Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Nabelek, P. I. Search for Related Content GeoRef GeoRef Citation

Quartz-sillimanite leucosomes in high-grade schists, Black Hills, South Dakota: A perspective on the mobility of Al in high-grade metamorphic rocks

¹ Department of Geological Sciences, University of Missouri–Columbia, Columbia, Missouri 65211

In the Black Hills, South Dakota, anatectic migmatites that formed above the second sillimanite isograd comprise mesosomes dominated by quartz, biotite, sillimanite, plagioclase, and sporadic poikiloblasts of K-feldspar, melanosomes dominated by biotite and sillimanite, and leucosomes. Some leucosomes have near-minimum granite composition, but many lack alkali elements and have fibrolitic sillimanite instead of feldspar. The proportion of Si/Al is the same in both leucosome types. The sillimanite-containing leucosomes include fluorapatite, which indicates high activity of F. The lack of alkali feldspar in these leucosomes is attributed to its instability relative to sillimanite + quartz in the presence of fluids with high a_H⁺/a_K⁺ ratios that evolved from the crystallizing leucosomes. It is suggested that quartz-aluminosilicate segregations and veins in other high-grade terranes may also represent pegmatitic melts in which alkali feldspar crystallization was inhibited by high activities of hydrogen, resulting in loss of alkali elements.

This article has been cited by other articles:

				P. Louvat, S. R. Gislason, and C. J. Allegre Chemical and mechanical erosion rates in Iceland as deduced from river dissolved and solid material Am J Sci, May 1, 2008; 308(5): 679 - 726. [Abstract] [Full Text] [PDF]

				P. I. Nabelek, T. C. Labotka, T. Helms, and M. Wilke Fluid-mediated polymetamorphism related to Proterozoic collision of Archean Wyoming and Superior provinces in the Black Hills, South Dakota American Mineralogist, October 1, 2006; 91(10): 1473 - 1487. [Abstract] [Full Text] [PDF]

				T. E. JOHNSON, R. L. GIBSON, M. BROWN, I. S. BUICK, and I. CARTWRIGHT Partial Melting of Metapelitic Rocks Beneath the Bushveld Complex, South Africa J. Petrology, May 1, 2003; 44(5): 789 - 813. [Abstract] [Full Text] [PDF]

				M. Wilke, P. I. Nabelek, and M. D. Glascock B and Li in Proterozoic metapelites from the Black Hills, U.S.A.: Implications for the origin of leucogranitic magmas American Mineralogist, April 1, 2002; 87(4): 491 - 500. [Abstract] [Full Text] [PDF]

				A. Stefansson and S. R. Gislason Chemical Weathering of Basalts, Southwest Iceland: Effect of Rock Crystallinity and Secondary Minerals on Chemical Fluxes to the Ocean Am J Sci, June 1, 2001; 301(6): 513 - 556. [Abstract] [Full Text] [PDF]

				P. I. Nabelek, M. Sirbescu, and M. Liu Petrogenesis and tectonic context of the Harney Peak Granite, Black Hills, South Dakota Rocky Mountain Geology, November 1, 1999; 34(2): 165 - 181. [Abstract] [Full Text] [PDF]