Geological Survey of Tanzania (GST) and Ministry of Energy and Minerals of Tanzania have organized the Workshop “Launching High Resolution Airborne Geophysical Data at Julius Nyerera Convention Center (17 January, 2014, Dar es Salaam, Tanzania). Around 150 delegates have attended the workshop from government and private sectors.
Geotech Ltd. and Sander Geophysics have finished the airborne magnetic, gravity, electromagnetic (VTEM), radiometric surveys in 31 districts and presented some results of the surveys.
Permanent Secretary (PS) of Ministry of Energy and Minerals Mr.Eliakim Maswi said – the surveys were carried out under the Sustainable Management of Mineral Resources Project, saying the purpose of the survey was to identify potential zones of mineralization. “The main objective of the project is to improve the socioeconomic impacts of mining for Tanzania and Tanzanians and therefore enhance local and foreign investments”, said PS.
GST Chief Executive Officer , Prof. Abdulkarim Mruma said: “geophysical data acquired through the high resolution airborne geophysical surveys allow fast and accurate delineation of mineralised targets and when augmented with geological and geochemical datasets are highly effective in attracting new exploration ventures.” Prof. Mruma noted that the availability of the modern geo-scientific data will stimulate investments into mineral and other sectors and will improve the effectiveness of exploration programs.
Saturn Minerals Inc. — announces that it has completed approximately 4,540 line-kms of airborne gravity survey over the Company’s coal and oil properties in eastern Saskatchewan & western Manitoba. The helicopter-based survey (the “Sander Survey”) (see Saturn News Release, June 14th, 2011) was conducted by Sander Geophysics Ltd. of Ottawa, Ontario, over the Armit, Muskeg, Overflowing, Rat Creek, Turnberry, Mistatim and Red Earth coal properties, and over the Little Swan and Bannock Creek oil properties (see attached map). The Sander survey was flown with narrowly-spaced lines (120-150 metres) and was designed to add a significant amount of geophysical gravity and magnetic data, and interpretation to the Saturn Exploration Model for eastern Saskatchewan & western Manitoba concerning potential accumulations of coal, hydrocarbons and other minerals. The final results of the survey are expected to be delivered by the end of August.
Final results from the gravity and magnetic survey that SGL flew for Saturn Minerals in June, over their properties in eastern Saskatchewan and western Manitoba, will soon be available. The helicopter survey was flown with tight line spacing (120-150 metres) permitting enhanced modeling of the potential accumulations for coal, hydrocarbons and other minerals.
Drill targets of the summer program were selected based on the Saturn Exploration Model with the objective of verifying & testing a spectrum of certain geophysical signatures to establish stratigraphic correlation between coal-bearing drill holes over a wide area and the potential presence of a large-scale structural control favorable to coal accumulation. The summer program will be the third exploratory drill campaign for coal conducted on the Saskatoba Project and is expected to provide the requisite data for a more encompassing drill campaign which will be designed to establish coal reserves from Saturn’s known coal discoveries and larger-scale coal targets.
“This will be the third highly-focused drill campaign on the Saskatoba Project” stated Stan Szary, President & CEO of Saturn. “Like the previous two campaigns before it which were successful in discovering the Leif and Karolina Coal Basins, this program will help us assess the potential of various geophysical targets and provide the basis for a larger-scale area-wide effort to ascertain ultimate resource potential on Saturn’s lands.”
Base Metal Targets
The exploration and drill targets for base metals, shown in Figure 1, were prepared from analysis and modelling of the recently completed gravity, electromagnetic and magnetic surveys flown over a large portion of its properties near Paulatuk, NT. The analysis was prepared in conjunction with mapped geology, topography, satellite imagery and previously acquired airborne and ground geophysical data.
The following provides a summary of the 41 separate base metal exploration targets selected as a result of the analysis and modelling:
Gravity (22 targets) 76 km2; Magnetic (7 targets) 108 km2; Electromagnetic (12 targets) 54 km2.
