Thor Deposit
Host Rocks
Host Rocks - Broadview and Sharon Creek Formations
The host rocks at Thor are very important for understanding the structural setting of the deposit. Taranis geologists have spent considerable time mapping these rocks and the structural features they preserve.
What Do the Host Rocks Look Like?
The host rocks at Thor can be recognized by their banded nature. This banding is largely due to the layering within the sedimentary rocks. Banding in sedimentary rocks forms when the environment of deposition changes through time, producing visible layers that differ in color, grain size, mineral content, or chemistry. These bands—often called bedding or stratification—are one of the most fundamental signatures of sedimentary processes. Alteration modifies the original sedimentary fabric. These changes can be subtle or dramatic depending on fluid chemistry, temperature, and rock composition. The changes include color changes, formation of new minerals, veining, and textural changes.
In districts like the Silver Cup area, alteration in sedimentary rocks can reveal:
In districts like the Silver Cup area, alteration in sedimentary rocks can reveal:
The host rocks commonly exhibit carbonaceous alteration, giving them a distinctive black color. Taranis has studied this form of alteration in great detail at Thor.
In thin section, the host rocks are tightly folded, having been compressed. This assymetric style of folding is characteristic of the Silver Cup Mining District
What are Host Rocks?
Other Information About Host Rocks
Host rocks are the rocks that physically surround, enclose, or contain an ore deposit, and they matter because they control how the deposit formed, how it’s altered, and even how it can be mined. At Thor, these rocks are metamorphosed metasedimentary rocks (greywackes and pelites), and minor volcaniclastic rocks. These rocks are lower Paleozoic in age and were deposited on the west side of North America in a sedimentary basin. These rocks have been deformed by folding and faulting, and in some cases thermal metamorphism (see lamprophyre alteration).
Perhaps the most important feature that can be described about host rocks is the tight folding that can be found. These folds generally trend northwest along the Silver Cup Anticline, and they are commonly sheared along the limbs. All of the folding at Thor plunges shallowly (about 35 degrees) to the northwest and this allows the fold to be identified in the subsurface.
The host rocks also include a significant level of organic hydrocarbon, and this is due to the presence of organic matter in the sedimentary rocks. Despite the presence of organic matter, a fossil has never been seen at Thor!
The host rocks also include a significant level of organic hydrocarbon, and this is due to the presence of organic matter in the sedimentary rocks. Despite the presence of organic matter, a fossil has never been seen at Thor!