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GEL 20 - Quiz 3
Terms in this set (20)
The majority go gold mines in the Sierra Nevada occur where?
In the foothills which marks the location of accreted terranes of the Western Metamorphic Belt
As the superheated waters come in contact with the cold ocean water, the elements crystallize as part of chimneys called what?
When these fluids could travel no further along cracks or fault planes, the dissolved silica precipitated out of what?
Where and what is the Mother Lode?
The Mother Lode gold belt of the Sierra foothills is a 1.5 km wide zone of gold-bearing quartz veins and mineralized rock that runs for 195 km along the Western Metamorphic Belt. Located along a major fault zone separating terranes.
There are three types of gold deposits in the Sierran foothills what are they?
1) lode deposits, exploited by hard rock mining
2) placer deposits in modern streams and rivers
3) placer deposits in ancient river sediments
The Mother Lode is similar to what type of gold deposits?
T/F: Where the Lode Deposits the original source of the most of the gold mined from the Sierra.
required cutting deep shafts in solid rock to extract the ore.
Requires picks, shovels, drills, dynamite and other heavy equipment to break out the quartz, then chemically separate it from any associated gold
Where is Placer gold found?
In modern rivers and streams
The gold-bearing quartz veins had been exposed to erosion for millions of years before the miners found them. The erosional debris from these veins had washed off into modern streams and rivers as part of the sediment along the bed, forming what?
Due to gold being durable and resistant to weathering what is the effect of this?
it moves along the beds of streams with the rest of the sediment until it accumulates along sand bars
Where are Auriferous gravels located?
In placer gold in ancient river deposits
Rivers were choked with coarse gravelly sediment, which caused the river to spread out laterally into a sinuous network of interweaving smaller streams, called what?
The 49ners mined these ancient placer deposits by diverting streams downhill into pipes that fed powerful water cannons that blast away at the hillsides. The forcibly eroded sediment was diverted into sluices where the gold was washed out.
This type of mining was called what?
What was the environmental destruction of hydraulic mining?
- natural stream courses were changed to divert water into the cannons.
- enormous volumes of sediment were flushed into the streams
- The choked channels forced the water out of its banks and flooding became common
- Coarse hydraulic sediment would wash out over farmland in the Central Valley during the frequent floods
Another environmental destructive aspect of gold mining in the Serra was the use of what?
The use of mercury in order to separate the gold from rest of the rock and sediment
What are alpine glaciers?
Thick masses of ice found in deep valleys or in upland hollows
rivers of ice that fill valleys between mountains
What are continental ice sheets?
large ice sheets like Greenland and Antarctica
The most recent glacier phase peaked around 20,000 years ago and it is called...
The Last Glacial Maximum
T/F: Continental ice sheets advanced and retreated >20 times over the past 2 m.y., with cold glacial phases alternating with warmer interglacial phases
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