The hydrothermal alteration of oceanic basalts by seawater

Geology and geochemistry of the ophiolitic Trinity Terrane, California: Evidence of middle Paleozoic depleted supra-subduction zone magmatism in a proto-arc setting

“…Two major types of alteration are recognized from ophiolite and deep-sea studies, both types presumably related to hydrothermal circulation of seawater near mid-ocean spreading centers (Humphris and Thompson, 1978;Harper et al, 1988;Valsami and Cann, 1992). Downward flowing cold seawater depletes crustal rocks in CaO while producing enrichments in MgO.…”

“…Downward flowing cold seawater depletes crustal rocks in CaO while producing enrichments in MgO. This compositional shift results in chlorite-rich, amphibole-and epidote-poor assemblages (Humphris and Thompson, 1978). Hot, upwelling, Ca-rich fluids produce pipes of epidosite, a Ca-rich, Mg-poor rock composed essentially of nothing but epidote and quartz.…”

Adsorption of nucleotides onto ferromagnesian phyllosilicates: Significance for the origin of life

“…These phyllosilicates are aluminum-rich and unlikely to be abundant in the primitive altered oceanic crust of the Hadean. The Hadean seafloor was mainly formed of mafic and ultramafic rocks, such as basalt, komatiite and peridotite, which hydrothermal alteration has been widely studied through (i) petrological and mineralogical observations of samples collected in oceanic hydrothermal settings (Alt and Honnorez, 1984;Buatier et al, 1993;Hunter et al, 1999;Buatier et al, 2001;Alt and Teagle, 2003;Dias and Barriga, 2006;Lackschewitz et al, 2006;Mas et al, 2008); (ii) experimental alteration of bulk rocks (Humphris, 1978;Mottl and Holland, 1978;Mottl et al, 1979;Seyfried and Bischoff, 1979;Seyfried and Dibble, 1980;Seyfried and Bischoff, 1981;Seyfried and Mottl, 1982;Marcaillou, 2011;Lazar et al, 2012); and (iii) mineral evolution (Hazen et al, 2008;Hazen and Sverjensky, 2010;Hazen, 2013;Hazen et al, 2013). All above studies suggested that Fe-Mg rich phyllosilicates along with various oxides, hydroxides, anhydrites and sulfides are the major alteration minerals formed.…”

Petrogenesis and tectonic settings of volcanic rocks of the Ashele Cu–Zn deposit in southern Altay, Xinjiang, Northwest China: Insights from zircon U–Pb geochronology, geochemistry and Sr–Nd isotopes

“…The initial concentrations of some mobile elements, including U, Ca, Na, and LILEs (e.g., Ba, Rb, Sr and K), were likely to have been affected by alteration or metamorphism (Humphris and Thompson, 1978;Arndt, 2003;Wang et al, 2011b). However, the Rb and Ba contents and e Nd (t) values in the rocks show no obvious trend with increasing LOI, indicating that their abundances have not been changed by alteration.…”