A common parentage-low abundance trace element data of gem diamonds reveals similar fluids to fibrous diamonds M.Y. Krebs a, ⁎, D.G. Pearson a , T. Stachel a,b , F. Laiginhas c , S. Woodland a , I. Chinn d , J. Kong e a Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Canada b Canadian Centre for Isotopic Microanalysis, University of Alberta, Edmonton, Canada c Department of Earth Sciences, Durham University, UK d De Beers Group Exploration, South Africa e De Beers, Canada abstract article info Article history: Received 19 July 2018 Accepted 20 November 2018 Available online 23 November 2018 Quantitative trace element data from high-purity gem diamonds from the Victor Mine, Ontario, Canada as well as near-gem diamonds from peridotite and eclogite xenoliths from the Finsch and Newlands mines, South Africa, acquired using an off-line laser ablation method show that we see the same spectrum of fluids in both high-purity gem and near-gem diamonds that was previously documented in fibrous diamonds. “Planed” and “ribbed” trace element patterns characterize not only the high-density fluid (HDF) inclusions in fibrous diamonds but also in gem diamonds. Two diamonds from two Finsch harzburgite xenoliths show trace element patterns similar to those of saline fluids, documenting the involvement of saline fluids in the precip- itation of gem diamonds, further strengthening the link between the parental fluids of both gem and fibrous diamonds. Differences in trace element characteristics are evident between Victor diamonds containing silicate inclusions compared with Victor diamonds containing sulphide inclusions. The sulphide-bearing diamonds show lower levels of inter-element fractionation and more widely varying siderophile element concentrations - indicating that the silicate and sulphide-bearing diamonds likely formed by gradations of the same processes, via melt-rock reaction or from a subtly different fluid source. The shallow negative LREE N -HREE N slopes displayed by the Victor diamonds establish a signature indicative of original derivation of the diamond forming agent during major melting (~10% melt). Consequently, this signature must have been passed on to HDFs sep- arating from such silicate melts. © 2018 Elsevier B.V. All rights reserved. Keywords: Trace elements Diamond Laser ablation Diamond HDFs Victor diamond mine 1. Introduction Diamond crystallizes from a fluid/melt phase - relics of which may become trapped and, thus preserved in the form of inclusions (Navon et al., 1988). To understand the origin of diamonds it is essential to constrain the nature of these so-called high-density fluid (HDF) in- clusions. Fibrous and “cloudy” diamonds trap a high number of HDF inclusions and, therefore, have been extensively studied using major and trace element compositions, resulting in the identification of four major compositional types of HDFs (saline, high-Mg and low- Mg carbonatitic, and silicic) that form two compositional arrays. One array extends between the saline and high-Mg carbonatitic end- members and a second ranges from low-Mg carbonatitic to the silicic end-member (e.g., Izraeli et al., 2001; Klein-Bendavid et al., 2007; Navon et al., 1988; Tomlinson et al., 2006; Weiss et al., 2009). Trace element patterns of diamond HDFs have been classified into two end-members: “planed” (fairly flat and unfractionated) and “ribbed” (highly fractionated) (e.g., Tomlinson et al., 2009; Weiss et al., 2009, 2011; Klein-Bendavid et al., 2010; Smith et al., 2012). The planed patterns can be related to an asthenospheric source whereas the ribbed patterns are proposed to represent increased in- teraction with the sub-continental lithospheric mantle (Weiss et al., 2013). It is important to note that while the composition of HDFs trapped inside fibrous diamond is well constrained, their exact nature and com- position at the time of entrapment/diamond formation is still subject to extensive research. The general consensus is that primary HDFs are high-density fluids, highly enriched in carbon and water, whose chem- ical nature is similar to supercritical liquids with melt-like solubilities (Klein Ben-David et al., 2006; Weiss et al., 2010). Bureau et al. (2012) Lithos 324–325 (2019) 356–370 ⁎ Corresponding author at: Gemological Institute of America, 4th Floor, 50 West 47th Street, 10036 New York, NY, USA. E-mail address: mkrebs@gia.edu (M.Y. Krebs). https://doi.org/10.1016/j.lithos.2018.11.025 0024-4937/© 2018 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Lithos journal homepage: www.elsevier.com/locate/lithos