Kayla, Jane, and Bradley are on a quest to find gold. They’ve gathered a map of gold deposits and are exploring the surrounding area. Their goal is to find the gold, which they believe is hidden deep underground. However, they’ve encountered obstacles along the way. With a map in hand, they must decide which gold deposits to explore next. After all, how does a map of gold find its locations?
Geologic occurrences
There are various types of geologic occurrences of gold, but in general, it is found in low concentrations in igneous rocks. Throughout Earth’s crust, the gold is dispersed as mineral flakes. Lode deposits form when heated fluids flow through gold-bearing rocks, picking up gold and depositing it in new locations. These deposit types are distinguished by chemical and physical properties of the fluids. Heavy gold tends to settle in lakes, streambeds, and sea floors.
When gold is dissolved in water, it precipitates from the rock surface. In other cases, gold is carried up from great depths by aqueous solutions. Some gold deposits have been found near large masses of granitic rock, which represents solidified magma. The main characteristics of these deposits are the presence of gold and traces of copper. Gold deposits in Illinois are also found in the North American continent.
Locations of gold deposits
Several states in the western United States have gold deposits. The Geological Survey, for example, produces reports on the districts with the greatest concentrations of gold. State liaison offices for the Bureau of Mines can also provide information. In some places, there are small rivers and saprolite deposits that contain gold. These deposits are called placers and can be mined by a variety of methods. However, they tend to be less attractive to prospectors because of the lack of a reliable water source.
Gold occurrences in small-scale maps tend to be near a young intrusive. In these areas, the most likely location for a large-scale gold deposit is adjacent to such an intrusive. However, the extent of this correlation is unproven. Using the Studentized C curve as the cutoff, only 8% of large-scale gold deposits are located within a few kilometers. The Studentized C curve peaks at 750 meters.
Predictive maps
A predictive gold map is a visualization of gold potential by combining the spatial associations of indicative geologic features. It is based on a statistical procedure and is applied to subsets of known mineral occurrences. The best predictive map defines 27% of the area as a gold-mining zone and 6.2% as highly favourable. It is based on knowledge-based methods that use fuzzy logic and a distribution of known mineral occurrences to estimate the probability of gold mineralization.
The spatial coherence of the deposits is essential for predictive gold maps. In the case of orogenic gold, the best predictive orogenic gold prospectivity map was created by combining an updated lithological map with spatially coherent orogenic gold occurrences. It was able to correctly predict the presence of gold in 20% of the GGB with a goodness-of-fit of 89%. This approach uses spatial evidence to estimate gold-mining potential.
Prospecting for gold
If you are interested in prospecting for gold, then you should have a good understanding of geology. Gold deposits may not be visible in the rock and require laboratory analyses. Normally, samples of three to five pounds of representative mineralized rock are sent to an assay office or commercial analytical laboratory. Before starting your search, however, you should understand the general direction of the geology of the area you are prospecting. Generally, the gold-bearing area will have a 90-degree trend to the prevailing geology.
The first thing to know about the gold-bearing area is whether or not it is legal to mine. There are many areas where you can prospect legally on public land. However, you should find out whether or not your area is on private or public land. If you’re planning to do some mining, you should first learn more about the laws and regulations governing gold-mining. A map is an essential tool to find the best place to start your gold-bearing activities.