Genesis of high-zinc chromite and associated cobalt-mineralized blackwall in the Sykesville District, Maryland piedmont
Zone, Zn-bearing chromites occur in a serpentinized ultramafite (UM), pelitic schists, the associated blackwall, and a banded Fe oxide-quartz rock (BIR). The spinels are associated with Fe-Cu-Co mineralization in the Sykesville District of the Maryland Piedmont. Within most grains, three main zones can be distinguished based on optical properties and chemistry. The marked discontinuity between the central core and the middle zone (ferrit-chromite (FC)) and the anhedral form of the core suggest that the FC developed by the irreversible dissolution of the core and reprecipitation of FC as a mantle. The outer magnetite zone was added during the latter stages of serpentinization as chemical communication with the original spinel core ceased. The highest Zn contents occur in the spinel cores near the boundary with the FC. ZnO contents of up to 19 wt.% have been measured. To the authors knowledge, these are the highest reported concentrations of Zn in chromite. The Zn/Mg ratio in the spinel cores correlates closely with the host rock mineralogy such that /mu//sub ZnMg/ decreases monotonically from the pelite into the UM. The occurrence of chromite in all rock units and the strong field association between the UM and the BIR suggest that UM material was present on the seafloor. Based on chemical and textural evidence, the authors postulate that Zn was introduced during the earliest stages of the hydrothermal processes accompanying serpentinization and mineralization in a subaqueous environment. Cu and Zn were probably supplied by a seafloor hydrothermal system, and the BIR and Co were produced alteration of the UM unit.
- Research Organization:
- Univ. of Maryland, College Park (USA)
- OSTI ID:
- 5944768
- Report Number(s):
- CONF-8510489-
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Vol. 17; Conference: 98. annual meeting of the Geological Society of America, Orlando, FL, USA, 28-31 Oct 1985
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
58 GEOSCIENCES
HYDROTHERMAL SYSTEMS
ROCK-FLUID INTERACTIONS
MARYLAND
SCHISTS
CHEMICAL COMPOSITION
MINERALOGY
PETROGENESIS
COBALT ORES
COPPER ORES
GEOCHEMISTRY
GEOLOGIC HISTORY
IRON ORES
MINERALIZATION
OPTICAL PROPERTIES
PETROLOGY
QUANTITATIVE CHEMICAL ANALYSIS
SERPENTINE
SPINELS
ZINC COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CHALCOGENIDES
CHEMICAL ANALYSIS
CHEMISTRY
ENERGY SYSTEMS
FEDERAL REGION III
GEOLOGY
GEOTHERMAL SYSTEMS
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
METAMORPHIC ROCKS
MINERALS
NORTH AMERICA
ORES
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
ROCKS
SILICATE MINERALS
USA
152003* - Geothermal Data & Theory- Rock-Water-Gas Interactions
580300 - Mineralogy
Petrology
& Rock Mechanics- (-1989)
580400 - Geochemistry- (-1989)