The methods indicate the data type where the target is most evident, although many targets incorporate coincident or complementary geophysical responses from at least two data types. The base metals targets are broken into several categories, depending on the nature of their responses and their estimated depths. Nine of these targets are designated for assessment by geological prospecting and sampling as they may outcrop.
Location map showing the 41 base metals targets on the 100%-owned properties of Darnley Bay Resources Limited. The red dashed outlines indicate the two areas of highest priority for follow-up.
3D Gravity Modelling
Geoscientists study the earth’s gravity field to determine the density of the rocks in the subsurface. Changes in density from surface to tens of kilometers in depth affect the gravity field that we measure. The more basic (mafic) classes of igneous and metamorphic rocks, and most metallic minerals, have higher densities and produce stronger gravity responses. The 132 mGal Darnley Bay gravity anomaly is perhaps the strongest of its kind in the world, reflecting an isolated intrusion.
In 2007, Darnley Bay contracted Mira Geoscience
, through its Vancouver office, to apply 3D modelling to the ground gravity and airborne magnetic data
available over the Darnley Bay anomaly and surrounding region. A 3D model of a large, deep-seated mafic/ultramafic intrusion was developed to explain the anomaly on a regional scale. The effect of this model was subtracted from the gravity and a more detailed model of the upper 10 km of the earth’s crust was prepared from the residual gravity field, to ascertain the shape of the anomaly source at depths of economic interest. The modelling in 2007 resulted in the reassessment of the geological models to explain the anomaly source and its mineral potential. Darnley Bay realized that it required gravity data in much greater detail before embarking on a drill program.
Northtech Drilling Ltd. commenced drilling Darnley Bay’s first 2010 base metals target on August 28.
Target EM-8 is currently being drilled, an electromagnetic anomaly with coincident magnetic response interpreted from the 2010 VTEM survey (see target map on the home page at www.darnleybay.com). It will be followed by target M-7, a magnetic anomaly with coincident electromagnetic response. Both drill holes are at 65° from the horizontal with a length of 300 m. Concurrently, other targets are being followed up on the ground with gravity and magnetic surveys, and geological prospecting, to prioritize targets for the continuing drill program.
The airborne gravity survey
) completed in April 2010 confirmed the size, shape and amplitude of the Darnley Bay anomaly and greatly improved the resolution and detail. Mira Geoscience
was once again contracted to prepare a 3D model. Mira utilized the same regional model for the intrusive body and prepared a new model of the upper 10 km of the earth’s crust from the airborne survey’s residual gravity field. It utilized the free-air gravity field and incorporated a correction for the surface topography. Since the surface rocks incorporate a range of gravels and sediments with different densities, their effects cannot be fully corrected for and as a result, some topography is visible in the model.
1. Preparing a representation of the earth as a volume measuring 63.5 km E-W by 66.0 km N-S by 10.25 km vertically. The cells within the volume measure 500 m x 500 m x 250 m.
2. Implementing geological constraints, incorporating the sediments mapped on surface and their densities, and the log of Darnley Bay’s 2000 drillhole.
3. Applying the GRAV3D inversion, which determines a geologically reasonable density to each cell in the model while best-fitting the observed gravity data. This process takes several days of continuous iteration on a massively parallel computer.
The result is a 3D volume model where the density varies between each cell. For display purposes, a series of density surfaces are extracted from the model to better appreciate the geometry and concentrations of higher density material.
DISCOVERY OF THREE KIMBERLITE PIPES
Darnley Bay Resources Limited and Diadem Resources Ltd. announce that they have completed the first phase of 2010 drilling on their 50/50 joint venture package of 33 claims on the Parry Peninsula, Northwest Territories. Of the four targets drilled, three have resulted in the discovery of new kimberlite pipes. These are in addition to the ten kimberlite pipes discovered in 2000, of which six have proven diamondiferous. The kimberlite material intersected in the 2010 drilling is being prepared for shipping to CF Mineral Research Ltd. in Kelowna BC for analysis.
