EXPM:HRTFF - Post by User
Comment by
cheerio7on Mar 22, 2017 6:23pm
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Post# 26017045
RE:RE:Sediments and Volcanic suite of rocks significance...
RE:RE:Sediments and Volcanic suite of rocks significance...Maybe this will help...
"The deposit is of Archean age and occurs at the contact of felsic metavolcanics and pelitic metasediments. The ore minerals were formed from hydrothermal fluids that may in part be related to the shear zone." So taking out the geo-speak the Hemlo deposit was found where the sedimentary rocks and the volcanic rocks meet. Hence, when SR talks about this area or package of rocks at the southern limit of the Dayo Lake he is speaking to this theory of ore deposit emplacement and its corresponding very prospective potential. As Bell puts it...mineralizing fluids from fissures or cracks in the sides of the ancient volcano flowed up and deposited the gold (or precipitated it) in beds which formed in proximity to these vents (fissures/cracks). This basic type of mineralizing mechanism is responsible for a great many of the world's largest (by metal content) ore deposits. VMS and SEDEX deposits among others have this mineralizing engine in common. Thus, the volcanics, layers of newly formed rock derived from the volcano or better the sub reaches of the earth, formed a base for the beds of fissure fluid emplaced mineralization that were later blanketed by a sedimentary formation of rocks, formed by the erosion and persistent breakdown of the area by mother nature and consolidated by pressure and time. Since this all occurred roughly 2.7 billion years ago over a time period of many millions of years, the ground has been subject to much metamorphism (hence the *meta* in metavolcanics and metasediments) in a way whereby an assemblage of rocks may become flipped or twisted thereby resulting in them lying side by side instead of on top (the sediments) and below (the volcanics) of each other.
Best to all
C7