Chromian spinel mineralogy of the Staré Ransko gabbro-peridotite,Czech Republic,and its implications for sulfide mineralization |
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Authors: | A H van der Veen P Maaskant |
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Institution: | (1) Faculty of Earth Sciences, Department of Geology, University of Utrecht, P.O. Box 80.021, 3508 TA Utrecht, The Netherlands;(2) Institute of Earth Sciences, Vrije Universiteit, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands |
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Abstract: | Chromian spinels from the Staré Ransko gabbro-peridotite, Czech Republic, display a distinct development trend: from primary Cr-rich spinels towards ferro-ferri (Ti-enriched magnetite) and magnesio-alumina (spinel sensu stricto) spinels. Zoning in the spinels is thought to be the result of a combination of exsolution, postdepositional diffusion and replacement processes. Multiphase, globular silicate inclusions — mainly biotite and amphibole, also orthopyroxene, serpentine and chlorite — are present in euhedral, largely homogeneous chromian spinels which occur in a matrix of poikilitic amphibole. The enclosed minerals have similar compositions to the minerals in the host rock. These silicate inclusions are interpreted as being due to a late magmatic introduction of a hydrous K-Ca-rich melt phase, contaminated by wall-rock interaction, into a semi-solidified olivine (± pyroxenes) cumulate.The composition of the chromian spinel may be used as an indicator for sulfide mineralization conditions (Johan 1979). The data reported in this paper are compatible with Johan's model. |
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