|
|||||
|
|
Petrology of sapphirine granulite and associated sodic gneisses from the Indian Head Range, Newfoundland |
|
| Authors: | J V Owen F J Longstaffe J D Greenough |
| Institution: | a Department of Geology, Saint Mary's University, Halifax, Nova Scotia, Canada B3H 3C3 b Department of Earth Sciences, The University of Western Ontario, London, Ontario, Canada N6A 5B7 c Department of Geology, Okanagan University College, Kelowna, British Columbia, Canada V1V 1V7 |
| Abstract: | Migmatitic granulites from the Indian Head Range (IHR) are dominated by granoblastic, Opx-bearing (quartz) dioritic gneiss with subordinate garnet+orthopyroxene+biotite+albite (±quartz±microcline±cordierite±sillimanite) gneiss and comparatively biotite-rich, sapphirine+cordierite+orthopyroxene+albite (±microcline±sillimanite±corundum) gneiss. The latter contains at least two generations of sapphirine and cordierite, one apparently predating migmatization, the other associated with or following this event. Mineral thermobarometers yield temperatures up to  800 °C at 8 kbar. The IHR granulites have very high δ18O values (+10.8 to +14.5) which most likely indicate a sedimentary precursor. Their REE and HFSE contents resemble the trace element signature of post-Archean Australian shale (PAAS). Lithological analogues from other Grenvillian inliers in western Newfoundland have similar oxygen isotopic and immobile-element signatures. They too are interpreted as metasedimentary rocks. The IHR rocks, however, have unusually sodic compositions (e.g., Na2O/CaO and Na2O/K2O=2.1–22.5 and 0.93–13.8, respectively) and contain albite or sodic oligoclase despite their high metamorphic grade. The geochemical data indicate that these rocks were albitized prior to high-grade metamorphism. No counterpart of this event is recorded in granulites from the other inliers, indicating that the IHR may be highly allochthonous with respect to these other Grenvillian terranes. |
| Keywords: | Sapphirine granulite Sodic gneisses Indian Head Range |
| 本文献已被 ScienceDirect 等数据库收录！ | |