Larry, you have brought up some excellent points and references!
I haven't enough time right now to address this adequately; nonetheless your comments on Ashton's NR references are highly pertinent.
From ACA's past NR:
"After penetrating 34 metres (113 feet) of glacial sediments the first vertical diamond drill hole on anomaly 7B passed into olivine-dominated fragmental and tuffaceous material displaying possible crater and diatreme facies textures. The drill hole remained in this volcanic-textured material until termination at 154 metres (505 feet)."
This description by Ashton of encountered material, among other of their reports you pointed out, rings familiar here (MMU's last NR: biz.yahoo.com ).
Also, see the descriptions made in ACA's paper presented at the IKC last year (Apr./98), including:
The Buffalo Hills Kimberlite Province, North-central Alberta, Canada
victoryventures.com
"Initial petrological studies of the Buffalo Hills kimberlites indicate that all material recovered to date is crater facies. A diatreme-facies component has not as yet been identified in drill core from depths of up to 200 m. Volcanic stratigraphy is dominated by lapilli-bearing olivine crystal tuffs, occasionally with well-defined, generally normally-graded beds varying from coarse ash to coarse crystal. Juvenile lapilli-rich beds and rare autoliths have also been noted, particularly in kimberlites K6, K91, and K14, and minor interfingering sedimentary beds have been identified in drill holes from several pipes. Lapilli are generally spherical or amoeboid in form, with the former frequently nucleated on olivine macrocrysts; vesicles are a common feature of many amoeboid lapilli. Crytsal xenoliths are typically shales of the Shaftesbury formation and commonly display margins embayed by olivine grains, suggesting an un- or semi-lithified state (for the host rock) during kimberlite emplacement. In several pipes, silica alteration erases primary textures in the uppermost parts of the sequence, while bitumen is abundant as fracture infillings throughout some of the kimberlites."
- this is a significant paper to review (go to the above link to read it all)
Another such paper, published by Marum's hired ADP specialist, APEX Geoscience Ltd. (including Marum's head field Geologist, Mike Dufresne):
An Update on the Newly Emerging Diamondiferous Kimberlite Field in Western Canada
victoryventures.com
- a paper well-worth reviewing
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>>The question is, are we talking diatreme facies in Marums case; does the Ashton information confirm an association with the Marum find and so what?<<
So far, as in the above IKC paper excerpt, Ashton has only described their encountered volcanic host-rock as "crater facies." - And yes, I think there is an association, tho perhaps a different environment in terms of deposition. -- See MMU president Boulay's comments made prior to the current drill program, Nov./98:
Message 6469097
"We employ a biostratigraphic consultant to look at our core. Fossils in our core confirm that our kimberlite component minerals are residual grains in a Cretaceous age (approx 85 million years old) rock, are derived from a nearby source, and are not glacial in origin. What we don't know is that if it is a crater facies rock, a volcanic ash dump, a reworked lag deposit or another type of deposit associated with explosive volcanic activity. The situation to the east where Ashton and Montello are drilling is simpler in that the kimberlites blew out into a shallow sea, maybe 100 to 150 metres deep and the ejecta fell back to form more or less organized beds. The Chinchaga was coastal marsh to sub-areal (i.e., exposed land) and we can expect a more complicated re-depositional picture. As to the "pipe" question, it's still early days. Neither Ashton nor Montello (I believe) have encountered diatreme facies rocks and the current list of known pipes may not really be pipes at all but suspended craters with the underlying pipes having been been destroyed by the inward collapse of marine muds. No one knows at this stage."
- - - - - -
Also Larry, your findings re. the Orapa deposit are highly significant. Thanks-- I will review them more later!
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Other germane references to lapilli:
Trillion Resources discovers Zimbabwean kimberlite
trillion-resources.com
Diamond Volcanology!
iinet.net.au
-one more relevant link:
River Ranch Limited
utande.co.zw
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I also hope we hear back from Rick Boulay on your keen questions/comments, Larry!
Best Regards,
-j
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