| Title | Aureoles of Pb(II)-enriched feldspar around monazite in paragneiss and anatectic pods of the Napier Complex, Enderby Land, East Antarctica; the roles of dissolution- reprecipitation and diffusion |
| Author | Grew, E.S.; Yates, M.G.; Wilson, C.J.L. |
| Author Affil | Grew, E.S., University of Maine, Department of Earth Sciences, Orono, ME. Other: University of Melbourne, Australia |
| Source | Contributions to Mineralogy and Petrology, 155(3), p.363-378, . Publisher: Springer International, Heidelberg - New York, International. ISSN: 0010- 7999 |
| Publication Date | Mar. 2008 |
| Notes | In English. 59 refs. GeoRef Acc. No: 288148 |
| Index Terms | Antarctica--East Antarctica; Antarctica--Mount Riiser-Larsen; absolute age; alkali feldspar; Amundsen Bay; anatexis; Antarctica; Archean; aureoles; Casey Bay; chemical composition; crystal chemistry; diffusion; East Antarctica; Enderby Land; enrichment; feldspar group; framework silicates; geochemistry; gneisses; ion probe data; K-feldspar; lead; major elements; mass spectra; metals; metamorphic rocks; metasedimentary rocks; mineral assemblages; mineral composition; monazite; Mount Pardoe; Mount Riiser-Larsen; Napier Complex; paragneiss; petrology; phosphates; Precambrian; precipitation; rare earths; reaction rims; Sakellari Peninsula; Scott Mountains; SHRIMP data; silicates; solution; spectra; textures; Tonagh Island; trace elements; U/Pb; Zircon Point |
| Abstract | Extraordinarily high Pb content in K- feldspar and plagioclase has been found contiguous to monazite in two occurrences in the ultrahigh-temperature Napier Complex of Antarctica. Monazite shows a variety of textures and compositions. In a garnet - sillimanite - orthopyroxene paragneiss at Mount Pardoe (Amundsen Bay), grains range 80- 150 µm across and are anhedral; two grains are Th- and Si-dominant. In pods that crystallized from anatectic melts at 2500 Ma at Zircon Point, Casey Bay, monazite grains range 0.05 mm-1 cm in length and are highly variable in texture. The coarsest grains (›0.7 cm) are skeletal and euhedral, whereas the smallest grains are anhedral and associated with fine- to medium-grained quartz, K-feldspar, plagioclase, garnet, sillimanite and rutile in aggregates that form interstitial veinlets interpreted to be a second generation of anatexis during an event at 1100 Ma. The huttonite component (ThSiO4) reaches 30 mole% in the cores of the coarsest skeletal grains, whereas other grains, particularly smaller ones, show complex and irregular zoning in Th and U. The latter zoning is attributed to dissolution- reprecipitation, which also resulted in complete Pb loss during the 1100 Ma event. (mod. journ. abst.) |
| URL | http://hdl.handle.net/10.1007/s00410-007-0247-z |
| Publication Type | journal article |
| Record ID | 85070 |