نتایج جستجو برای: type flood basalts
تعداد نتایج: 1365507 فیلتر نتایج به سال:
Large igneous provinces (LIPs) are a continuum of voluminous iron and magnesium rich rock emplacements which include continental flood basalts and associated intrusive rocks, volcanic passive margins, oceanic plateaus, submarine ridges, seamount groups, and ocean basin flood basalts. Such provinces do not originate at "normal" seafloor spreading centers. We compile all known in situ LIPs younge...
E xtinctions have played an important role in the history of life by clearing out niches and fostering adaptive radiations. Major mass extinctions involving 70% to more than 90% of extant species occurred at least five times during the last 540 million years. The discovery by Alvarez et al. (1) that the end-Cretaceous (65 Mya) mass extinction coincided with evidence for the impact of an asteroi...
11 Most mass extinctions during the last 500 m.y. coincide with eruptions of large igneous 12 provinces (LIP): the Cretaceous-Tertiary extinction was synchronous with the Deccan 13 flood volcanism, Permian-Triassic extinction with the eruption of the enormous 14 Siberian Traps, and End-Guadalupian extinction with the Emeishan volcanic province. 15 The causal link remains disputed, however, and ...
Massive continental volcanism and/or bolide impacts are considered by many authors to have caused three major mass extinction events during the last 300 million years: the end-Permian, end-Cretaceous and end-Triassic extinctions. However, reevaluation of the frequency of bolide impacts and plume-related flood basalt provinces indicates that both types of event occur much more frequently than ma...
Introduction: An abundance of geomorphological, mineralogical and geochemical evidence suggests widespread aqueous activity on the surface or early Mars [13]. However, recent studies of Mars’ early climate, using sophisticated three-dimensional climate models, find average surface temperatures too low to explain the observations [4,5]. It seems likely, therefore, that Mars’ early climate was, o...
We report isotopic and chemical compositions of unusual tridymite–hercynite xenoliths in middle Miocene Niutoushan tholeiites from the southeast coastal area of China. These xenoliths are characterized by positive cerium (Ce) anomalies and extremely high Al2O3 (32–34 wt.%) and total iron oxide (20–22%). They have Sr/Sr of 0.7050–0.7058, eNd(0) values of + 3.2 to + 4.2, Pb/Pb ratios of 18.8–19.1...
Pahoehoe lava flows are common in every basaltic province, and their submarine variants, pillow lavas and sheet flows, cover the bulk of the Earth. Pahoehoe flows are emplaced by inflation—the injection of molten lava underneath a solidified crust. Only in the past few years has an understanding of the inflation process and the ability to recognize ancient inflated lava flows been achieved. All...
[1] A global compilation of 170 time-averaged volumetric volcanic output rates (Qe) is evaluated in terms of composition and petrotectonic setting to advance the understanding of long-term rates of magma generation and eruption on Earth. Repose periods between successive eruptions at a given site and intrusive:extrusive ratios were compiled for selected volcanic centers where long-term (>10 yea...
The question of whether basaltic rocks in continental flood basalt provinces are primary magmas or whether they are descended in general from picritic parent magmas is reviewed. It is suggested that the latter is more likely to be correct on the evidence of phase relations and the relative rareness of mantle materials with appropriate Fe/Mg ratios. Major element variations in the residual liqui...
نمودار تعداد نتایج جستجو در هر سال
با کلیک روی نمودار نتایج را به سال انتشار فیلتر کنید