Trace element geochemistry of Amba Dongar carbonatite complex,India: Evidence for fractional crystallization and silicate-carbonate melt immiscibility |
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| Authors: | Jyotiranjan S Ray P N Shukla |
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| Institution: | (1) Physical Research Laboratory, 380 009 Navrangpura, Ahmedabad, India |
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| Abstract: | Carbonatites are believed to have crystallized either from mantle-derived primary carbonate magmas or from secondary melts
derived from carbonated silicate magmas through liquid immiscibility or from residual melts of fractional crystallization
of silicate magmas. Although the observed coexistence of carbonatites and alkaline silicate rocks in most complexes, their
coeval emplacement in many, and overlapping initial87Sr/86Sr and143Nd/144Nd ratios are supportive of their cogenesis; there have been few efforts to devise a quantitative method to identify the magmatic
processes. In the present study we have made an attempt to accomplish this by modeling the trace element contents of carbonatites
and coeval alkaline silicate rocks of Amba Dongar complex, India. Trace element data suggest that the carbonatites and alkaline
silicate rocks of this complex are products of fractional crystallization of two separate parental melts. Using the available
silicate melt-carbonate melt partition coefficients for various trace elements, and the observed data from carbonatites, we
have tried to simulate trace element distribution pattern for the parental silicate melt. The results of the modeling not
only support the hypothesis of silicate-carbonate melt immiscibility for the evolution of Amba Dongar but also establish a
procedure to test the above hypothesis in such complexes. |
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| Keywords: | Carbonatite Amba Dongar India liquid immiscibility trace elements REE |
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