Experimental study of syngenetic relations of diamond and its inclusions in the heterogeneous system eclogite-carbonatite-sulfide-diamond at 7.0 GPa

 

Vasiliev, P.*, Okoemova, V.*, Litvin Y.A**, Bobrov A.*

*Geological Faculty, Moscow State University, Russia

**Institute of Experimental Mineralogy, Chernogolovka, Russia

prokvasiliev@gmail.com

 

The role of physicochemical experiment is decisive for understanding of chemical and phase state of mantle diamond-forming media [1]. Application of the criterion of syngenesis of diamonds and primary inclusions is special importance for investigation of the systems with compositions similar to natural multi-component diamond-forming media. We studied melting relations for syngenesis of diamond and inclusions in the system eclogite (garnet +clinopyroxene) – K-Mg-Ca-carbonatite – sulfide (mixture of pyrrhotite, pentlandite, and chalcopyrite) – diamond at 7.0 GPa by the analysis of a fragment of the syngenesis diagram within the pseudo-binary section eclogite50-carbonatite50-diamond. The main element of this diagram is the curve of diamond solubility in completely miscible carbonate-silicate melts depending on temperature. The diagram shows melting relations in carbon-saturated diamond-forming carbonate-silicate melts with silicate (garnet and clinopyroxene) and carbonate (magnesite, aragonite, and K-carbonate) mineral phases.

The syngenesis diagram for the sulfide-diamond system contains the curve of diamond solubility in sulfide melts depending on temperature and demonstrates the areas where diamond growing in carbon-sulfide melts captures inclusions of sulfide melts and minerals. The general diagram of the multi-component eclogite-carbonatite-sulfide-diamond systems is a combination of two discussed diagrams. It demonstrates two curves of diamond solubility in sulfide and carbonate-silicate melts. The results obtained provide evidence for complete immiscibility of carbonate-silicate and sulfide components of parental melts and predominant crystallization of diamond in carbonate-silicate media. This is consistent with the carbonatite (carbonate-silicate) model of diamond genesis [1].

 

This study was financially supported by RFBR grants 08-05-00110 and 09-05-00751

 

References:

[1] Litvin, Y.A. (2007) in Ohtani, E., ed., Advances in High-Pressure Mineralogy: Geological Society of America Special Paper 421,  High-pressure mineralogy of diamond genesis, 83-103.