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Gold Prospect in Lake Lefroy
Lefroy Exploration Limited (ASX: LEX) ("Lefroy" or "the Company") is pleased to advise that Gold
Fields Limited (NYSE: GFI) ("Gold Fields") has provided the fourth export of validated drill results from a major aircore (AC) drilling program on the Company's tenements over Lake Lefroy (Figure 1). The program commenced in late January 2019 and is part of the $25million Farm-In and Joint Venture (JV) agreement between Lefroy and Gold Fields that commenced in June 2018.
The tenements form part of the Western Lefroy tenement JV package that cover 372km2adjoining the St Ives gold camp (Figure 1). Western Lefroy is part of the wholly owned greater Lefroy Gold Project (LGP) located 50km south east of Kalgoorlie. The Company maintains exploration at the non-JV Eastern Lefroy.
Figure 1 Lefroy Gold Project tenement package highlighting the Gold Fields Farm in &
JV Western Lefroy package, proximity to Gold Fields St Ives and the non-JV eastern
Lefroy Project. Refer to inset for drill program detail.
Gold Fields commenced the major full field aircore (AC) drilling program in late January 2019 (refer: LEX ASX release 31 January 2019). The original program involved completing approximately 350 vertical holes spaced 200m apart on traverses 1km apart to cover most of the tenure in Lake Lefroy using a specialised lake drilling rig (Figure 3). This has been well exceeded and infill drilling is continuing. The program is designed to yield foundation geological and geochemical information that will be interrogated in conjunction with the geophysical data to deliver specific drill targets for deeper drill testing and hence termed foundation drilling. Gold Fields provides monthly validated data exports to the Company.
Since commencement of drilling, 602 vertical air core holes totaling 33,141m have been completed. Assay results have now been received and validated for a total of 520 holes. Results for the initial 421 holes were reported by the Company in ASX releases dated 15 April 2019, 29 May 2019 and 11 June 2019. This announcement refers to results from the additional 100 holes and is dated 28 June 2019.
The AC drilling is a reconnaissance exploration technique, searching for both geochemical anomalies and geology from the bedrock or top of fresh rock (TOFR) beneath the lake surface clays and oxidised rocks that comprise the regolith. The wide spacing of the drill holes is designed to conduct effective first pass reconnaissance to screen large areas. The results from these holes provides geological and geochemical vectors for infill drilling at specific anomalies.
The depth of the regolith and TOFR at Western Lefroy is highly variable, ranging from 6m to 138m vertical and averaging 55m. The variability in the depth to TOFR is also controlled by the distribution and thickness of palaeochannels (ancient river channels) that mask the underlying older bedrock (termed transported cover).
The interface between the palaeochannel material and bedrock can have a variable thickness of pebble gravels and or sand that can be gold mineralised. The tenor of gold in the bearing gravels and sands can be used as a vector to locate the primary source in the bedrock.
The recent results from composite samples (Table 1) have further expanded the footprint and strike of the LLT06 gold prospect identified by the Company during its 2017 lake drilling campaign (Figure 2). The results are predominantly from an infill drill phase with line spacing to a nominal 500m and hole spacings to 100m along strike of earlier anomalous gold results.
Significantly, multiple gold intersections were recorded adjacent to the LLT06 gold prospect that reinforce this as another key gold mineralised regolith anomaly (Figure 3). Significant intersections from the recent program include:
These results further support and expand upon a prior LEX intersection of 4m @2.39g/t Au from 88m in LEFA113, one of the initial 14 holes drilled at LLT06 (refer LEX ASX release 3 April 2017).
Importantly, the high-grade interval (2m @7.29g/t Au) in KD81533 occurs within pyrite altered siltstone (bedrock), that confirms buried primary mineralisation beneath the transported cover at LLT06. This is further supported by the gold intersection in SAL1486, also occurring in bedrock, located approximately 400m to the north of KD81533.
Figure 2 Map highlighting drill holes completed in Lake Lefroy coloured by maximum gold value and the location of Zanex, LLTO6 and Eastern Shoreline, with key gold intersections relative to the Woolibar Fault.
The combined Gold Fields and LEX drill results at LLT06 define a broad regolith hosted gold anomaly that has dimensions of approximately 1200m by 1000m. The drill spacing is 400m between lines and 100m between vertical holes that is considered wide spaced early stage. Results are pending for holes drilled at LLT06 and elsewhere at the southern end of the lake.
The developing gold anomaly at LLT06, combined with the 4km long Zanex trend located approximately 10km to the north west (Figure 2), demonstrates the growing gold prospectivity of this large previously untested are under Lake Lefroy.
Ongoing Work Program
The lake aircore drilling remains in progress and is expected to continue in Q3/19. Monthly validated drill data exports will be provided by Gold Fields with the next information expected at the end of July 2019. Detailed compilation and assessment of all results will be placed in context upon completion of the program.
Compilation and interrogation of recently acquired geophysical data (gravity, magnetics) with the foundation drill data is ongoing and will provide base for advancing the geological interpretation and target generation for deeper drilling.
Figure 3 Specialised lake air core drill rig on Lake Lefroy. Photo taken from the Eastern shore at the southern end of Lake Lefroy looking south to the Parker Hills (Photo by W Johnson)
Background to the Western Lefroy JV
The Western Lefroy tenement package is a Joint Venture with Gold Fields which commenced on 7 June 2018 (ASX: LEX 7 June 2018). Gold Fields can earn up to a 70% interest in the Western Lefroy tenements by spending up to a total of $25million on exploration activities within 6 years of the commencement date. This includes a minimum expenditure requirement of $4 million within 2 years before Gold Fields can elect to withdraw.
Gold Fields is a South African based gold producer with seven operating mines in Australia, Ghana, Peru and South Africa with a total attributable annual gold-equivalent production of 2.2million ounces. Mining assets in Australia include a 100% interest in St Ives, Agnew and Granny Smith in the Eastern Goldfields of Western Australia with a combined annual production of 935koz. Gold Fields also has a 50% interest in the Gruyere Project with Gold Road Resources (ASX: GOR) also in the Eastern Goldfields.
Gold Fields commenced exploration on Western Lefroy in July 2018 involving multi-disciplinary ground and airborne geophysical surveys (gravity and magnetics) primarily located on or near Lake Lefroy. This extensive detailed magnetic survey program is complete. These surveys will build upon the data collected by the Company in 2017 and deliver a foundation detailed geophysical dataset to be used for target identification and focused RC and diamond drilling.
To complement this foundation geophysical data, Gold fields commenced a large full field aircore drill program on Lake Lefroy within the Western Lefroy JV tenements in late January 2019.