caa a22 4500 465791476 CHVBK 20180323112026.0 cr unu---uuuuu 170327e19901101xx s 000 0 eng 10.1007/BF00306536 doi (NATIONALLICENCE)springer-10.1007/BF00306536 Geochemistry and origin of Archaean quartz-cordierite gneisses from the Godthåbsfjord region, West Greenland [Elektronische Daten] [Robert Dymek, Michael Smith] We report new data on the major, minor and trace element compositions of metasedimentary quartzcordierite gneisses (QCG), an important member of the Archaean Malene supracrustal suite found throughout the Godthåbsfjord region of West Greenland. The analyzed QCG contain assemblages of quartz+cordierite+biotite±garnet±anthophyllite/gedrite±staurolite±sillimanite±plagioclase (with abundant accessory zircon, and minor rutile, monazite and allanite), and broadly resemble cordierite-orthoamphibole rocks found in a great number of other metamorphic terrains. Chemically, the QCG are characterized by: (1) high but variable SiO2 (59-87 wt%), relative enrichments in MgO, FeO, and Al2O3 (mg∼0.35-0.85), and depletions in Na2O, K2O and especially CaO; (2) low concentrations of Sc, Cr, Co, Ni, and Sr; (3) high concentrations of Y, Nb, Zr, Hf, Ta, Th, U, and REE (rare earth elements)-with prominent negative Eu-anomalies in each case; (5) high concentrations of Ga (18-55 ppm), with variable Ga/Al ratios that are significantly higher than average crustal material. Low Cr and Ni, together with enriched and fractionated REE (displaying negative Eu-anomalies), distinguish the Malene QCG from published accounts of most other Archaean sedimentary rocks. Furthermore, all of the above-mentioned trace element characteristics distinguish the QCG from "ordinary” Malene clastic metasediments (quartzites, psammites, and pelites), suggesting a separate origin for the QCG. These data point towards chemically evolved felsic igneous rocks being the source of the QCG. Consequently, we propose that the Malene QCG represent metamorphosed felsic volcaniclastic sediments that underwent hydrothermal alteration by heated seawater prior to metamorphism, which resulted in gain of Mg (and Fe?), loss of alkalis and lime, and possibly Eu and Sr. The overall trace-element characteristics of the QCG (elevated Ga, Zr, Nb, REE, etc.) are features shared by A-type granites and their volcanic equivalents. Such igneous rocks may represent the ultimate source material for the QCG protolith. Springer-Verlag, 1990 Dymek Robert Department of Earth & Planetary Sciences, Washington University, 63130, St. Louis, MO, USA aut Smith Michael Department of Earth & Planetary Sciences, Washington University, 63130, St. Louis, MO, USA aut Contributions to Mineralogy and Petrology Springer-Verlag 105/6(1990-11-01), 715-730 0010-7999 105:6<715 1990 105 410 https://doi.org/10.1007/BF00306536 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00306536 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Dymek Robert Department of Earth & Planetary Sciences, Washington University, 63130, St. Louis, MO, USA aut NATIONALLICENCE 700 1- Smith Michael Department of Earth & Planetary Sciences, Washington University, 63130, St. Louis, MO, USA aut NATIONALLICENCE 773 0- Contributions to Mineralogy and Petrology Springer-Verlag 105/6(1990-11-01), 715-730 0010-7999 105:6<715 1990 105 410 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer