Image Gallery:
"Modeling Arsenic Geochemistry"

Bernhard Hochwimmer, Executive Director & Manager Geology, Dart Mining NL (ASX code: DTM) submits this image using Surfer for modeling arsenic geochemistry.

Contoured arsenic analyses in ppm As from approximately 2.9 x 2.0 km DMM grid, initially comprising 946 soil, float and rock chip sampling (2008) on a 100m x 100m grid with rocks generally 50% less than soils. A 2009 infill program in the 'northern ringlet' and small west and east metalliferous area was sampled on a 25m to 50m x 50m infill comprising 231 rock chip and 210 soil samples. White areas have null results. Peak analyses were used in cases of both soil and rock from a single location. Background is generally 0.5 to 10 ppm As, the Northern Ringlet almost covered with a higher background up to 30 ppm As. Here a flat ENE trending arsenic ringlet is defined by ~ >30 ppm As, peaking at 582750mE, 5972400mN with 1,575 ppm As. This area is coincident with other metal of high tenure within the northern RVD2 drill design zone. From here a string of high ENE trending centers > 200 ppm occur between 59724mN and 59726mN. Arsenic is otherwise widespread with strong NE and NW conjugate trends as both part of the main metal ring about Mt Morgan intrusive complex. Arsenic also appears to form a distal out ring of sporadic high values >70 ppm As, somewhat similar to zinc's distal distribution, enveloping molybdenum, and a broad zone 40 to 70 ppm As exists in the east and south Gentle Annie sector. 

Perhaps leakage from the postulated Gentle Annie intrusives stock occurs from depth since zinc forms a core to arsenic here (zinc can be bimodal distal and proximal in porphyry) whilst zinc is otherwise very distal about Morgan's intrusive complex. In the Northern Ringlet the more NE trending gold and tellurium septum traversing the ringlet is indistinct, arsenic following more closely a flatter common boundary between the Northern Ringlet and metal ring about Morgan's main intrusive complex. An inner zone of arsenical centers also occurs. The gold and tellurium maps show sigmoid features and discuss implications of these and the NE-ENE trends in relation to trans-tensional structures between the Northern Ringlet and larger southern metal ring in terms of higher metal tenure. The causative body to explain the Northern Ringlet’s metal geometry is postulated to be differentiated intrusive porphyry. It would appear the mass Morgan intrusive complex geometry is bilobate to account for both the Northern Ringlet and high metal tenure septum zone that forms the common boundary between the metal rings. Both proximal and distal arsenic appears directly to relate with fluid emanations from the bilobate intrusive. The NE gold & tellurium septum trend considered reflecting sigmoid trans-tension structural control between the lobes and to bisect the Northern Ringlet is more coincidental in terms of arsenic distribution. Rather, arsenic highs follow a flatter ENE septum more closely following the common metal zone between the Northern Ringlet and larger though less endowed metal ring about the outcropping south lobe comprising Morgan's main intrusive complex. As far as can be determined from a limited CSAMT telluric geophysical survey, depth conductors follow the flatter arsenic trend in depth in the central conjoined ring sector. This assessment may change with additional CSAMT work. Data was interpolated and smoothed to an approximate 25 m grid utilizing linear point Kriging. Bernhard Hochwimmer, June 2009.

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