Isotope systematics of secondary minerals from the Prospect Intrusion,New South Wales |
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Authors: | M. L. Williams P. F. Carr |
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Affiliation: | 1. School of Earth and Environmental Sciences , University of Wollongong , NSW, 2522, Australia mlw02@uow.edu.au;3. School of Earth and Environmental Sciences , University of Wollongong , NSW, 2522, Australia |
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Abstract: | The differentiated Mesozoic alkali dolerite Prospect Intrusion contains a wide range of secondary minerals, including carbonates (primarily calcite), laumontite, prehnite and heulandite, whose stability relationships imply a formation temperature of <200°C. The δ18O data for carbonates define a higher temperature (160 – 195°C) suite, and a lower temperature (51 – 73°C) suite. The δ13C, δ18O and 87Sr/86Sr isotope systematics for these carbonates suggest derivation of the higher temperature group from magmatic fluids, whereas the other group had a major meteoric component that probably originated from porewater in the country rock. Source fluids for prehnite were meteoric rather than magmatic in origin based on their δD and δ18O ratios. Early in the intrusion's emplacement, CO2-rich hydrothermal fluids formed a carbonate rind sealing the upper part of the hydrothermal system and produced the higher temperature carbonates (calcite) and laumontite. Later, cooler fluids with a meteoric component infiltrated vesicles and fractures, depositing the lower temperature carbonates (calcite, aragonite), heulandite and prehnite. |
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Keywords: | calcite carbon hydrothermal alteration oxygen prehnite Prospect Intrusion secondary minerals stable isotopes |
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