Framboidal textures

Framboidal textures which are common in Kuroko deposits are found in the deposits in less metamorphosed rocks (Watanabe et al., 1993). 

Type II mineralization is replacement type mineralization occurring in the fragmental tops of mafic flows, within the Sunnyside Formation near its lower contact with the Archibald Settlement Formation. Type II Veins and veinlets are commonly intricately banded with zones of early rhythmically-layered amorphous silica and later sulfide commonly displaying framboidal textures. 

Three textural types of pyrite occur in all samples examined 1) early framboids or irregular masses, 2) isolated euhedra, and 3) pyrites with massive cores and spongy or porous rims (Fig. 1). Types 2 and 3 occur in both shale and cross-cutting to bedding parallel veins, whereas type 1 occurs in shale only. 

Framboidal polycrystalline aggregation 157 Table 8.1 Terms used to describe textures of polycrystalline aggregates... 

The genesis of pyrite has claimed the attention of many workers. Pyrite has been synthesized chemically in the laboratory under a variety of temperatures and pressures (Berner, 1964a Roberts et al., 1969 Rickard, 1969). Pyrite framboids, so named because of their raspberry-like texture when viewed under a microscope, are found in clay sediments and silts, or as infillings of foram, diatom, or radiolarian tests. Biotic and abiotic mechanisms have been proposed for their formation (Schneiderhohn, 1923 Schou-ten, 1946 Love, 1965 Rickard, 1970). More recently, structures have been synthesized in the laboratory which resemble the pyrite framboids found in marine sediments (Berner, 1969 Farrand, 1970 Suna awa et al., 1971 Sweeney and Kaplan, 1973). On the basis of experiments with stable isotope... 

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