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Significance of elevated k/rb ratios in lower crustal rocks
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | Frost, B. Ronald Frost, Carol D. |
| Copyright Year | 1988 |
| Description | The granulite uncertainty principle, which states that it is difficult or impossible to determine with certainty the maximum geopressure and geotemperature that a granulite has experienced, is addressed. Also, geochemical fingerprinting cannot always be used reliably in the nebulous region that is transitional between metamorphic and igneous environments. Ion exchange thermometers are typically useful to approximately 800 C in slowly cooled plutonic rocks unless one uses a reintegration technique on unmixed minerals, or unless a metastable mineral assemblage can be observed. It is argued that in most granulites, fossil temperatures are typically obliterated by reequilibration and/or deformation during slow cooling. Granulite metamorphism may be further complicated by the common association with igneous activity. The previously-used geochemical indicators such as high K/Rb ratios and LIL depletion may not be strictly the result of granulite facies metamorphic depletion, but also may result from igneous processes, which depend on bulk and mineral compositions and on the mineralogy of the protolith. Detailed geologic mapping will be the ultimate arbitrator of whether a given geochemical signature is the result of igneous or metamorphic processes. |
| File Size | 191736 |
| Page Count | 3 |
| File Format | |
| Alternate Webpage(s) | http://archive.org/details/NASA_NTRS_Archive_19890012834 |
| Archival Resource Key | ark:/13960/t3nw4c378 |
| Language | English |
| Publisher Date | 1988-01-01 |
| Access Restriction | Open |
| Subject Keyword | Geophysics Deformation Cooling Geotemperature Mineralogy Geochemistry Granite Fossils Ion Exchanging Geological Surveys Depletion Earth Crust Metastable State Geopressure Metamorphism Geology Signatures Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science |
| Content Type | Text |
| Resource Type | Article |
