A friend recommended a video showing impressive large quartz crystals. They were found in the Coleman Quartz Mine in Arksansas, USA. As far as I know these clear quartzes were formed by hydrothermal processes and are bound to large fault zones within Ordivician sandstones. (more…)
Archive for the ‘Geo-Topics’ Category
Gold-bearing quartz veins related to the orogenic gold type are typically ribboned as known from my research area northern California. The ribbons there are formed by vein-parallel shear planes, dividing the quartz in decimeter to micrometer thick bands. Ore-bearing fluids intruded the shear planes several times. This multi-stage mineralization is verified by microscopic investigation of gold ore. In most cases gold and galena are the last species deposited in the veins. The veins occur dominantly at intensely sheared lithological contacts.
A result of these observations is that the deposits developed in an active tectonic environment with multiple stages of fluctuating fluid influx in depths characterized by brittle deformation.
To improve my own understanding of fluid migration processes in hydrothermal systems I will try to summarize some general thoughts I worked off for myself from Cox et al. (2001) and, in part, from Yardley (1983). This is certainly not a complete overview of the topic. So donâ€™t hesitate to post critical questions, remarks or further arguments and ideas. (more…)
It has been a fierce competition with high-quality mining photographs. My photos did not win, but there is a chance in the people’s choice category. The online-voting opens today. I would like to invite you to vote for your favorite mining photograph. Please spread this information. Thanks!
Addition: I have been too hasty… my photographs were not chosen for online voting, but don’t hessitate to vote for the other fantastic submissions!
Thank you for voting about 3 out of 14 mining photographs I will submit to the Snowden photo Ccompetition. The decision has been ambiguous. Depending on the evaluation procedure three groups of your favorites can be found:
- the first three photographs in the category “1st place”: photos 3, 8, 4
- the first place in each category (“1st place” to “3rd place”): photos 3, 12, 14
- the three photographs with the highest total number of votes: photos 8, 14, 4 (more…)
In the last two years I participated in the Snowden Photo Competition. This year the submission deadline ends June 30th. In the following you’ll find some of my favorite mining photographs out of which 3 photographs have to be chosen for this year’s competition. It would be great to get some of your opinions. What are YOUR favorite 3 out of the 14 photographs presented below? VOTE HERE…
I will randomly choose one person out of all voting participants, who will get the best voted photograph as 20×30 cm large print via mail. Thank you!
Voting will end Saturday, June 26th, 2010.
The son of Mother Lode? State and perspectives of the gold deposit research in the French Gulchâ€“Deadwood district, Klamath Mountains, USAWednesday, June 16th, 2010
By Lutz Geißler & Thomas Seifert
Mother Lode gold has been of scientific interest since the famous Californian gold rush began in 1848 in the Sierra Nevada foothills. Mining these clusters of low-sulfide gold-quartz veins bound to a major NW-SE trending fault zone in a tectonically active metamorphic complex yielded approx. 86 million ounces of gold (including placer deposits; Böhlke, 1999). Besides the strong impact on the economical development of the western United States of America, Mother Lode has been and is still a significant key for defining and characterizing the globally important â€śorogenic goldâ€ť deposit type. In contrast to this geologically well known gold belt, most of the gold deposits of the northerly located Klamath Mountains were never investigated with modern geoscientific methods. Researching their genesis in comparison to the Mother Lode deposits may be essential (1) for an improved geotectonic model of northern California, (2) for an enhanced understanding of orogenic gold deposits, and (3) for characterizing new exploration targets. (more…)