Hydrothermal alteration effects in geochemistry and Sr, Nd, Pb, and O isotopes of magmas from the Los Azufres geothermal field (Mexico): A statistical approach

Abstract

We present new major and trace elements and Sr, Nd, Pb, and O isotopic data on basaltic andesite to rhyolitic volcanic rocks from surface outcrops as well as drill wells from the Los Azufres geothermal field (LAGF). With a total installed capacity for electricity production of about 100 MW, LAGF is the second most important geothermal field in Mexico. Hydrothermal alteration has affected most subsurface (drill well) rocks, ranging from partial to complete alteration. The alteration mineralogy with increasing depth (and temperature) is: argillitization/silicification, zeolite/calcite formation, sericitization/chloritization, chloritization/epidotization. The Sr, Nd and Pb isotopic ratios from the LAGF show the following ranges: for surface rocks (87 Sr/ 86 Sr) i ª 0.70344-0.7048; (143 Nd/ 144 Nd) i ª 0.

Effect of Alteration Zones on Water Quality: A Case Study from Biga Peninsula, Turkey

“…These fluids then alter other rocks, changing their mineralogy and chemical composition (Nicholson 1993;Verma et al 2005;Pandarinath et al 2008). Complex zoned alteration patterns have been well documented from a large number of important hydrothermal ore deposit types, including submarine-volcanogenic massive sulphide (Finlow-Bates and Stumpfl 1981;MacLean and Kranidiotis 1987), mesothermal Au (Kerrich and Fyfe 1981;Neall and Phillips 1987;Böhlke 1989;Piantone et al 1994), porphyry copper (Lowell and Guilbert 1970;Hedenquist and Richards 1998), and epithermal Au-(Ag) deposits (Arribas 1995;Hedenquist and Arribas 1999).…”

“…These fluids then alter other rocks, changing their mineralogy and chemical composition (Nicholson 1993;Verma et al 2005;Pandarinath et al 2008). Complex zoned alteration patterns have been well documented from a large number of important hydrothermal ore deposit types, including submarine-volcanogenic massive sulphide (Finlow-Bates and…”

Zircon U-Pb geochronology, Sm-Nd and Pb-Pb isotope systematics of Ediacaran post-collisional high-silica Acampamento Velho volcanism at the Tupanci area, NW of the Sul-Rio-Grandense Shield, Brazil

“…The high 147 Sm/ 144 Nd ratios of the low-Ti rocks coupled to the REEchondrite normalized pattern observed is a feature produced in ultra-evolved silicic magmas attributed to magmatic fractionation, which may lead to an erroneous estimate of the Nd model age of the low-Ti rocks. Another possible explanation for the high 147 Sm/ 144 Nd in the low-Ti group could be related to a local source control, mineral sorting, with fractionation of minerals such as monazite, or hydrothermal alteration (Verma et al 2005). Nevertheless, the similarity between εNd(t) for both rhyolite groups suggest a similar source, which may be a paleoproterozoic crust, as evidenced by the 143 Nd/ 144 Nd vs. time diagram.…”

Genetic implications of new Sr and Nd isotopic data of the intrusive rocks from the Laramide Arc in Northern Sonora, Mexico.

“…In the Caborca region (at El Antimonio area), the Triassic-Jurassic sedimentary rocks exhibit marine signature and were deposited over paleozoic platform rocks (White and Guiza, 1949;González-León, 1997;González-León et al, 2005). A Jurassic volcanic arc composed of andesites, tuffs and rhyolites, occasionally metamorphosed to greenschist facies, is well documented in the Sonoran desert between Santa Ana and Sonoyta (Anderson and Silver, 1979;Corona, 1979), as well as in Cananea (Valentine, 1936;Wodzicki, 1995). Sedimentary rocks of Lower Cretaceous age are well developed in Sahuaripa, Cerro de Oro, Arizpe and Cananea (Rangin, 1982;Pubellier et al, 1995;Jacques-Ayala, 1995;González-León et al, 2000).…”