Geo-Note 2006-01

Geo-Note 2006-01

GEO 2006-01

Petrography and geochronology of crustal xenoliths from northern Alberta kimberlite

Representative crustal xenoliths from kimberlite pipes in the Buffalo Head Hills and Birch Mountains kimberlite fields of northern Alberta provide insight into the crystalline basement of the Buffalo Head domain and Taltson magmatic zone, respectively.

Crustal xenoliths from the K11 kimberlite, Buffalo Head Hills kimberlite field, are dominated by olivine-biotite orthopyroxenite and breccia that are either altered, or completed replaced, by pseudomorphic bastite serpentine and antigorite. A crustal xenolith from the K6 kimberlite, Buffalo Head Hills kimberlite field, is a quartz diorite dominated by plagioclase with less abundant intergrowth of kaolinite-quartz and minor biotite, magnetite/hematite, ilmenite and K-feldspar. A basement xenolith from the Kendu kimberlite, Birch Mountains kimberlite field, is a metamorphosed monzonite that is dominated by plagioclase with lesser orthopyroxene and K-feldspar.

U-Pb laser ablation isotopic analysis was completed on zircon from crustal xenoliths from kimberlite within the Buffalo Head Hills and Birch Mountains kimberlite fields. This allows for comparison between crustal rocks situated within Buffalo Head domain and Taltson magmatic zone, respectively. Zircon U-Pb ages of between ca. 1919 Ma and 1955 Ma were obtained from zircon U-Pb in both areas. This strongly supports the contention of a significant event in the Buffalo Head domain at ca. 1940 Ma. Similarities between the Buffalo Head domain and Taltson magmatic zone will have significant implication on future Alberta basement domain models.

Eccles, D.R., Payne, J.G., Simonetti, A. and Hood, C.T.S. (2006): Petrography and geochronology of crustal xenoliths from northern Alberta kimberlite; Alberta Energy and Utilities Board, EUB/AGS Geo-Note 2006-01, 24 p.