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Gold/Mining/Energy : Golden Eagle Int. (MYNG) -- Ignore unavailable to you. Want to Upgrade?

To: Mike Gold who wrote (11516)	7/29/1998 7:28:00 PM
From: jbIII	Respond to of 34075

definition; minerals.net jb3

To: Mike Gold who wrote (11516)	7/29/1998 9:09:00 PM
From: E. Charters	Read Replies (1) \| Respond to of 34075

There is epi, meso and hypothermal. They refer to the temperature of the vein and and its supposed distance from the heat source. Texts are divided on the best type to find. On one hand they say that distal epithermal veins are conducive to the largest deposits. But the average epithermal gold deposit is about 1 million tons. The Nevada Goldstrike deposit precipitated from downwardly circulating waters rather than from below and that explains its quick drop in grade at depth in part. Most gold deposits of primary origin are related in some manner to nearby volcanism and a felsic mass that provides the heat to keep hydrothermal solutions of silicic and sulfuric acid emanating towards the dilation-precipitation zones. It is the precipitative environment that dictates the nature of a deposit. There is no guarantee that if there is a vein that all metals precipitated from it equally at every point. The associated minerals, chiefly micas tell the geologist the temperature regime and thus the likely precipitation environment of the Gold. It is instructive to note that silica has the same melting temperature as gold, so its association is not accidental. The formation of gold deposits is from hot water solution however, not at melting temperatures of quartz for the most part. Sedimentary deposits are the result of many such alpine veins originally hydrothermally formed at high temperature breaking down and in a process of eluvial and mass wasting depletion having their lighter components washed away in those high, high energy environments. Placer deposits take lower grade veins and wash them to higher grade gravel beds. It is not deposition but removal that forms the placer, fossil or unconsolidated. If a sandstone of a fine nature is promoted as a possible placer host I would doubt it strongly. It either must be a breccia host or its grain size on the average must approach lapilli (2.5.to 4 inch diameter rocks) and there should be association with iron and other heavy minerals.. perhaps uranium and platinum. EC<:-}