Mineralogical study of outcrop and soil samples from the central portion of the Gladesville norite suggests that quartz has been synthesized during soil genesis. Quartz does not occur in outcrop samples, but is the most abundant mineral constituent in soil samples collected from the B-horizon. In a soil profile sample it occurs at all depths but is sharply concentrated in surface horizons. The overall abundance and distribution of quartz in the soil samples can not be adequately explained by surface erosional processes. Adsorption of silica by amorphous Fe-Mn oxides and impeded drainage conditions have been shown by other studies to be important in producing environmental conditions favorable for inorganic synthesis of quartz under earth-surface conditions. Both controls are well-developed in the area studied. It is believed that secondary quartz, precipitated during weathering and soil genesis, occurs in soil overlying the norite.

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