Hypersthene-ilmenite(/magnetite) symplectites in coronitic olivine-gabbronorites |
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| Authors: | HP Zeck HH Shenouda JG Rønsbo RPE Poorter |
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| Institution: | 1. Institute of Petrology, Copenhagen University, Øster Voldgade 10, 1350 Copenhagen K, Denmark;2. Institute of Mineralogy, Copenhagen University, Øster Voldgade 5, 1350 Copenhagen K, Denmark;3. Vening Meinesz Laboratory, Utrecht University, Budapestlaan 4, 3584 CD, Utrecht, Holland |
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| Abstract: | Symplectitic intergrowths of hypersthene (host) with ilmenite and minor magnetite (vermicules) in a gabbroic sill from the Precambrian of southwest Sweden occur as replacement products of olivine, and are thought to have formed simulataneously with the replacement of nearby crystals of ilmenite and Timagnetite by biotite and hornblende (and spinel). These interrelated replacement processes may have taken place during, or immediately after, the final stages of the magmatic crystallization, at temperatures of about 660–680°C, as part of the inherent metamorphism of the gabbroic rock. Another expression of this metamorphic imprint is the occurrence of two-tiered corona shells of hypersthene/hornblende (+spinel) at the interface of olivine and plagioclase crystals. |
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