Post by 1dave on Feb 26, 2014 10:37:03 GMT -5
An extension of Geology for Rockhounds.
Why rob banks?
Because that is where the MONEY is!
Why Hound Mineral Belts?
Why are the Large Mines located where they are?
geology.utah.gov/online/ofr/ofr-515.pdf
For the past 4.5 billion years the earth has been sorting itself; the lighter stuff (felsic - feldspars quartz) accumulating at the surface, the heavy stuff sinking towards the core. A lot of heavy minerals were anciently trapped in the basaltic sea floor crust.
Cratons (continents) are rafts of low density felsic rock, commonly composed of basalt, andesite, or granite, which has been extracted and accumulated at the surface.
Cratons grow as plate motions move them about the surface of the earth and they crunch into other crustal plates. This process, named Plate tectonics, explains the occurrence and location of nearly all earthquakes and most volcanoes. It also explains origin and location of mountain belts and some mineral resources
The North American Craton is currently adding land along its western margin where it is colliding with the Pacific plate along a long linear zone of faulting called a subduction zone. The light stuff sticks to the existing land, the heavy stuff is plowed under to be remelted at the mantle. Most of what is added are small cratons formed as volcanic arcs associated with the subduction process. It is common for sections of oceanic crust, often sediments but usually basalt, to get caught up in the accretion process and become wedged in between other incoming sections.
Greenstone is a dark, tough, altered basaltic rock that was once solid deep-sea lava, but has now modified to metamorphic greenschist or greenstone. As the dark non-felsic minerals such as olivine and peridotite of the ocean crust were exposed to high pressure and warm fluids, they were metamorphosed, then further modified by surface weathering processes into dark green minerals; serpentine, epidote, actinolite, chlorite, jade and jadeite. The results are green stones, and these additions of mafic crusts are called “greenstone belts.”
Read more at:
Greenstones
Greenstone From stop 31 of the California subduction tour
Photo (c) 2006 Andrew Alden, licensed to About.com (fair use policy)
Greenstone belts vary dramatically in size, ranging from as little as several dozen to several thousand kilometers in length. They are extremely common, and are found on almost every continent. Because they have survived many cycles of tectonics, their stratigraphy is complex, containing a great number of individual rock units.
Generally speaking, greenstone belts are composed of volcanic rocks that also have small amounts of sedimentary rocks interconnected within the various volcanic rocks. They horde economical deposits of many minerals including gold, silver, copper, and zinc. While greenstone belts host a variety of minerals, gold is most commonly found along the edges of these belts. Gold-bearing conglomerates are commonly associated with greenstone belts. Gold is found in Achaean age greenstone belts in Alaska, Australia, California, both coasts of Canada, southern Africa, etc. but, who cares?
Greenstone formation has happened many times in the past as cratons developed into the world we now inhabit, so greenstone belts exist inside most of the western states of the U.S. They, along with earthquake zones, are weak places in the crust that allow hot fluids and gases to flow through and accumulate many unusual minerals. Thus the term “mineral belts.”
In Utah, along the Wah-Wah-Tusher Mineral Belt Fluorine gas was exhaled, creating Fluorite and Topaz crystals. Beryl crystals were also formed along with silver and gold deposits.
along the Iron Axis Fluorine and Chlorine gas combined with other elements to form Apatite crystals before the molten iron was pressed in.
We have Chlorine Belts, Fluorine Belts, Carbonate Belts, Sulfate Belts, Oxide Belts, and Rare Earth Belts.
The mineral belts are where interesting things happened.
General Observations:
1. Western States Mineral Belts follow inherited zones of weakness in Precambrian (Over 600 Million years old!)rocks that generally trend toward the northeast.
2. Major Intrusions and ore deposits tend to be widened at intersections of NE-trending belts with younger NW trending shear zones by emplacement of intrusions and localized ore-related hydrothermal activity.
3. Three major periods of mineralization have occurred about 32 million years apart:
65 mya - Late-Cretaceous-early Tertiary (major), time of the Chicxulub asteroid impact.
34 mya - Mid-Tertiary (major), time of the Popigai asteroid impact.
2.6 mya - Late-Tertiary (minor), time of the Kara-Kul asteroid impact/
Believe it or not, Alaska has mineral belts and wealth.
So does Nevada.
Idaho is something else! No wonder they call it the GEM STATE!
Colorado has a few worth mentioning:
Arizona has outstanding Mineral Belts!
