Katharine Masun HBSc thesis abstract

Thesis Title: 
Crater Facies Kimberlites

The Yubileinaya kimberlite pipe, discovered in 1957, is located within the central part of the Alakit kimberlite field of the Yakutian diamondiferous Province.  The Yakutian Province is located within the East Siberia Platform.  Host rocks include Lower-Middle Ordovician and Lower Silurian terrigenous-carbonate sequences.  The pipe is overlain entirely by Permo-Carboniferous sediments and Lower Triassic tuffs.  The intrusion consists of at least two different kimberlite types.  An initial injection of volcaniclastic kimberlite breccia has been intruded by a macrocrystal hypabyssal kimberlite forming distinct central channel which flares rapidly outward in the upper portion of the kimberlite.

This study of the Yubileinaya intrusion was limited to the macroscopic and microscopic investigation of a single hand specimen by transmitted light and electron microscopy.  Associated rocks and geological relationships were not observed.

The hand specimen examined is typical of Group I or archetypal kimberlite, containing rounded macrocrysts of pseudomorphed olivine, common macrocrysts of mica and rare garnet together with groundmass serpentine, spinel, apatite, perovskite and carbonate.  Texturally, the hand specimen comprises crater facies kimberlite with a conspicuous alternation of two distinct units.  Clast-supported, volcaniclastic sandstone alternate with crypto-crystalline, pelitic carbonate mudstone.  The former represents pyroclastic airfall lapilli tuffs and coarse ash, composed primarily of juvenile lapilli which have undergone little or no reworking.  The latter unit can be termed a volcaniclastic kimberlitic mudstone, as its genesis is unclear.