Darnley Bay and Diadem are quite encouraged by the initial success of the drill program. Numerous high priority targets remain untested. The results of this first phase are being incorporated in planning for the second phase of 2010 drilling, as well as determining the targets that are better suited for drilling from frozen lakes in February-April 2011. Diadem is funding the 2010 program.
This hole targeted a 1.7 ha ground magnetic low of 10 nT amplitude, partially covered by a lake. It intersected 15.35 m of kimberlite, hosted in dolomite. The kimberlite intersection is described as “Dark green to black, fine grained matrix consisting of dark green ferro-magnesian minerals and 10 to 35% green partially altered olivine and peridotite fragments, some being completely talc altered. Contains numerous greenish, subrounded possible mantle derived fragments to 100 mm.”
This hole targeted a 3.6 ha ground magnetic low of 325 nT amplitude, partially covered by a lake. It intersected 7.6 m of kimberlite, hosted in dolomite. The kimberlite intersection is described as “Dark gray to blackish-green, massive, fine to medium grained kimberlite (micro breccia). The mass of the kimberlite comprises dark green 1-5 mm mafics in a white clay – calcite matrix.”
This hole targeted a 10.2 ha ground magnetic low of 105 nT amplitude, partially covered by a lake. It intersected 0.6 m of kimberlite, hosted in dolomite. The kimberlite intersection is described as “Dark gray to black, loose packed, sub-rounded to sub-angular wall rock and some mantle derived fragments in a fine to medium grained matrix. Fragments consist of 1 to 25 mm black mudstone and chert, gray dolomite and some greenish-gray, rarely apple green, serpentinised mantle-derived xenoliths.”
Darnley Bay Resources releases preliminary results from the recently completed Geotech VTEM and Sander AirGRAV surveys over a large portion of its properties near Paulatuk, NT. Darnley, with the assistance of Paterson, Grant & Watson Limited, consulting geophysicists of Toronto, Canada, has prepared a series of images and commentary from the field data, which will be downloaded from the Company’s website under the “Current Activities” heading on the home page (www.darnleybay.com) by the end of April. We stress that this material was prepared from the field data. The final data will have several standard processes applied by the contractors to make corrections, improve data resolution and remove topographic effects, level errors and noise. From these final data, 2D and 3D models will be prepared, and drill targets located and prioritized.
About the exploration of Paulatuk gravity anomaly: http://explorationgeophysics.info/?s=darnley
Darnley Bay Resources has outlined its 2010 exploration plans for its properties in the Paulatuk NT area. It has completed permitting for airborne surveys to take place in March-April 2010.
is preparing to mobilize to Paulatuk for a 5,980 line-km airborne gravity and magnetic
survey covering all of the Darnley’s Bay properties where they encompass the Darnley Bay Gravity Anomaly. The purpose of the survey is to significantly improve the resolution of the previous ground gravity surveys over the Anomaly and to locate targets for drilling.
. is preparing to mobilize to Paulatuk for a 2,600 line-km airborne VTEM
time-domain electromagnetic and magnetic
survey covering all of the eastern and northeastern portion of the Company’s properties, where previous sampling and airborne surveys indicate the presence of gabbro sills and dykes.
outline its 2010 exploration plans for its properties in the Paulatuk NT area. It has completed permitting for airborne surveys to take place in March-April 2010.
