SalFluMa · Saline Fluids in the Mantle - Experimental Investigation of Their Role in Diamond Formation and Kimberlite Magmatism

Saline Fluids in the Mantle - Experimental Investigation of Their Role in Diamond Formation and Kimberlite Magmatism

The majority of natural diamonds that have great economic importance for the gem industry are formed at great depth beneath old continents in the subcontinental lithospheric mantle (SCLM). The main carrier of these diamonds are kimberlites, volcanic rocks that transport fragments of the SCLM to the Earth’s surface. Both diamond formation and kimberlite genesis are still heavily debated processes in the Earth sciences. Growing evidence from natural samples, such as fluid inclusions in diamonds, suggest that Cl-bearing (i.e., saline) fluids may play an important role in diamond formation and possibly in kimberlite generation. These saline fluids are envisaged to percolate into the SCLM from slabs of oceanic crust subducted under continents. The main objectives of the SalFluMa project can be divided into the following research questions: 1. What is the nature of reactions between saline fluids and the SCLM? The project has successfully tested existing hypotheses for the formation of diamond-forming fluids by high-pressure, high-temperature experiments. Two distinct reactions between saline fluids and SCLM lithologies were investigated: a) saline fluids reacting with peridotite (i.e., lherzolite, harzburgite) to produce carbonatitic melts, and b) saline fluids reacting with eclogite to produce silicic melts. Our experiments have shown that these hypotheses are valid and could further explain compositional trends observed in other phases from kimberlites. 2. Can the introduction of saline fluids into the SCLM trigger kimberlite magmatism? Based on previous studies, a genetic link between the diamond-forming saline fluids and primary kimberlite melt seems plausible. This study has shed new light on this link by demonstrating a similarity in composition of melts resulting from the reaction of saline fluids with the SCLM to previous estimates of primary melts of kimberlites. This has underlined the possible involvement of saline fluids in the generation of kimberlites. In summary, this project has significantly advanced our understanding of saline fluids in the mantle. Such fluids have recently gained more attention as a potent metasomatic agent in the SCLM (i.e., able to change the chemical characteristics of the ambient mantle). However, this notion was mostly based on observations on natural samples. The experiments performed here are thus not only completely novel, they are also indispensable in testing existing hypothetical models dealing with various mantle processes, including subduction zone processes, mantle metasomatism, diamond formation, and kimberlite magmatism. The Institute for Mineralogy at the University of Münster was an excellent match for this kind of research due to its outstanding research facilities and personnel. Realizing the project at the University of Münster should reinforce its reputation as a leading institute for mantle research in Europe.

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз