Silicic volcanic rocks are associated with most, if not all, continental ×ood basalt provinces and volcanic rifted margins, where they can form substantial parts of the eruptive stratigraphy and have eruptive volumes >104 km3. Poor preservation of silicic volcanic rocks following kilometer-scale uplift and denudation of the volcanic rifted margins, however, can result in only deeper level struc...

Abstract The Mesoproterozoic MARA terrane of western South America is a composite igneous-metamorphic complex that important for Paleozoic paleogeographic reconstructions and the relative positions Laurentia Gondwana. magmatic detrital records are consistent with Laurentian origin; however, metamorphic deformation lack sufficient detail to constrain correlation units within timing mechanisms ac...

Introduction: It is generally accepted that in addition to igneous olivine grains, chondrules contain relict olivine grains that did not crystallize in situ [e.g., 1]. Chondrule melts cooled relatively fast [e.g., 2], which aided in the preservation of relict grains. One type of relict olivine grain, found both inside chondrules and as isolated olivine grains outside chondrules, and found both ...

Small-volume Late Cretaceous monogenetic alkaline volcanism along the southern margin of North America resulted in a broad igneous belt more than 1200 km long from the Trans Pecos region of west Texas to central Mississippi, collectively forming a northern Gulf of Mexico magmatic zone (NGMMZ). The locus of igneous activity is associated with the discontinuity separating Mesoproterozoic cratonic...

 Igneous Rocks form from the solidification of molten rock. Intrusive igneous rocks are composed of crystals that are large enough to be seen with the naked eye because these rocks cooled slowly, deep within the Earth thereby allowing time for the crystals to grow. In contrast, extrusive (volcanic) igneous rocks cool very quickly after they erupt from a volcano, and so are composed of microsco...

The composition of igneous rocks in the continental crust has changed throughout Earth's history. However, the impact of these compositional variations on chemical weathering, and by extension on seawater and atmosphere evolution, is largely unknown. We use the strontium isotope ratio in seawater [(87Sr/86Sr)seawater] as a proxy for chemical weathering, and we test the sensitivity of (87Sr/86Sr...

anomolously low A1203, low Ti02 and are enriched in chromium and nick~A We present petrographic and chemical c ata on the Kamloops Lake picritic tmalts as we1 I as the stratigraphic setting for thwe ultramafic lavas. Age constraints derive From field relationships, Mineral chemistry indicates th 31 these ultramafic rocks represent mantle-deri.ed material which has undergone: minimal differentia...