Ba, Sm, Eu, Nd. The rare and trace elements standardized with primitive mantle and chondrite showed that their origin was from the deep, clear mantle and classified in rift on active continental margin pattern. Tay Ninh complex was characterized by its high anomalies in geophysics. The results of chemical and spectroscopic analysis, grinding and ore selection offered prospect of iron and titanium mineralization for complex.

Nature and origin of the volcanic ash beds near the Permian–Triassic boundary in South China: new data and their geological implications

2019 ◽  
Vol 157 (4) ◽  
pp. 677-689 ◽  
Author(s):  
Binsong Zheng ◽  
Chuanlong Mou ◽  
Renjie Zhou ◽  
Xiuping Wang ◽  
Zhaohui Xiao ◽  
...  
Keyword(s):  
Trace Element ◽  
Continental Margin ◽  
South China ◽  
Volcanic Ash ◽  
Active Continental Margin ◽  
Main Body ◽  
Early Triassic ◽  
Late Permian ◽  
Triassic Boundary ◽  
Permian Triassic Boundary

AbstractPermian–Triassic boundary (PTB) volcanic ash beds are widely distributed in South China and were proposed to have a connection with the PTB mass extinction and the assemblage of Pangea. However, their source and tectonic affinity have been highly debated. We present zircon U–Pb ages, trace-element and Hf isotopic data on three new-found PTB volcanic ash beds in the western Hubei area, South China. Laser ablation inductively coupled plasma mass spectrometry U–Pb dating of zircons yields ages of 252.2 ± 3.6 Ma, 251.6 ± 4.9 Ma and 250.4 ± 2.4 Ma for these three volcanic ash beds. Zircons of age c. 240–270 Ma zircons have negative εHf(t) values (–18.17 to –3.91) and Mesoproterozoic–Palaeoproterozoic two-stage Hf model ages (THf2) (1.33–2.23 Ga). Integrated with other PTB ash beds in South China, zircon trace-element signatures and Hf isotopes indicate that they were likely sourced from intermediate to felsic volcanic centres along the Simao–Indochina convergent continental margin. The Qinling convergent continental margin might be another possible source but needs further investigation. Our data support the model that strong convergent margin volcanism took place around South China during late Permian – Early Triassic time, especially in the Simao–Indochina active continental margin and possibly the Qinling active continental margin. These volcanisms overlap temporally with the PTB biocrisis triggered by the Siberian Large Igneous Province. In addition, our data argue that the South China Craton and the Simao–Indochina block had not been amalgamated with the main body of Pangea by late Permian – Early Triassic time.

Evolution of an active continental margin as exemplified by the Alpine history of the Caucasus

1977 ◽  
Vol 40 (3-4) ◽  
pp. 183-199 ◽  
Author(s):  
Sh.A. Adamia ◽  
M.B. Lordkipanidze ◽  
G.S. Zakariadze
Keyword(s):  
Continental Margin ◽  
Active Continental Margin ◽  
The Caucasus ◽  
History Of
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