Formation of Clay Minerals in Hydrothermal Environments

Abstract

Formation of clay minerals under hydrothermal influence is the result of rock alteration by circulating hot water in the Earth's crust. A pre-existing rockforming mineral assemblage is altered to a new set of minerals which are more stable under the hydrothermal conditions of temperature, pressure, and fluid composition. The interaction of hot water and rocks forms a spatially and temporally regular zonal pattern of new clay minerals, as the fluid with cooling temperature moves through the surrounding rock mass. This chapter discusses the formation of clay minerals in such dynamic processes of hydrothermal alteration. The approach is one of clay-mineral facies formed under conditions of massive alteration in the rocks. The chemical and mineralogical changes which occur on the scale of a rock or rock mass are considered to have been dealt with in the preceding chapter. The exact process of change via local, veininfluenced exchange processes is ignored for simplicity (see Chap. 6).Hydrothermal alteration is often accompanied by hydrothermal ore deposits and active geothermal systems which are of economic importance. A huge amount of field and laboratory data on alteration mineralogy and geochemistry have been accumulated through exploration of hydrothermal ore deposits and active geothermal fields due to the economic interest of this geologic process. Additionally, the amount of theoretical information pertaining to the hydrothermal alteration has been rapidly increasing in the last decade. These data have been reviewed from various aspects of interest, e.g. in connection with the geneses of porphyry copper deposits (Meyer and Hemley 1969; Rose and Burt 1979;Beane 1982), epithermal ore deposits (Hayba et al. 1985;Henley 1985;Heald et al. 1987;Shikazono 1988), geothermal systems associated with recent volcanism (Ellis and Mahon 1977;Browne 1978;Utada 1980;Henley and Ellis 1983), Kuroko deposits (Utada 1988), and hydrothermal systems at sea floor spreading centers (Rona et al. 1983, for a summary). In the present review, particular attention has been paid to the formation of clay minerals under these different hydrothermal environments.Initially, the general backgrounds of hydrothermal alteration will be briefly reviewed (Sect. 7.1). Section 7.2 is concerned with the terminology and definition of hydrothermal alteration. Sections 7.3 and 7.4 introduce the geo-B. Velde (ed.), Origin and Mineralogy of Clays

Illite occurrences related to volcanic-hosted hydrothermal mineralization in the Biga Peninsula, NW Turkey: Implications for the age and origin of fluids

“…Time has a negligible effect because the formation generally occurs during a short period (or short-lived geothermal systems; Jennings and Thompson, 1986;Ramseyer and Boles, 1986) and probably during a single event (Bauluz et al, 2002;Bauluz, 2007). The effect of fluid composition and the fluid/rock ratio on clay formation in hydrothermal environments is more significant (e.g., Whitney, 1990;Buatier et al, 1992;Harvey and Browne, 1992;Inoue andKitagawa, 1994, Inoue, 1995), and the crystallinity of clay minerals is largely controlled by fluid temperature (Browne and Ellis, 1970;Duba and William-Jones, 1983;Hedenquist and Browne, 1989;Ji and Browne, 2000;Zhangdong et al, 2001Zhangdong et al, , 2002Fukuchi et al, 2014). If clay minerals precipitated in equilibrium with the fluid (without any kinetic isotope fractionation) the H-and O-isotope composition of the clays can be used to infer the fluid isotope composition (if the fluid temperature is known) or temperature (if the fluid isotopic composition is known).…”

Post‐impact alteration of surficial suevites in Ries crater, Germany: Hydrothermal modification or weathering processes?

“…Hydrothermal alteration in active endogenic hydrothermal systems is typically characterized by a zonal distribution of alteration and directional distribution of altered minerals that is principally related to mass transfer between minerals and hydrothermal solutions as temperature decreases when the hydrothermal solutions pass through rock (Helgeson 1979). The distance between the high-temperature and lowtemperature zones is a factor of the vertical thermal gradient at a given place (Inoue 1995;Meunier 2005). Importantly, as the number of variables in a hydrothermal system increases, a greater variety of clay minerals can be expected to form under different hydrothermal environments (Inoue 1995).…”

“…The distance between the high-temperature and lowtemperature zones is a factor of the vertical thermal gradient at a given place (Inoue 1995;Meunier 2005). Importantly, as the number of variables in a hydrothermal system increases, a greater variety of clay minerals can be expected to form under different hydrothermal environments (Inoue 1995). The same spatial structure and specific alteration gradients of the hydrothermal alteration are described for IHT systems.…”

Outlining the thermal posdepositional evolution of the Ordovician successions of northwestern Argentina by clay mineral analysis, chlorite geothermometry and Kübler index.

“…The common occurrence of kaolinite in the slates and the metavolcanic rocks of Sierra de CochinocaEscaya studied, coupled with the substitution of chlorite by interstratified lower-temperature phases in most of these rocks also indicate hydrothermal fluids with high H + /cations ratios, producing acid type alteration, at temperatures of between 100 and ~300 °C (Utada, 1980;Inoue, 1995). Up to now, the only evidences of hydrothermal activity connected with the Ordovician arc mentioned in the literature was the occurrence of several mineralized quartz veins hosted in Ordovician beds in the Sierra de Santa Victoria and Sierra de Cochinoca-Escaya (Craig et al, 1995;Coira et al, 2001).…”