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CARBONAT IZATION

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The Wenn: fault zone and many of ‘its subsidiary shears are marked by the development of quartz-carbonate- chlorite-mariposite rocks. Drag-folded strata on both sides of the main zone indicate much movement in the early stages of faulting, resulting, apparently, in intense shearing of the rocks involved, and in the alteration of andesites to chlorite schists, argillites to graphitic schists, and limestones to carbonate-sericijte schists. These shear zones acted as channelways for later carbonated solutions that attacked the sheared rocks and replaced them with a varying mixture of ankerite, secondary quartz, chlorite, and mariposite. These carbonatized rocks formed relatively rigid bands along -which later movements developed open fractures rather than

closed shears. Subsequent mineralizing solutions traversing the fractures filled them with vein quartz and resulted in further carbonatization, silicification, and pyritization of the wall-rocks of the carbonatized zone. Two periods of quartz- vein deposition may be recognized, the later one carrying the gold that is believed to have been: the source of the Manson River placer deposits. Post-mineral movements along the _carbonatized zone has resulted in nearly horizontal offsets of the quartz veins amounting to only a few feet. Carbonatization did not extend far from the main zone into subsidiary fractures most of which exhibit little alteration and still preserve the evidence of earlier shearing

Those shear zones in “close proximity to igneous intrusions have been altered to tale-chloritc-carbonate schists in which-the effect of carbonatizgation -has been slight.

ECONOMIC GEOLOGY (Pinu EO GMOnTOn

Placer gold wags discovered on Germansen River in 1870 and | on. Manson River in 1871. Since then some gold has becn produced each year, the total value probably exceeding $1,500,000. The cost of extraction has probably exceeded the value Of all the gold recovercd. Relatively large: scale : operations were carried out between 1933 and the present.

The arca has witnessed comparatively little lode prospecting. Souoree showings have, however, been staked, and a few others were discovered by the ‘writers! party while — engaged in vee work, but as yet the limited amount of work on these has not proved a commercial orebody.

Placer Deposits

The placer deposits of the area have been found both in present stream gravels and in stream channels underlying glacial drift. Recent gravels are usually shallow and easily worked by individual miners, and undoubtedly supplied much of the gold extracted before 1900. The old buried channels are capped by as much as 80 feet of glacial drift, and may be mined successfully only on a relatively large scale and by hydraulick- ing, steam-shovelling, drag~line and ground-sluicing methods. The main deposits on the properties of Huffman Placers, Germansen Mines, Limited, Consolidated Mining and Snelting Company, Limited, and Lost Creek Placer Gold, Limited, are in