scholarly journals Jurassic Igneous Activity in the Yuseong Area on the Southern Margin of the Gyeonggi Massif, Korean Peninsula, and Its Implications for the Tectonic Evolution of Northeast Asia during the Jurassic

Minerals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 466
Author(s):  
Seung Hwan Lee ◽  
Chang Whan Oh ◽  
Soolim Jung
Keyword(s):  
Korean Peninsula ◽  
Tectonic Setting ◽  
Northeast Asia ◽  
Crustal Contamination ◽  
Igneous Rocks ◽  
Volcanic Arc ◽  
Southern Margin ◽  
Igneous Activity ◽  
Gyeonggi Massif ◽  
Okcheon Belt

Jurassic dioritic to granitic igneous rocks extensively intrude into the southern Korean Peninsula, including the Yuseong area located at the boundary between the southern margin of the Gyeonggi Massif and the northern margin of the Okcheon Belt. In this study, the petrogenesis and sources of Jurassic igneous rocks in the Yuseong area were investigated. The U–Pb zircon age data from the Jurassic plutonic rocks in the Yuseong area give two igneous ages, ca. 178–177 Ma and 169–168 Ma, indicating that two stages of igneous activity occurred in the Yuseong area during the Jurassic. The geochemical characteristics of Jurassic diorites indicate that they originated from enriched mid-ocean ridge basalt (E-MORB; Nb/Yb = 5.63–7.27; Zr/Yb = 118–156). The enriched Th/Yb ratios (5.5–8.0) in the diorites imply that they experienced crustal contamination during magma ascent. The Jurassic granitoids in the Yuseong area are divided into I- and S-type granites. The Jurassic I-type granitoids may have formed via the partial melting of mafic rocks with mixtures of 10–40% pelite-derived melt, while the S-type granites originated from felsic pelite. The Jurassic diorites have low Nb/Th ratios with depletion of the Nb and Ta components, indicating that they formed in a volcanic arc tectonic environment. On the other hand, the Jurassic granitoids show two different tectonic environments: a volcanic arc, and a syncollisional environment. The granites with syncollisional character are S-type granites, and may give incorrect information about tectonic setting because of the changes in the trace elements of the S-type granite due to fractional crystallization. Early Jurassic (200–190 Ma) igneous rocks are distributed only in the southeastern Korean Peninsula, including the Yeongnam Massif; Jurassic igneous rocks formed at ca. 190–180 Ma occur mainly in the Okcheon Belt and southern Gyeonggi Massif, which includes the Yuseong area. Middle Jurassic igneous rocks widely intruded from the Okcheon Belt, through the Gyeonggi and Nangrim massifs in the Korean Peninsula, to the Liaoning area in the North China Craton at 180–160 Ma. This distribution pattern of the Jurassic granitoids suggests that flat subduction started after 180 Ma in Northeast Asia.

Evolution of the Martian Crust

2017 ◽  
Author(s):  
John C. Bridges
Keyword(s):  
Plate Tectonics ◽  
Chemical Weathering ◽  
Compositional Data ◽  
Crustal Contamination ◽  
Planetary Science ◽  
Mantle Metasomatism ◽  
Igneous Rocks ◽  
Forthcoming Article ◽  
Physical Weathering ◽  
Igneous Activity

