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[1] [2] Metamorphic minerals are unstable upon changing P-T conditions. [1] [3] The original minerals are commonly destroyed during solid state metamorphism and react to grow into new minerals that are relatively stable. [1] [3] Water is generally involved in the reaction, either from the surroundings or generated by the reaction itself. [3]
Metamorphic rocks are formed when existing rock is transformed physically or chemically at elevated temperature, without actually melting to any great degree. The importance of heating in the formation of metamorphic rock was first noted by the pioneering Scottish naturalist, James Hutton, who is often described as the father of modern geology ...
The oldest dated rocks formed on Earth, as an aggregate of minerals that have not been subsequently broken down by erosion or melted, are more than 4 billion years old, formed during the Hadean Eon of Earth's geological history, and mark the start of the Archean Eon, which is defined to start with the formation of the oldest intact rocks on Earth.
This scheme is used to date old igneous and metamorphic rocks, and has also been used to date lunar samples. Closure temperatures are so high that they are not a concern. Rubidium-strontium dating is not as precise as the uranium–lead method, with errors of 30 to 50 million years for a 3-billion-year-old sample.
[1] Monazite geochronology is a dating technique to study geological history using the mineral monazite. It is a powerful tool in studying the complex history of metamorphic rocks particularly, as well as igneous, sedimentary and hydrothermal rocks. [2] [3] The dating uses the radioactive processes in monazite as a clock.
The Tetons and other north-central ranges contain folded and faulted rocks of Paleozoic and Mesozoic age draped above cores of Proterozoic and Archean igneous and metamorphic rocks ranging in age from 1.2 billion (e.g., Tetons) to more than 3.3 billion years (Beartooth Mountains). [16]
A shield is a large area of exposed Precambrian crystalline igneous and high-grade metamorphic rocks that form tectonically stable areas. [1] These rocks are older than 570 million years and sometimes date back to around 2 to 3.5 billion years.
Sometime around 2.5 billion years ago, blobs of magma intruded into the older rock, forming plutons of granitic rock. [3] Extensive exposures of this rock are found in the central part of the range. About 1.3 to 1.4 billion years ago in Late Precambrian, 5-to-200-foot (1.5 to 61.0 m) thick black diabase dikes intruded as well, forming the ...