Wall-Rock Alteration

The veins are composed mostly of quartz and a small amount of sulfide minerals (pyrite, pyrrhotite, arsenopyrite, chalcopyrite, sphalerite, and galena), carbonate minerals (calcite, dolomite) and gold, and include breccias of the host rocks with carbonaceous matters. Layering by carbonaceous matters has been occasionally observed in the veins. Banding structure, wall rock alteration and an evidence of boiling of fluids that are commonly observed in epithermal veins have not been usually found. 

Doi, S. (1972) Wall rock alteration at the Akeshi and Iwato mines with special reference to the physicochemical environment of its formation. Unpub. Masters Thesis, U. Tokyo. 

Ibaraki, K. and Suzuki, R, (1990) Wall rock alteration in the Hishikari gold mine, Kagoshima Prefecture, Japan. Mining Geology, 40, 97-106 (in Japanese with English abst.). 

Matsueda, H., Yui, S. and Kurosawa, K. (1992) Hydrothermal ore deposits and wall rock alteration in southwestern Hokkaido (A04). In Urabe, T. and Aoki, M. (eds.). Mineral Deposits of Japan and the Philippines. 29th IGG Field Trip Guide Book vol. 6. Tokyo Soc. Resource Geol., pp. 17-60. 

Meyer, C. and Hemley, J.J. (1967) Wall rock alteration. In Barnes, H.L., (ed.). Geochemistry of Hydrothermal Ore Deposits, Holt Rinehart Winston, pp. 166-235. 

Sawai, O. (1984) Wall rock alteration around the Motoyama deposits, Toyoha mine, Hokkaido, Japan. Mining Geology, 34, 173-186 (in Japanese). 

Sawai, O. (1999) Wall rock alteration of the Toyoha polymetallic vein-type deposits,. southwestern Hokkaido, Japan. Resource Geology Special Issue, 20, 99-112. 

Takahashi, H. (1988) Wall-rock alteration and ore-formation model of Hosokura Pb-Zn ore deposits, Japan. Mining Geology, 38, 335-346 (in Japanese). 

Scott, K.M. (1986) Sulphide geochemistry and wall rock alteration as a guide to mineralization, Mammoth Area, NW Queensland, Australia. Journal of Geochemical Exploration, 25, 283-308. 

Nickel, E. H. (1954) The distribution of iron, manganese, nickel and cobalt between coexisting pyrite and biotite in wall-rock alteration. Amer. Mineral., 39,494-503. 

The rock quality designations (RQD the total length of solid core pieces that have individual lengths more than 10 cm, measured axially between discontinuities) of both the moderately and the intensely fractured zones are nearly 0%. Each fracture and fractured zone has been characterized to determine its length, width and continuity and the nature of the filhng minerals. These different zones have different types of wall rock alteration. The distributions of fractured zones are shown in Fig. 4. 

In contrast to the hardly investigated lateral zonation around Japanese epithermal vein-type deposits, a few examples of vertical zonation are known. Potassic alteration grades upwards into intermediate argillic alteration in the wall rocks for the Toyoha (Okabe and Bamba, 1976), Ohe (Tsukada and Uno, 1980), Chitose (Hasegawa et al., 1981) and Kushikino (Imai, 1986). 

Shikazono, N., Hoshino, M., Utada, M., and Ueda, A. (1998) Hydrothermal carbonates in altered wall rocks at the Uwamuki Kuroko deposits, Japan. Mineralium Deposita, 33, 346-358. 

Shirozu, H. (1974) Clay minerals in altered wall rocks of the Kuroko-type deposits. In Ishihara, S. (ed.). Geology of Kuroko Deposits, Mining Geology Special Issue, 6, 303-310. 

We further specify equilibrium with kaolinite [Al2Si205(0H)4], which occurs in at least some of the veins as well as in the altered wall rock. Since we know the fluid s potassium content (Table 22.1), assuming equilibrium with kaolinite fixes pH according to the reaction,... 

The Silver Bell Mine area consists of dipping units that are composed of dacite porphyry, alaskite and monazite. The rock ages span the Paleozoic, Mesozoic and Cenozoic periods. The Paleozoic wall rocks consist of quartzite, siltstone and altered limestone. The carbonate rocks are exposed along the contact between the host rock and intrusions, and host the... 

The lithogeochemistry of wall rocks in the Hollinger-Mcintyre-Coniaurum (HMC) deposit has not been fully explored. The objective of this study was to characterize the lithogeochemical alteration of the wall rocks and the stable isotope geochemistry of the veins in order to (1) test if the HMC deposit is zoned chemically (2) determine how many mineralizing events were involved in forming the HMC deposit and (3) identify fluid pathways involved in formation of the HMC gold deposit. 

In an exploration area in northern Peru, igneous rocks cover an area of several square km within a metamorphosed series of quartzites and limestones. The younger sequence consists of ignimbrites, tuffs and tuffites of approximately 1000 m thickness. The metamorphism produced skams, which are connected with the ore body. A porphyry Cu deposit occurs in the metamorphosed rocks and is characterised by intense hydrothermal alteration (quartz-kaolinite-sericite) which makes determination and classification of magmatic and sedimentary rocks at the surface very difficult. A zone of propylitic alteration can locally be followed up to 500 m into the andesitic-dioritic wall rocks. 

Obtaining meaningful Ar isotope analyses on basalts is analytically challenging, because contamination by atmospheric components is notorious. Potential sources of this contamination include seawater, altered wall rock, or air itself. Basalt glasses may show complicated variations within an individual glassy rim, with lower in both the... 

In fact, all three processes are likely to have contributed to affect the isotopic compositions of strontium and neodymium and the concentrations of the respective parent and daughter elements. Although the chemical composition of the basalt magma was undoubtedly changed both by simultaneous fractional crystallization and assimilation of wall rock, the isotopic composition of strontium and neodymium is altered only by the assimilation of a contaminant and not by fractional crystallization. 

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