This is an advance summary of a forthcoming article in the Oxford Encyclopedia of Planetary Science. Please check back later for the full article.Mars, which has a tenth of the mass of Earth, has cooled as a single lithospheric plate. Current topography gravity maps and magnetic maps do not show signs of the plate tectonics processes that have shaped the Earth’s surface. Instead, Mars has been shaped by the effects of meteorite bombardment, igneous activity, and sedimentary—including aqueous—processes. Mars also contains enormous igneous centers—Tharsis and Elysium, with other shield volcanoes in the ancient highlands. In fact, the planet has been volcanically active for nearly all of its 4.5 Gyr history, and crater counts in the Northern Lowlands suggest that may have extended to within the last tens of millions of years. Our knowledge of the composition of the igneous rocks on Mars is informed by over 100 Martian meteorites and the results from landers and orbiters. These show dominantly tholeiitic basaltic compositions derived by melting of a relatively K, Fe-rich mantle compared to that of the Earth. However, recent meteorite and lander results reveal considerable diversity, including more silica-rich and alkaline igneous activity. These show the importance of a range of processes including crystal fractionation, partial melting, and possibly mantle metasomatism and crustal contamination of magmas. The figures and plots of compositional data from meteorites and landers show the range of compositions with comparisons to other planetary basalts (Earth, Moon, Venus). A notable feature of Martian igneous rocks is the apparent absence of amphibole. This is one of the clues that the Martian mantle had a very low water content when compared to that of Earth.The Martian crust, however, has undergone hydrothermal alteration, with impact as an important heat source. This is shown by SNC analyses of secondary minerals and Near Infra-Red analyses from orbit. The associated water may be endogenous.Our view of the Martian crust has changed since Viking landers touched down on the planet in 1976: from one almost entirely dominated by basaltic flows to one where much of the ancient highlands, particularly in ancient craters, is covered by km deep sedimentary deposits that record changing environmental conditions from ancient to recent Mars. The composition of these sediments—including, notably, the MSL Curiosity Rover results—reveal an ancient Mars where physical weathering of basaltic and fractionated igneous source material has dominated over extensive chemical weathering.

scholarly journals Petrogenesis of Volcanic Arc Granites from Bayah Complex, Banten, Indonesia

2019 ◽  
Vol 4 (2) ◽  
pp. 104
Author(s):  
Jemi Saputra Ahnaf ◽  
Aton Patonah ◽  
Haryadi Permana
Keyword(s):  
Tectonic Setting ◽  
Crustal Contamination ◽  
Polarized Light ◽  
Granitic Rocks ◽  
Tectonic Activity ◽  
Molar Ratio ◽  
Petrographic Analysis ◽  
Volcanic Arc ◽  
Regional Tectonic ◽  
Type Granite

This research aimed to reveal the petrogenesis of granitic rocks of Bayah Complex starting from magma differentiation to exposing event, this research also intended to determine the tectonic environment. The methods carried out in this research include field observation, petrographic analysis using polarized light microscopy, and geochemical analysis using X-Ray Fluorescence (XRF) and Inductively Coupled Mass Spectrometry (ICP-MS). Petrographic analysis shows that Bayah granitic rocks are composed of quartz, plagioclase, and K-feldspar while the rest are amphibole, biotite, sericite, chlorite, epidote, and opaque. Based on its major oxide concentrations, Bayah granitic rocks classified as granite and diorite-quartz which have high-K calc-alkaline magma. 4 samples of granitic rocks showed the A/N+K+C > 1 molar ratios belonging to the peraluminous S-type granite index while the remaining 1 sample showed a molar ratio of A/N+ K+C < 1 and A/N+K > 1 which classified as metaluminous I-type granite. Accordingly, Bayah granitic rocks are S-type granite which crystallized from sediment-derived magma, the sediments itself estimated sourced from continental especially Malay Peninsula, Indonesian Tin Island, and Schwaner Mountains. During differentiation, the magma undergone crustal contamination reflected by the increase in both SiO2 0.51 wt% and Al2O3 1.95 wt%, and decrease in Fe2O3 + MgO 0.61 wt% from the pure composition of sediment-derived magma. Furthermore, the occurrence of crustal contamination also recognized from high concentrations of Rb and Ba which indicate the interaction of magma with the materials of continental crust. Regard to the exposing event, Bayah granitic rocks approximated to be exposed due to regional tectonic activity which caused Orogenesa I in the Early Oligocene to the Late Oligocene. Moreover, based on the plot of trace elements especially Rb, Y, Nb, Ta, and Yb on Harker and tectonic discriminant diagrams, Bayah granitic rocks are formed on volcanic-arc active continental margins in accordance with regional tectonic setting.           

