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U-pb zircon geochronology and evolution of some adirondack meta-igneous rocks
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | McLelland, J. M. |
| Copyright Year | 1988 |
| Description | An update was presented of the recent U-Pb isotope geochronology and models for evolution of some of the meta-igneous rocks of the Adirondacks, New York. Uranium-lead zircon data from charnockites and mangerites and on baddeleyite from anorthosite suggest that the emplacement of these rocks into a stable crust took place in the range 1160 to 1130 Ma. Granulite facies metamorphism was approximately 1050 Ma as indicated by metamorphic zircon and sphene ages of the anorthosite and by development of magmatitic alaskitic gneiss. The concentric isotherms that are observed in this area are due to later doming. However, an older contact metamorphic aureole associated with anorthosite intrusion is observed where wollastonite develops in metacarbonates. Zenoliths found in the anorthosite indicate a metamorphic event prior to anorthosite emplacement. The most probable mechanism for anorthosite genesis is thought to be ponding of gabbroic magmas at the Moho. The emplacement of the anorogenic anorthosite-mangerite-charnockite suite was apparently bracketed by compressional orogenies. |
| File Size | 163533 |
| Page Count | 3 |
| File Format | |
| Alternate Webpage(s) | http://archive.org/details/NASA_NTRS_Archive_19890012851 |
| Archival Resource Key | ark:/13960/t74v1h64s |
| Language | English |
| Publisher Date | 1988-01-01 |
| Access Restriction | Open |
| Subject Keyword | Geophysics Intrusion Geochronology Minerals Magma Gneiss Adirondack Mountains Ny Zirconium Earth Crust Isotherms Rocks Metamorphism Geology Anorthosite Isotopes Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science |
| Content Type | Text |
| Resource Type | Article |
