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Ar-40/ar-39 ages for maskelynites and k-rich melt from olivine-rich lithology in (kanagawa) zagami
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | Nyquist, L. E. Delaney, J. S. Misawa, K. Shih, C.-Y. Lindsay, F. Swisher II, C. C. Herzog, G. F. Park, J. Turrin, B. Niihara, T. |
| Copyright Year | 2013 |
| Description | We report Ar/Ar release patterns for small maskelynite grains and samples of a K-rich phase separated from the basaltic shergottite Zagami. The purpose of the work is to investigate the well-known discrepancy between published Ar/Ar ages of Zagami, >200 Ma, and its age of approx. 170 Ma as determined by other methods [1-6]. Niihara et al. [7] divide less abundant darker material present in Zagami into an olivine-rich lithology (ORL), from which most of our samples came, and a pyroxene-rich one (Dark Mottled-Lithology: DML) [8, 9]. ORL consists of vermicular fayalitic olivine, coarse-grained pyroxene, maskelynite, and a glassy phase exceptionally rich in K (up to 8.5 wt%), Al, and Si, but poor in Fe and Mg. The elemental composition suggests a late-stage melt, i.e., residual material that solidified late in a fractional crystallization sequence. Below we refer to it as "K-rich melt." The K-rich melt contains laths of captured olivine, Ca-rich pyroxene, plagioclase, and opaques. It seemed to offer an especially promising target for Ar-40/Ar-39 dating. |
| File Size | 588176 |
| Page Count | 2 |
| File Format | |
| Alternate Webpage(s) | http://archive.org/details/NASA_NTRS_Archive_20130011089 |
| Archival Resource Key | ark:/13960/t9x113f89 |
| Language | English |
| Publisher Date | 2013-03-18 |
| Access Restriction | Open |
| Subject Keyword | Geophysics Olivine Pyroxenes Shergottites Lithology Crystallization Basalt Plagioclase Chemical Composition Achondrites Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science |
| Content Type | Text |
| Resource Type | Article |
