The age and origin of megacrysts in the Jericho kimberlite (Nunavut, Canada) ...

• Main Author: Marković, Goran
• Format: Text
• Language: English
• Published: University of British Columbia 2011
• Subjects: Nunavut
• Online Access: https://dx.doi.org/10.14288/1.0052569; https://doi.library.ubc.ca/10.14288/1.0052569

Fourteen samples of megacrysts from Jericho kimberlite have been studied. The study includes petrography, geochemistry of major and minor elements, thermobarometry and Sr-Nd-Hf isotopic analyses. The purpose of the study is to determine the relationship between megacrysts and kimberlites (xenocrystal vs cognate) and shed light on the nature of melts parental to kimberlite megacrysts. The Jericho megacrysts include garnet, clinopyroxene, olivine, ilmenite and orthopyroxene. A unique feature of Jericho megacrysts is its gradual transition from discrete megacrysts to megacrystalline pyroxenites. Equilibrium temperatures and pressures were calculated for eight megacryst samples. All calculated P-T place megacrysts into deep garnet-bearing mantle, with T=1200-1280° C and P=60-71 kbar. The P-T estimates for orthopyroxene-bearing samples are identical to P-T estimates for orthopyroxene-free samples, with 195-230 km depth range. Thermobarometric data on Jericho megacrysts cannot give a definitive answer about their ...