Metamorphic Rocks
Taking the heat and pressure
Mining and Exploration
Geology Handbook
Pressure and Heat?
All rocks after they have been solidified one of two things (or different combinations) happen. Either they are broken down/eroded at the surface or they solidify deep in the earth. Either way, the immense pressures and temperatures within the earth will begin to change any rock, sedimentary, igneous or even other metamorphic into something new and maybe more exciting.
With depth in the earth increasing, both the temperature and pressure increases, to the point where eventually the rock melts and thereby creates new igneous rock. In that in between area however, the rocks go through a change, a metamorphosis if you please. The minerals within the rock will change as different Pressure and Temperatures (PT) allow for new minerals to form, and make other minerals break down.
The minerals that form are indicative of the pressure and temperature and when mapped out form a general metamorphic facies map. and looks something like this:
Happening Now
Whose exploring NW Ontario?
Exploration And permitting tablesThe table provided by MNDM shows the Plan or Permit number, the project name, the claim holder, all affected claims, the project location, any activities taking place and a start and end date for the activities. Activities...
Assuming the rock chemistry is constant!
The generalized Facies map above assumes that the rock/minerals present remain the same and are not contaminated from outside sources or have additional elements injected into the rocks. If this happens its a little bit more complicated.
For any given rock, only three things can change, the pressure, the temperature and its bulk chemistry (what elements are in the rock)
Chlorite, a common mica mineral which forms at low temperature/pressure. Its green…. Greenschist.
This is a peice of clorite schist.
Hornfels, created by contact metamorphism, where magama comes in contact with cooler sandstones and shale rocks. Typically near the surface by grasnitic intrusions.
Blueschist rocks, blue tinge priovided by glaucophane, a common blueish mineral.
Amphibolite rocks, formed deeper in the earth, coarser grained with abundant amphiboles and Plagioclase feldspar. Typically darker in colour with a salt/pepper appearance with more pepper, less salt.
