Crystallization history of lunar picritic basalt sample 12002: Phase-equilibria and cooling-rate studies

Research Article| May 01, 1976 Crystallization history of lunar picritic basalt sample 12002: Phase-equilibria and cooling-rate studies D. WALKER; D. WALKER 1Hoffman Laboratory, Harvard University, Cambridge, Massachusetts 02138 Search for other works by this author on: GSW Google Scholar R. J. KIRKPATRICK; R. J. KIRKPATRICK 1Hoffman Laboratory, Harvard University, Cambridge, Massachusetts 02138 Search for other works by this author on: GSW Google Scholar J. LONGHI; J. LONGHI 1Hoffman Laboratory, Harvard University, Cambridge, Massachusetts 02138 Search for other works by this author on: GSW Google Scholar J. F. HAYS J. F. HAYS 1Hoffman Laboratory, Harvard University, Cambridge, Massachusetts 02138 Search for other works by this author on: GSW Google Scholar Author and Article Information D. WALKER 1Hoffman Laboratory, Harvard University, Cambridge, Massachusetts 02138 R. J. KIRKPATRICK 1Hoffman Laboratory, Harvard University, Cambridge, Massachusetts 02138 J. LONGHI 1Hoffman Laboratory, Harvard University, Cambridge, Massachusetts 02138 J. F. HAYS 1Hoffman Laboratory, Harvard University, Cambridge, Massachusetts 02138 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1976) 87 (5): 646–656. https://doi.org/10.1130/0016-7606(1976)87<646:CHOLPB>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation D. WALKER, R. J. KIRKPATRICK, J. LONGHI, J. F. HAYS; Crystallization history of lunar picritic basalt sample 12002: Phase-equilibria and cooling-rate studies. GSA Bulletin 1976;; 87 (5): 646–656. doi: https://doi.org/10.1130/0016-7606(1976)87<646:CHOLPB>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Experimental crystallization of a lunar picrite composition (sample 12002) at controlled linear cooling rates produces systematic changes in the temperature at which crystalline phases appear, in the texture, and in crystal morphology as a function of cooling rate. Phases crystallize in the order olivine, chromium spinel, pyroxene, plagioclase, and ilmenite during equilibrium crystallization, but ilmenite and plagioclase reverse their order of appearance and silica crystallizes in the groundmass during controlled cooling experiments. The partition of iron and magnesium between olivine and liquid (KD = 0.33) is independent of cooling rate (0.5° to 2000°C/hr), temperature (1325° to 600°C), and pressure (0 to 12 kb). Comparison of the olivine nucleation densities in the lunar sample and in the experiments indicates that the sample began cooling at about l°C/hr. Pyroxene size, chemistry, and growth instability spacings ("swallowtails"), as well as groundmass coarseness, all suggest that the cooling rate subsequently decreased by as much as a factor of 10 or more. The porphyritic texture of this sample, then, is produced at a decreasing, rather than a discontinuously increasing, cooling rate. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.