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Independent review highlights high-priority basal sulphide targets at Munni Munni
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Soil geochemistry lights up discrete copper anomalies along the ultramafic base
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Co-funded FLEM survey set to finalise targets ahead of potential drilling
Special report: GreenTech Metals has focused its exploration model at Munni Munni, with an independent geochemical review zeroing in on high-priority magmatic sulphide targets at the base of the intrusion.
Specialist geochemist Dr Scott Halley’s review gives GreenTech a clearer framework to assess the largely untested lower reaches of the Munni Munni intrusive complex.
The review identified discrete copper anomalies in soil geochemistry around the basal contact, pointing to potential copper-nickel-PGE sulphide accumulations from early magmatic activity.
The main targets sit deeper beneath the Ferguson Lode at the base of the ultramafic sequence, an area with minimal previous exploration.
GreenTech Metals (ASX:GRE) says the work has identified several high-priority basal targets and a separate 5km by 2km copper anomaly.
The review also found depleted copper in the lower ultramafic section, suggesting copper and other metals were stripped from the magma into sulphide melt – a key step in forming stronger-grade deposits.
Halley said the Ferguson Lode’s position was important in the context of other major PGE systems.
“The lower half of the Munni Munni intrusion is dominated by ultramafic mineral cumulates and has a sharp transition to plagioclase-rich gabbro in the upper half,” he said.
“The position of the Ferguson Lode is just below the boundary with the plagioclase-rich rocks.
“This location within layered intrusive complexes is typical of magmatic PGE systems, including the Merensky Reef in the Bushveld Complex.”
Basal focus
GreenTech says copper anomalism at the base of the ultramafic sequence has elevated the basal contact as a priority target for copper-nickel-PGE mineralisation.
The depleted copper signature matches the segregation of magmatic sulphides and possible build-up of denser sulphide melt near the intrusion floor.
In short, the system may have gone through the sulphide-separation process needed to concentrate copper, nickel and PGEs into higher-grade zones.
“The ultramafic rocks in the lower part of the intrusion have an unusually low copper content strongly suggesting that these magmas at some point contained immiscible droplets of sulphide melt,” Halley said.
“There are several discrete copper anomalies in soil geochemistry around the base of the intrusion which are high priority exploration targets based on this conceptual model.”
Intrusion mapped
The review combined drill-core geochemistry and geological logging to refine Munni Munni’s internal architecture.
Lower ultramafic rocks like peridotite and pyroxenite grade upward into mafic rocks including gabbro, gabbronorite and leucogabbro.
Major and trace-element analysis shows the intrusion formed through progressive fractional crystallisation from a broadly komatiitic basalt parental magma.
GreenTech says the framework is broadly analogous to the Bushveld Layered Intrusive Complex.
The Ferguson PGE Lode sits near the top of the pyroxene cumulates, just below the transition into plagioclase-rich gabbroic rocks, a setting the company compares with the Merensky Reef.
Copper corridor
The review also highlighted a copper anomaly about 5km by 2km in the southern part of the intrusion.
It is associated with elevated titanium and vanadium in a strongly magnetic area, pointing to a possible link with magnetite-bearing gabbroic rocks.
GreenTech says the feature could reflect magnetite-rich zones carrying disseminated magmatic copper sulphides, opening another area for follow-up exploration.
Mapping and rock-chip sampling will aim to define the source of the anomaly.
Survey next
GreenTech will complete a co-funded fixed-loop electromagnetic survey over the priority targets this month.
The FLEM program is designed to detect conductive sulphide bodies beneath the soil anomalies and help rank targets ahead of drilling.
Results will be integrated with the geochemical interpretation to finalise drill targets at the basal contact.
Geology adviser Dr Kevin Frost said the review had broadened the company’s understanding of Munni Munni’s metal potential.
“These new results highlight the prospectivity of the basal contact position, which has not been the focus of previous exploration,” he said.
“And the strong copper anomalism associated with magnetite-rich domains opens up a new area for follow-up exploration.”
Pilbara platform
Munni Munni is one of Australia’s most significant PGE layered mafic intrusions and forms part of GreenTech’s broader West Pilbara critical minerals and precious metals portfolio.
GreenTech has consolidated more than 500km2 of tenure in the district, covering Munni Munni and the nearby Whundo copper-zinc-gold project.
The company sees these assets as the foundation of a multi-commodity critical minerals hub, with the FLEM survey the next step in testing Munni Munni’s deeper sulphide potential.
This article was developed in collaboration with GreenTech Metals, a Stockhead advertiser at the time of publishing.
This article does not constitute financial product advice. You should consider obtaining independent advice before making any financial decisions.