Paulatuk gravity anomaly: The Geological Survey of Canada (GSC) conducted a regional gravity survey in 1969 as part of its national gravity coverage providing readings at 2.5 km (1.55 miles) to 20 km (12.4 miles) intervals over and surrounding the area of Paulatuk; it discovered the gravity anomaly. In 1970 the Dominion Observatory published the Inuvik-Horton River map sheet. Northgate Exploration Limited flew a helicopter-borne magnetic survey over the most intensive part of the gravity anomaly and detected a coincident magnetic anomaly. A number of seismic profiles were surveyed in the early 1970’s on the western portion of the AMI, most of these are located on the western sedimentary platform. They identified a deep 6-800 metres trough (NW) along the west margin of the dyke swarm, the significance of which is still unknown. The GSC undertook an aeromagnetic survey over the positive gravity anomaly. The survey was flown along north-south oriented flight lines spaced 2 km apart, at a constant height of 610 metres (2,000 feet) above sea level. It defined the positive magnetic anomaly (detected by Northgate in 1970) at 1200 nT amplitude, coincident with the gravity anomaly. The GSC collected samples from a number of basic sills east of the anomaly that contained minor amounts of nickel, copper, platinum, gold, silver and cobalt. These rocks and metallics may be genetically associated with the anomaly. The GSC suggests that the cause of the anomaly (130mGal) may be an igneous intrusive similar to that in the Sudbury Basin, Ontario (30 mGals), Norilsk in Russia (25 mGals), and the Bushveld Complex in South Africa (65 mGals). Ref: GSC Open File Report 2789. The DBR 1997 aeromagnetic survey indicated that the main intrusive has 4 upward extending feeder pipes. The feeder pipes give way to 9 laterally trending shallow magnetic zones, which are referred to as “offshoots” being drill targets for mineral deposits. The aeromagnetic survey in the central portion of the Anomaly, revealed a number of kimberlite targets. These targets could have conveyed diamonds and also fragments of sulphide mineralization to the surface revealing the composition of the Anomaly and the possible presence of Ni, Cu, PGE. DBR carried out ground geophysical surveys on the Thrasher Zone, which revealed 5 electromagnetic conductors within 250 metres of the surface that have coincident gravity and magnetic responses, 3 of the conductors are horizontal and 2 are vertical. The 2 vertical conductors are along fault structures that represent conductive shear zones and possible associated mineralization. They have strike lengths of 1,500 metres, widths of 450-800 metres and are centered 250 metres below surface. (Source http://www.darnleybay.com)
QUEST-South Project in British Columbia includes a new airborne gravity survey (Sander Geophysics) which covers 45,000 square kilometers between Williams Lake and the USA border. The airborne gravity digital data, grids and final technical report can be downloaded at Geoscience BC QUEST Project Data Releases. This gravity survey involved more than 25,000 line kilometeres of data at a 2 km line spacing.
The QUEST-South Project is focused on the Quesnel Terrane, south of Williams Lake, and will provide new geoscience information over an area of 130 000 km2. The QUEST-South airborne gravity survey was under taken by Sander Geophysics using their aiborne inertially referenced gravimeter (AIRGrav). This region of the province has been explored and mined for decades and remains one of the most actively explored and prospective areas for discovery of new Cu, Mo and Au resources in British Columbia.
The Sander Geophysics AIRGrav system developed in Ottawa, Canada was successfully used in the 2008/2009 AGAP field season in East Antarctica. This high resolution data can be collected while flying a constant elevation over the landscape in a technique called ‘drape flying’. ‘Drape flying’ in useful for the laser data collection, but poses difficult challenges for traditional gravity systems that must be carefully stabilized due to their sensitivity to movement. How gravity works for the task you can read here.
December 2009 The 2009 ICE Bridge project over Antarctica has wrapped up successfully. Designed to provide vital information about ice at the poles, ICE Bridge is a NASA project to bridge the gap between the retirement of ICESat I (2009) and the launch of ICESat II (expected in 2014-15). The project used a specially modified NASA DC-8 mounted with various pieces of equipment from multiple agencies, including Sander Geophysics’ AIRGrav system. This season, 21 missions were flown over Antarctica from a base in southern Chile, totalling 155,000 km and 227 flight hours. This exceeded the original plan of a 17 flight mission, with some of those additional flights designed specifically to take advantage of the high resolution and accuracy of Sander Geophysics’ AIRGrav system. Highlights include the acquisition of detailed gravity maps covering the floating ice shelves associated with major West Antarctic outlet glaciers, which is expected to contribute to a better understanding of ice sheet mass balance and its relation to the changes in the polar climate.