The youngest Neoproterozoic mafic dyke suite in the Arabian Shield: mildly alkaline dolerites from South Jordan – their geochemistry and petrogenesis

2001 ◽  
Vol 138 (3) ◽  
pp. 309-323 ◽  
Author(s):  
G. JARRAR
Keyword(s):  
Tectonic Setting ◽  
Crustal Contamination ◽  
Spinel Lherzolite ◽  
Mafic Dyke ◽  
East African ◽  
Elemental Ratios ◽  
Mafic Dykes ◽  
Nubian Shield ◽  
Igneous Activity ◽  
Arabian Nubian Shield

The Arabian–Nubian Shield evolved through a sequence of tectonomagmatic cycles, which took place during Neoproterozoic time (1000–540 Ma). Dyke emplacement constitutes one of the conspicuous features of the Arabian–Nubian Shield, with mafic dykes being the most abundant. The investigated dykes represent the youngest Neoproterozoic mafic dykes and have been dated in Jordan at 545 ± 13 Ma. Geochemically the studied dykes are mildly alkaline, are enriched in large ion lithophile elements (LILE) and high field strength cations (HFSC), show moderate enrichment of REE, and lack Nb anomaly. These features are consistent with a predominantly extensional continental tectonic setting. Crystallization temperatures of the suite fall between 1050 and 800 °C to as low as 650 °C as deduced from pyroxene thermometry. The investigated dykes were derived from a metasomatized lithospheric mantle by 5 % modal batch partial melting of phlogopite-bearing spinel lherzolite, according to geochemical modelling. The intra-suite geochemical features are explicable by 64 % fractional crystallization of olivine, pyroxene, plagioclase and titanomagnetite and possibly other accessories like apatite at a later stage. The cumulate produced from this fractionation of the investigated dyke suite contributed to the formation of the mafic lower crust of the Arabian–Nubian Shield. Elemental ratios and petrographic evidence indicate possible minor crustal contamination of the suite. The youngest mafic dykes show striking geochemical similarities to the same generation of dolerite dykes in the adjacent countries, to transitional young basalt suites of the Main East African Rift, and to Quaternary Jordanian basalts. The youngest mafic dyke suite, the rhyolites of the Aheimir suite, and St Katherina rhyolites of Sinai represent the last igneous activity in the Arabian–Nubian Shield before the onset of the Cambrian at about 545 Ma ago.

scholarly journals Statherian (ca. 1714–1680 Ma) Extension-Related Magmatism and Deformation in the Southwestern Korean Peninsula and Its Geological Significance: Constraints from the Petrological, Structural, Geochemical and Geochronological Studies of Newly Identified Granitoids

Minerals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 557
Author(s):  
Byung-Choon Lee ◽  
Weon-Seo Kee ◽  
Uk-Hwan Byun ◽  
Sung-Won Kim
Keyword(s):  
Korean Peninsula ◽  
Tectonic Setting ◽  
Alkali Feldspar ◽  
Ductile Deformation ◽  
Southwestern Part ◽  
The North ◽  
Deformation Event ◽  
Geochemical Analyses ◽  
A Minor ◽  
T Values

In this study, petrological, structural, geochemical, and geochronological analyses of the Statherian alkali feldspar granite and porphyritic alkali feldspar granite in the southwestern part of the Korean Peninsula were conducted to examine petrogenesis of the granitoids and their tectonic setting. Zircon U-Pb dating revealed that the two granites formed around 1.71 Ga and 1.70–1.68 Ga, respectively. The results of the geochemical analyses showed that both of the granites have a high content of K2O, Nb, Ta, and Y, as well as high FeOt/MgO and Ga/Al ratios. Both granites have alkali-calcic characteristics with a ferroan composition, indicating an A-type affinity. Zircon Lu-Hf isotopic compositions yielded negative εHf(t) values (−3.5 to −10.6), indicating a derivation from ancient crustal materials. Both granite types underwent ductile deformation and exhibited a dextral sense of shear with a minor extension component. Based on field relationships and zircon U-Pb dating, it was considered that the deformation event postdated the emplacement of the alkali feldspar granite and terminated soon after the emplacement of the porphyritic alkali feldspar granite in an extensional setting. These data indicated that there were extension-related magmatic activities accompanying ductile deformation in the southwestern part of the Korean Peninsula during 1.71–1.68 Ga. The Statherian extension-related events are well correlated with those in the midwestern part of the Korean and eastern parts of the North China Craton.

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