A high resolution ground gravity survey was conducted at West End and Investigators, recording multiple gravity peaks and strong targets for the potential discovery of further nickel-copper sulphide mineralization.
() (FRA: S0G) used recent geophysical surveys to identify several new nickel-copper sulfide targets on its flagship high-grade Mt Alexander project in the gold fields of northeast WA.
Ground-based electromagnetic surveys along the cathedral belt identified shallow electromagnetic conductors similar to those that led to nickel-copper sulfide discoveries at Stricklands, Investigators, Cathedrals, and Radar.
However, ground-based electromagnetic surveys were of limited effectiveness in the West End due to the conductive coverage west of investigators.
Subsequently, a high resolution ground gravity survey was conducted over West End and investigators with data supporting the prospectivity of the area for nickel-copper sulphides.
“Targeting nickel-copper sulphides”
Several targets have been identified by electromagnetic downhole (DHEM) surveys, with three strong EM conductors on the hole identified from MAD199 at Investigators that support the potential for extension of the thick high grade mineralization.
St George’s Executive Chairman John Prineas said: “The results of the gravity survey are very exciting and could provide a big step forward in targeting nickel-copper sulphides in the cathedral belt.
“A number of gravity features are compelling drill targets for massive sulphides.
“These gravity peaks are located within the interpreted trend of the mineralized intrusive host unit, an ideal location for dense massive sulphides.
“The simultaneous use of downhole EM and drilling continues to provide a vector for mineralization at depth. The multiple EM plates modeled around the new high grade MAD199 discovery support the potential for additional high grade mineralization in this zone.
“Drilling is continuing 24/7 and we look forward to reporting further drilling results.”
High priority targets
A number of gravity features have been identified along the mineralized trend by researchers and at West End in areas that have never been drilled – providing targets for the potential discovery of further nickel-copper sulfide mineralization.
Of particular interest is a chain of high gravity peaks, the largest of which appears in the West End.
Many of these features are descending along the interpreted plane of ultramafic intrusives and seen in gravity data as discrete “bull’s-eye” in areas of lower density.
These features are classified as high priority and an additional drilling program to test them is prioritized.
Plan view of West End map and investigators showing recent gravity survey data and previous drilling. Peaks of gravity are targets for potential zones of nickel-copper sulphides.
Continuity of massive sulphides at depth
MAD199 intersected a 10.96 meter thick interval of nickel-copper sulphides from 333.6 meters downhole, which is the deepest massive sulphide occurrence drilled in the cathedral belt to date .
This discovery is an important step in the belt of cathedrals because it confirms the presence of massive nickel-copper sulphides at depth, beyond the detection limit interpreted by surface EM surveys.
The DHEM survey at MAD199 recorded a strong EM response on the hole between 345 meters to 350 meters downhole with three new modeled EM plates and the DHEM survey at MAD195 also resulted in the modeling of three EM plates – with one of these plates (MAD195_p1) intersected by MAD199.
All EM plates have varying lengths, dip directions, and conductivities, indicating complex geometry at the source of massive sulphides – and the likelihood that there is more than one source.
Progressive drilling was designed to test the extent of DHEM conductors and plunge continuity of the MAD199 mineralization.
The first follow-up hole will target approximately 40 meters northwest of MAD199 – a submerged area of the intrusive host unit and an interpreted mineralized trend.
This new drilling – MAD201 – will start once MAD200 is completed.
New drilling is also planned along the direction from 197 MAD to continue the search for nickel-copper sulphides in this trend.
Additionally, the abnormal EM responses recorded in MAD198 (Stricklands) warrant further exploration.
Looking forward to
In addition to the 2021 diamond drilling program, an additional drilling program is planned to test the new gravity characteristics.
Targets are in areas without prior drilling, requiring preparation of earthworks and access roads prior to drilling and approval of a new work program.
These issues are prioritized so that drilling for these targets can begin as soon as possible.