But who cares about any of that crap?
Why rob banks?
Because that is where the MONEY is!
Why Hound Mineral Belts?
Why are the Large Mines located where they are?
geology.utah.gov/online/ofr/ofr-515.pdf
For the past 4.5 billion years the earth has been sorting itself; the lighter stuff (felsic - feldspars quartz) accumulating at the surface, the heavy stuff sinking towards the core. A lot of heavy minerals were anciently trapped in the basaltic sea floor crust.
Cratons (continents) are rafts of low density felsic rock, commonly composed of basalt, andesite, or granite, which has been extracted and accumulated at the surface.
Cratons grow as plate motions move them about the surface of the earth and they crunch into other crustal plates. This process, named Plate tectonics, explains the occurrence and location of nearly all earthquakes and most volcanoes. It also explains origin and location of mountain belts and some mineral resources
The North American Craton is currently adding land along its western margin where it is colliding with the Pacific plate along a long linear zone of faulting called a subduction zone. The light stuff sticks to the existing land, the heavy stuff is plowed under to be remelted at the mantle. Most of what is added are small cratons formed as volcanic arcs associated with the subduction process. It is common for sections of oceanic crust, often sediments but usually basalt, to get caught up in the accretion process and become wedged in between other incoming sections.
Greenstone is a dark, tough, altered basaltic rock that was once solid deep-sea lava, but has now modified to metamorphic greenschist or greenstone. As the dark non-felsic minerals such as olivine and peridotite of the ocean crust were exposed to high pressure and warm fluids, they were metamorphosed, then further modified by surface weathering processes into dark green minerals; serpentine, epidote, actinolite, chlorite, jade and jadeite. The results are green stones, and these additions of mafic crusts are called “greenstone belts.”
Read more at:
Greenstones
Greenstone From stop 31 of the California subduction tour
Photo (c) 2006 Andrew Alden, licensed to About.com (fair use policy)
Greenstone belts vary dramatically in size, ranging from as little as several dozen to several thousand kilometers in length. They are extremely common, and are found on almost every continent. Because they have survived many cycles of tectonics, their stratigraphy is complex, containing a great number of individual rock units.
Generally speaking, greenstone belts are composed of volcanic rocks that also have small amounts of sedimentary rocks interconnected within the various volcanic rocks. They horde economical deposits of many minerals including gold, silver, copper, and zinc. While greenstone belts host a variety of minerals, gold is most commonly found along the edges of these belts. Gold-bearing conglomerates are commonly associated with greenstone belts. Gold is found in Achaean age greenstone belts in Alaska, Australia, California, both coasts of Canada, southern Africa, etc. but, who cares?
Greenstone formation has happened many times in the past as cratons developed into the world we now inhabit, so greenstone belts exist inside most of the western states of the U.S. They, along with earthquake zones, are weak places in the crust that allow hot fluids and gases to flow through and accumulate many unusual minerals. Thus the term “mineral belts.”
In Utah, along the Wah-Wah-Tusher Mineral Belt Fluorine gas was exhaled, creating Fluorite and Topaz crystals. Beryl crystals were also formed along with silver and gold deposits.
along the Iron Axis Fluorine and Chlorine gas combined with other elements to form Apatite crystals before the molten iron was pressed in.
We have Chlorine Belts, Fluorine Belts, Carbonate Belts, Sulfate Belts, Oxide Belts, and Rare Earth Belts.
The mineral belts are where interesting things happened.
General Observations:
1. Western States Mineral Belts follow inherited zones of weakness in Precambrian (Over 600 Million years old!)rocks that generally trend toward the northeast.
2. Major Intrusions and ore deposits tend to be widened at intersections of NE-trending belts with younger NW trending shear zones by emplacement of intrusions and localized ore-related hydrothermal activity.
3. Three major periods of mineralization have occurred about 32 million years apart:
65 mya - Late-Cretaceous-early Tertiary (major), time of the Chicxulub asteroid impact.
34 mya - Mid-Tertiary (major), time of the Popigai asteroid impact.
2.6 mya - Late-Tertiary (minor), time of the Kara-Kul asteroid impact/
Believe it or not, Alaska has mineral belts and wealth.
So does Nevada.
Idaho is something else! No wonder they call it the GEM STATE!
Colorado has a few worth mentioning:
Arizona has outstanding Mineral Belts!
But who cares about any of that crap?