Trace-element patterns of fibrous and monocrystalline diamonds: Insights into mantle fluids

Ancient mantle metasomatism recorded in subcalcic garnet xenocrysts: Temporal links between mantle metasomatism, diamond growth and crustal tectonomagmatism

“…They range in major element composition from saline to carbonatitic to silicic and have highly fractionated REE patterns as a common feature (e.g. Schrauder and Navon, 1994;Tomlinson and Mueller, 2009;Klein-BenDavid et al, 2014;Rege et al, 2010). These decrease steeply from La to Dy and then level off towards Lu (Fig.…”

The growth of fibrous, cloudy and polycrystalline diamonds

“…Recent publications have shown that the trace element content of some gem diamonds share many similarities with those of fibrous diamonds (Araujo et al, 2009;McNeill et al, 2009), suggesting that the growth mechanisms involving fibrous and some monocrystalline diamonds may be similar. This is also discussed by Rege et al (2010) on the basis of a detailed trace element comparison of fibrous and monocrystalline diamonds from various origins. They identified two general types of patterns termed fibrous high (FH) and fibrous low (FL, see above).…”

“…Klein-BenDavid et al, 2007a,b, 2009Tomlinson et al, 2009 and references therein;Weiss et al, 2009;Klein-BenDavid et al, 2010;Rege et al, 2010). Most of these studies have concluded that at least two fluids (a carbonatitic and silicic endmember or a saline endmember) would be necessary to be in equilibrium with the growing diamonds to generate the compositional variety of the inclusions trapped in the fibrous coats.…”

“…For example, considering the nitrogen composition of the diamonds and the trace element composition of their inclusions, Weiss et al (2009) have identified a radial compositional zonation of the inclusions, which they explained by successive growth events from different fluids, resulting from the interaction of saline fluids either with peridotites or eclogites. In a large scale study of trace element compositions of worldwide diamonds (fibrous and monocrystalline), Rege et al (2010) have defined two populations based on trace element compositions, a "fibrous high" with high contents of LREE, Ba and K, and a "fibrous low" characterized by depletion in LREE/MREE, Ba and K, negative anomalies in Sr and Y. They proposed a model of carbonatite-silicate immiscibility leaving a hydrous silicate member with a trace element signature observed in most of the crystalline diamonds (fibrous low), whereas the carbonatitic member would present a trace element fingerprint similar to the coats of diamonds (fibrous high).…”

“…They proposed a model of carbonatite-silicate immiscibility leaving a hydrous silicate member with a trace element signature observed in most of the crystalline diamonds (fibrous low), whereas the carbonatitic member would present a trace element fingerprint similar to the coats of diamonds (fibrous high). The silicate member has more similarities with the hydrosilicic high-density fluids trapped in fibrous diamonds, but there are still differences between the trace element signature of most monocrystalline diamonds and high-density fluids (Rege et al, 2010). Additional studies are necessary to better understand diamond growth processes in fluids.…”