نتایج جستجو برای: mafic composition
تعداد نتایج: 261231 فیلتر نتایج به سال:
Whether or not coarse detrital sedimentary rocks occur within the \3.7 Ga Isua Greenstone Belt (IGB), southern west Greenland, has been debated for some time. Repeated, regional metamorphic, deformational, and metasomatic events have obscured most protolith lithologies leading to misunderstandings about the stratigraphy and environments of deposition. Rocks here interpreted as meta-conglomerate...
A common view of the thermal and shock histories of ordinary-chondrite (OC) parent bodies is that, for the most part, thermal and shock metamorphism were distinguishable and successive events; e.g., the decay of 26 Al heated chon-dritic planetesimals and subsequent impacts produced various shock effects. Although collisions have long been acknowledged as capable of producing significant heating...
Geochemical characteristics of greywacke and intercalated phyllites from Haveri and Dharwad block (long N 75° 10' to 75° 25' E and lat 15° 30' to 45° 00'S and (long 75° 05'E and lat S 15° 15' to 15° 35') of Shimoga basin have been studied to unravel the provenance and the tectonic setting of the greywackes. The greywackes are medium grained feldspatholithic and show presence of perthitic feldsp...
Microbial abundance and diversity in deep subsurface environments is dependent upon the availability of energy and carbon. However, supplies of oxidants and reductants capable of sustaining life within mafic and ultramafic continental aquifers undergoing low-temperature water-rock reaction are relatively unknown. We conducted an extensive analysis of the geochemistry and microbial communities r...
The Po-Adriatic region offers an excellent case for reconstructing sediment provenance and transport pathways of a multi-sourced sediment-routing system. Through comprehensive set ∼1400 geochemical data, model flux was built based on distinct compositional fingerprints 53 fluvial systems their comparison to coastal, shelf deep-marine sediments. Geochemically unique catchment lithologies (mafic/...
Analyses of outcrops created by the impact craters Endurance, Fram and Eagle reveal the broad lateral continuity of chemical sediments at the Meridiani Planum exploration site on Mars. Approximately ten mineralogical components are implied in these salt-rich silicic sediments, from measurements by instruments on the Opportunity rover. Compositional trends in an apparently intact vertical strati...
the study area is located about 3 km southwest of the hormoz island in the hormozgan province, in the persian gulf. the main rock units in the region consist of a highly altered acidic pluton cratophyre, which is responsible for apatite formation, diabasic dike, marl and altered basalt. apatite is the only phosphate mineral in the hormoz island, which has accumulated ree in its crystal structur...
Some 43 samples collected from surficial sediments of Semnan Province (Alborz zone) and NE Isfahan Province (Central Iran zone) were analyzed, for constrains on provenance. Sand fraction were analyzed by XRF analyzer Philips Model PW 2450 in the laboratory of the Geology Survey Iran (GSI). Precision was 0.01%. Furthermore, 8 selected sediment samples and 8 samples from rock units from surroundi...
Arc magmas and the continental crust share many chemical features, but a major question remains as to whether these features are created by subduction or are recycled from subducting sediment. This question is explored here using Th/La, which is low in oceanic basalts (<0 2), elevated in the continents (>0 25) and varies in arc basalts and marine sediments (0 09–0 34). Volcanic arcs form linear...
Acanthomorphic acritarch fossils, including some interpreted to be the fossils of the earliest animal embryos, first appear in the lower Doushantuo Formation of the Yangtze Gorges area (YGA). Further, the complete paleontological and geochemical record for the YGA has played a central role in defining the global biological and geochemical backdrop that presaged and witnessed the dawn of diverse...
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