Salvador 1 Update
2008年9月5日 - 3:01PM
RNSを含む英国規制内ニュース (英語)
Salvador 1 Update
BRAZILIAN DIAMONDS LIMITED
Salvador 1 Project Update
Highlights:
* Salvador 1 kimberlite confirmed diamondiferous with
recovery of 12.44 carats from 603.5 tonnes in Pit 1
* Possibly enriched foliated phases yielded 10.44 carats from
preliminary processing of 402 tonnes of kimberlite, as well as
higher microdiamond counts, and are being further examined now at
the Company's mineral processing laboratory in Patos de Minas,
Brazil
* Overlying shallow alluvial deposits enriched compared to
kimberlite
Brazilian Diamonds Limited ("Brazilian Diamonds" or "the Company")
reports that field operations are now completed at its pit sample
evaluation of the Salvador 1 kimberlite pipe in central Bahia State,
Brazil. The Company excavated three pits from 8 to 11m deep, and
processed the extracted kimberlite in a plant built on-site. In
addition, the Company completed three drill holes and conducted
microdiamond tests to identify potentially higher grade zones.
Kimberlite weighing 603.5 tonnes yielded 12.44 carats of diamonds
from Pit 1, demonstrating that the pipe is diamondiferous, although
with a low abundance in the portion tested. Preliminary results from
402 tonnes of kimberlite extracted from Pit 3 returned 10.44 carats
of diamonds. Additional kimberlite, mostly from the second and third
pits has been shipped to the Company's mineral processing laboratory
in Patos de Minas, Brazil, for final diamond processing and quality
control tests following initial processing steps on-site.
The pipe is overlain by alluvial sands and gravels from 0 to 10m
thick that have been mined historically for diamonds, and the
underlying kimberlite has been postulated as the source for some or
most of those diamonds. The evaluation program confirmed that the
Salvador 1 kimberlite has significant areal extent of more than six
hectares at the surface, and established that it extends vertically
in a pipe-like shape to more than 200m depth. Mapping, logging of
drill core, and examination of pit walls demonstrated that the
kimberlite contains both strongly foliated and non-foliated rock
units (or "phases"), suggesting multiple ages of emplacement.
Caustic Microdiamond Results
The occurrence of strongly foliated and non-foliated phases within
the Salvador 1 kimberlite suggests the possibility that intrusion
occurred in two events widely separated in time. The older event
would have been before regional metamorphism, which leads to
foliation, and the younger event would have intruded after
metamorphism, simply exploiting the same emplacement structures.
Such widely separated intrusive events might be expected to carry
very different mantle samples, including diamond content.
Microdiamond tests were completed to determine whether strongly
foliated phases carry a different abundance of diamonds than the
non-foliated phases. Samples were processed by SGS-Geosol using
their new laboratory in Brasilia. The process began by
disaggregation of each sample at the Company's Patos de Minas
laboratory, under the direction of a representative of SGS-Geosol.
This disaggregation stage used a 0.075mm screen, with all material
finer than that being discarded. The reduced samples were then
transported to SGS-Geosol's Brasilia laboratory for caustic fusion,
again using a 0.075mm bottom sized screen.
A total of 768kg of kimberlite were treated for microdiamonds with
half being from the strongly foliated phases. A total of 28
microdiamonds remaining on a 0.075mm screen were recovered, with 90%
(25 of 28) being recovered from the strongly foliated phases (Table
1), which comprised 448kg of sample weight.
Table 1: Results of microdiamond tests comparing non-foliated phases
in Pit 1 to the strongly foliated phases in Pits 2 and 3.
+-------------------------------------------------------------------+
| Square Mesh | Caustic | Caustic Sample | All sample |
| screen | Foliated | Non-foliated totals | totals |
| openings | Sample totals | | |
|---------------+----------------+---------------------+------------|
| | | | |
|---------------+----------------+---------------------+------------|
| | Pit 1, 2 and 3 | Pit 1 | Pit 1, 2 |
| | | | and 3 |
|---------------+----------------+---------------------+------------|
| | | | |
|---------------+----------------+---------------------+------------|
| Sample # | | | |
|---------------+----------------+---------------------+------------|
| Start weight | 448 | 320 | 768 |
| kg | | | |
|---------------+----------------+---------------------+------------|
| 0.600 mm | 1 | 0 | 1 |
|---------------+----------------+---------------------+------------|
| 0.425 mm | 1 | 0 | 1 |
|---------------+----------------+---------------------+------------|
| 0.300 mm | 3 | 0 | 3 |
|---------------+----------------+---------------------+------------|
| 0.212 mm | 6 | 0 | 6 |
|---------------+----------------+---------------------+------------|
| 0.150 mm | 3 | 3 | 6 |
|---------------+----------------+---------------------+------------|
| 0.105 mm | 4 | 0 | 4 |
|---------------+----------------+---------------------+------------|
| 0.075 mm | 12 | 0 | 12 |
|---------------+----------------+---------------------+------------|
|
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