Morning DD,
I remember that 1km pipe that pvf and cnb looked at "REDONAO" up in Piaui State (north Bahia project).
the following could also relate to that one possibly.
I took another look at the Read Report to try and grasp a better understanding of how he sees it. Feel free to correct me or disagree with my interpretation.
......"True kimberlite in the project area produce peridotitic and eclogitic garnets, chrome diopsides with compositions consistent with derivation from garnet peridotites and ilmenites that are generally more MgO-RICH than those recovered from the kamafugites.
The Mata da Corda Kamafugites have sampled shallow mantle within the spinel stability field, as opposed to the spinel to garnet transition and garnet stability field sampled by the true kimberlites. THEREFORE,THE KAMAFUGITES SHOULD NOT CONTAIN ANY PERIDOTITIC OR ECLOGITIC GARNET XENOCRYSTS AND THE MOST IMPORTANT INDICATOR FOR THE DISCOVERY OF KIMBERLITE IS GARNET."(my caps)........
My comment: These garnets indicate kimberlite, no garnet no kimberlite!
My first opinion is that while one of the explanations for the river diamonds has always been, "well the pipes are all weathered away and nothing is left but whats in the drainages. I don`t think this is his interpretation. Here`s why.....
...." The ubiquitous Kamafugite eruptive centers of the Mata Corda have complicated the geological exploration of the project area because their magnetic anomolies are indistinquishable from the true kimberlites.
The number of Mata da Corda vents far exceed the number of true kimberlite and, as a late volcanic phase of the APIP, the Mata da Corda PROBABLY COVERS MANY OF THE TRUE KIMBERLITES.(my caps)
High interest subcalcic garnets recovered from the Maxime Member are assumed to be derived from true kimberlites and incorporated in the Maxime at surface. The high interest garnets of the Maxime and the alluvial diamonds are probably derived from the same Early Cretaceous Kimberlite source rocks. GARNETS AND DIAMONDS ARE,THEREFORE, CONSIDERED TO BE THE MOST IMPORTANT INDICATORS IN THE PROJECT AREA. Garnets appear to survive limited distances of transport in the secondary (particularly fluvial) environment and their recovery from stream samples may indicate proximity to source.
The redistribution of garnets, other kimberlitic indictors and diamonds on the Early Cretaceous, post-Araedo land surface is not well understood. The distance that garnets move from their original source kimberlite is dependent on the mode of distribution (fluvial or aeolian) and the prevailing climatic conditions, the abundance of garnets in the Maxime may be used as an indicator of proximity to source, therefore the relatively abundant high interest garnets in the x162,x408,x410 and x348 region may indicate proximity to a kimberlite source. This area has been selected as a target for high-resolution geophysics to be carried out as part of the 2001 exploration program.".....
My comments: the source diamonds are to be found in true kimberlite. Garnets indicate nearby source of true kimberlite. True kimberlite (diamondiferous) placement preceeded the barren Kamafugite placement. tHE barren kamafugite blew through some of the true kimberlite placement taking with it some diamonds. This could result in the kamafugite appearing to be diamondiferous and the source of the river diamonds. This has been the major problem of why limited occasional diamonds are found in these kamafugite pipes. The rich diamond bearing kimberlite is intact below the kamafugite waiting to be discovered????
If we accept his "idea" then the following comments by Read become much clearer.
......."Petrography confirms that X270 is a true kimberlite as opposed to the ubiquitous alkali volcanics of the Mata da Corda. Examination of unnumbered drill core from x270 suggests that the kimberlite and Mata da Corda have HAVE CLOSE SPATIAL RELATIONSHIPS. (my caps) One core sample is Mata da Corda and the other is kimberlite.
IT IS IMPORTANT THAT THE FIELD RELATIONS OF THE X270 KIMBERLITE AND THE MATA DA CORDA VOLCANICS ARE CAREFULLY DOCUMENTED AND UNDERSTOOD.
THIS IS IMPORTANT INFORMATION FOR THE DEVELOPMENT OF A KIMBERLITE EMPLACEMENT MODEL FOR THIS REGION.
THE DEFINATION OF THE POSITION OF THE TRUE KIMBERLITE IN THE LOCAL STRATIGRAPHY IS THE KEY TO THE DISCOVERY OF THE KIMBERLITE THAT CARRYS THE DIAMONDS FOUND IN THE RIVERS."(my caps)........
my Comments: there is the basis of the "new model" determining the depth of the layer of diamondiferous true kimberlite! Could , after determining at what level to focus on, air and ground geophysics help to determine size/ depth to proceed directly to drill testing these areas/levels?
The kamafugite above is never going to produce diamond counts they need and want. Would you agree with the basics of my interpretation of how Rory and George view the way the project mystery should be attacked and resolved?
One other comment from the report should have interest not only to CNB but others as well, BSW comes to mind.
........."Significant portions of the Rio Abaete, Borrachudo,Tirios and Indaia are essentially parallel and this parallelian appears to be structurally controlled. All these rivers are known to carry diamonds.
It has been suggested that the diamondiferous kimberlite may have utilized the same fault system on their route through the crust to surface. These rivers (particularly Rio Abaete) are considered exploration targets due to the structural control and the simultaneous occurrence of garnet and diamonds. A PORTION OF THE RIO ABAETED HAS BEEN SELECTED AS A TARGET FOR HIGH-RESOLUTION GEOPHYSICS TO BE CARRIED OUT AS PART OF THE 2001 EXPLORATION PROGRAM".....
(my caps)
My comment: geez wouldn`t that be somethin, the kimberlite is like a dike running in a fault under the river flat, or individual pipes that have erupted along the faults. Hey, maybe they are still under there and the diamonds found to date are blow off from a kamafugite that came through secondary bringing some of the kimberlite diamonds with it!.
No wonder George wants to go back, must drift off to sleep every night with that on his mind. He knows what he wants to do, money at the "right" price to proceed is what he/we need! |
