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February 14th, 2011
The winter 2011 joint venture (“JV”) exploration program at its 58.8% owned ATW Diamond Property is now underway. The JV is operated by Almaden and all parties have a working interest. The winter 2011 program will comprise the completion of approximately 134 sonic overburden drill holes. The holes will be drilled within a 3 kilometre by 4 kilometre area of interest that lies at the at the “up ice” terminus of a 20 kilometre long kimberlite indicator mineral (KIM) dispersion train.  The dispersion train has been traced “up ice” and easterly under MacKay Lake over several campaigns by Almaden and partners.   The purpose of the 2011 drill program is to define the “up ice” and lateral extent of the head of the KIM dispersion train under Mackay Lake.  Previous sonic drilling campaigns completed during 2003 and 2008 (see Almaden Minerals Ltd. press release: October 22, 2008 +) have defined the southern and “up ice” (eastern) cut-off of the dispersion train, resulting in the definition of the present high priority area if interest.  Based on the results of winter 2011 exploration, targets will be chosen for diamond drill testing during winter 2012.
Read more: February 14th, 2011 news release +

 

The Lac de Gras area diamond project is situated at Mackay Lake in the Northwest Territories, immediately south of the Diavik property and west of the DHK property. 150,000 acres was staked by ATW Resources Ltd. in 1992, which was owned by the following companies: Troymin Resources Corporation (20%) Almaden Resources Corporation (40%) and Williams Creek Explorations Limited (40%).

In 2003 and 2008, sonic drilling was conducted to collect samples of till sediments in the base of Mackay Lake. The drilling was undertaken in a series of north-south fences in the vicinity of previously recovered kimberlitic indicator minerals. The samples from 2003 and 2008 were processed by Vancouver Indicator Processing and the resulting concentrates sorted by KIM Dynamics of North Vancouver, B.C. A total of 7122 potentially kimberlitic indicator minerals were recovered from these samples including numerous garnets and olivines and minor chromite, ilmenite and Cr-Diopside. The mineral recoveries define a mineral dispersion train of approximately 3 km (E-W) by 1.3 km (N-S). The Mackay Lake indicator mineral plume (MKIP) is constrained to the east and south but is open to the north, and possibly also to the west.

In September 2008, Mineral Services Canada Inc. (MSC) was contracted to undertake a study on the results including an assessment of the mineral abundances, a study of the KIM surface textures, and an analysis of a subset of the recovered garnets. A total of 547 potentially kimberlitic garnets were selected by MSC for analysis from 8 of the 71 positive sonic drill samples (see sample location map). In addition, the garnets and ilmenites were examined for the presence of high-interest surface textures. Several samples were found to have garnets with preserved kelyphitic rim fragments suggesting that the grains may be located in close proximity to their kimberlitic source.

Analysis of the garnets confirmed the earlier interpretation that the Mackay Lake Project has peridotitic garnets that include a significant number of high interest harzburgitic (G10) types that are commonly associated with diamond (see Fig X). The study undertaken by MSC also highlighted for the first time the presence in the MKIP of a small population of low-Cr garnets with compositions equivalent to those of eclogitic garnet inclusions in diamond (see Fig X). Another significant finding of the study was the interpretation of possible multiple sources contributing grains to the MKIP.  A high confidence first order observation points to at least 2 distinct sources for garnets recovered in the east-central and western portions of the MKIP, respectively. The western zone is characterized by the absence of harzburgitic G10 garnets and the presence of eclogitic garnets with diamond associated compositions, while the eastern zone is characterized by the presence of significant G10 garnets and paucity of high-interest eclogitic garnets. A lower confidence second order observations suggests that there may be as many as 5 distinct sources contributing to the MKIP. This is based on subtle but potentially significant differences in the composition of garnet populations derived from different sample groupings (e.g. Fig. X through X). Table Y below contains an assessment of the relative diamond potential of the 5 possible sources:

None implies that there are not enough grains present to ascertain the eclogitic diamond potential. Designations of low – moderate – high are relative to each other only. With the data available it is not possible to make quantitative interpretations of the diamond potential.

Almaden are in the process of re-evaluating the historical geophysics covering the MKIP with a view to generating new targets for drilling in the winter of 2009.

 

The property covers the likely source area of a significant indicator mineral train that is known to be at least 20 kilometers long. Past microprobe work on these indicator minerals identified G10 garnets and other minerals that are interpreted to have been derived from at least one kimberlite source that is also interpreted to be at least moderately diamond-bearing (see Almaden's March 22, 2002 news release). Till sampling efforts in the past have narrowed the indicator mineral source area to roughly 1 by 1.5 kilometers in size. This work was also confirmed by abrasion studies carried out on the indicator minerals, indicated a very local source. Last year this reduced area was covered by electromagnetic, magnetic and gravity ground geophysical surveys. These surveys identified several subtle targets within the interpreted indicator mineral source area. A bathymetric survey of the lake bottom in this area has been recommended in order to give better control for the gravity results.

 

Indicator Mineral Chemistry:

A Cr2O3-CaO diagram for kimberlitic garnets recovered in till samples (blue circles) and lake sediment till samples recovered from overburden drill hole 98RC12 (red squares) located within the same indicator mineral train. G9 G10 and low Cr2O3 garnet field boundaries are from Gurney, 1984.* (*Gurney, J.J., 1984. A correlation between garnets and diamonds. In: Glover, J.E., Harris, P.G. (Eds.), Kimberlite occurrence and origins: a Basis for Conceptual Models in Exploration. Geology Department and University Extension, University of Western Australia, Publication 8, 143-166).

 

 

April 9th, 2009:
Almaden announces results of winter drill program at ATW Diamond Property
During winter 2009 exploration at the ATW Diamond Property nine diamond drill holes totaling 694 metres were completed.  The drill holes were designed to test a series of priority magnetic and weak electromagnetic (conductive) geophysical anomalies located at the up-ice terminus of a 20 kilometres long kimberlite indicator mineral (KIM) dispersion train (see Almaden News Release: February 4, 2009).  Drill testing of six (6) isolated magnetic high anomalies resulted in the intersection of weakly magnetic pyrrhotite bearing metamorphosed sedimentary rocks.  The magnetic susceptibility of these rocks was sufficient to explain the observed geophysical signatures.  A single linear magnetic anomaly was also drill tested.  The anomaly was found to correspond with a region of locally thick overburden cover interpreted to contain an increased proportion of magnetic minerals.  The remaining two drill holes tested subtle conductive anomalies and did not intersect kimberlite.

2009 drill testing of geophysical anomalies at the ATW Diamond Property did not locate the kimberlite source(s) of a compelling KIM dispersion train.  The dispersion train has been traced “up ice” and easterly under MacKay Lake over several campaigns by Almaden and partners.  Future exploration will include an examination of KIM grain morphology and the completion of additional sonic overburden drilling, gravity geophysical and bathymetric surveys if warranted, in an effort to further refine the “up ice” terminus of the KIM dispersion train and locate the KIM source or sources. [read more +]

March 2nd, 2009: a quick progress report from the field.  The APEX crew arrived at the camp on Saturday afternoon, and everything is in order. Camp construction will be completed this afternoon.

Our ground geophysical survey crew is currently on the lake covering the ATW004 and dyke targets today.  Surveys should be complete over the first 5 proposed drill targets prior to arrival of the drill crews.  They can then continue over the remaining outlier targets without being influenced by proximity to drilling equipment.

The collar location for the 1st drill hole (anomaly ATW004) will be finalized in early next week, with finalization of a further 4 collars in the following few days. Barring any unforeseen complications, drilling should commence by March 6th. See photographs from ATW on Almaden's BLOG +

February 4th, 2009: Almaden has received the results of a comprehensive reinterpretation of past magnetic, electromagnetic/resistivity and gravity survey data.  The reinterpretation was undertaken by Petra Geophysical Consulting Inc. (Petra) on geophysical surveys previously completed at Almaden’s 58.8% owned ATW diamond property located at Mackay Lake, NWT. Petra’s analysis in conjunction with the Spring 2008 sonic drilling results forms part of a recent reinterpretation of extensive geophysical and geochemical data that has identified numerous high-quality targets.  Drill testing is planned for at least seven of these targets during the coming months. [read more +]

October 22nd, 2008: Almaden has received results from a Mineral Composition and Surface Texture Study conducted by Mineral Services Canada Inc. (MSC) on mineral grains recovered in 2003 and 2008 on the ATW diamond property. MSC’s analysis suggests that there could be as many as five distinct kimberlite sources contributing minerals to the Mackay Lake indicator mineral train. The mineral abundance and composition and surface texture data further suggest that these sources may lie within the currently defined mineral train, which extends over an area of approximately 3.5 kilometres by 1.5 kilometres. Three of these sources show the potential to contain diamonds of peridotitic or eclogitic origin. The identification of rare eclogitic garnets with diamond association compositions in this work is encouraging as diamondiferous eclogite can be a significant contributor to the economic potential of kimberlites. [read more +]

March 2004 : A magnetic and electromagnetic geophysics program was completed in December 2003 and several subtle anomalies were identified. No drilling is contemplated this winter.

April 2003 : A till sampling program has been completed on the ATW property. Seventy-seven holes were drilled to recover samples of basal till in order to determine the source of a 20 kilometre long kimberlitic indicator mineral train in glacial till. This train had previously been traced easterly and up ice to within five kilometres from a fence of holes which did not encounter indicator minerals, outlining a source area for the kimberlitic body. This source area was tested by the current drill program. Picking and identification of indicator minerals from the samples is still not complete.

April 2002 : The drilling program is completed and no kimberlite was found. Further work is being planned for the property which may include sonic drilling and geophysics. Please see press release April 4th 2002.

March 1999 : The Company staked an additional 7 claims totalling 15,495 acres to further cover the area in the direction up-ice from the indicator mineral train.  These claims were transferred to Kennecott to be part of the ATW agreement and Kennecott reimbursed all staking costs. Under the period of option to Kennecott the area of this indicator mineral train was never flown for airborne geophysics.