GRI has applied to Mineral License and Safety Authority (MLSA) for the transfer of ownership of License No.2018/11 to a wholly owned Greenland-based subsidiary, GRI A/S. The purpose for the transfer is to fulfill a legal requirement for conversion of the MEL to an Exploitation Licence. At the time of writing, the transfer request was awaiting approval from MLSA.
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Summary:
Malmbjerg is a porphyry molybdenum Project similar in style and morphology to the Climax Project, in Colorado, USA. Projects of this type are typically large, measuring in the hundreds of millions of tonnes with molybdenite (MoS2) contents typically measuring less than 1% of the rock by weight. Late hydrothermal processes related to the intrusions were responsible for alteration and deposition of molybdenum sulphide mineralization.
The mineralization occurs as a diffuse zone of molybdenite (± accessory tungsten) in fractures and stockworks in both the intrusives and sandstones. Molybdenite occurs as fracture-fillings and disseminations in association with hydrothermal alteration. The Project is broadly dome shaped with an outside diameter of up to 600 m and a height of approximately 150 m.
Host rocks for the Malmbjerg Project comprise Mid-Tertiary alkalic leuco-granite stocks and clastic sedimentary rocks of the Lower Permian Rode Group. The sedimentary rocks are primarily arkosic and conglomeratic sandstones that have been variously hornfelsed. Intrusive rocks consist of four principal phases: perthite granite, quartz porphyry (Arcturus porphyry), porphyritic aplite, and weakly feldspathic quartz porphyry (Schuchert porphyry). In the western cliff face of Høstakken Mountain, the intrusive/sediment contact is plainly visible, forming a broad arch with the Rode Group rocks draped over top.
Contact relationships within the intrusion are complex and are often ambiguous. The perthite granite is the most widespread phase and is believed to be the oldest. The perthite shows gradational contacts with the Arcturus porphyry, which is compositionally similar to the perthite and is discriminated primarily on the basis of texture. The Arcturus porphyry tends to occur at the top and on the northeast side of the intrusion. Its chemical similarity and complexly interlayered relationship to the perthite granite suggest that the Arcturus may just be another phase of the perthite granite. Following the Arcturus porphyry was the aplite, which occurs as both porphyritic and non-porphyritic variants. The final phase is the Schuchert porphyry, which occupies the northern portion of the Project. The Schuchert is observed to crosscut the perthite granite and the aplite. Silicification, noted in the perthite and aplite, is not seen in the Schuchert porphyry, indicating that it post-dates this alteration event.
Post-mineralization basic and trachytic dikes have been mapped and occur within the Project. The basic dikes are quite narrow, usually decimetre-scale, are steeply-dipping and trend in a NE-SW direction. The trachytes occur as two 5 m to 15 m thick subvertical sheets, striking east-northeasterly. Lamprophyre dikes have been noted in the area but have not been identified in the drift mapping or drillhole logs. K-Ar dates for the intrusives place the age of emplacement at around 25 Ma, which is late Oligocene.
Molybdenite occurs as fracture-fillings and disseminations in association with hydrothermal alteration. The Project is broadly dome shaped with an outside diameter of up to 600 m and a height of approximately 150 m. Accessory pyrite occurs as a halo around the molybdenite zone. Other accessory minerals include minor amounts of wolframite, scheelite, and fluorite. Re-assays done in 2021 confirmed ICP results having below DL (<10 ppm) uranium. There is also very minor galena, sphalerite, and chalcopyrite occur in veinlets at the periphery of the Project.
MoS2 grades tend to level off at approximately 0.35% in the central high-grade core, although local grades of over 1% have been observed. The grades gradually taper off to ppm range with distance outwards and downwards. The mineralization continues up into the sedimentary rocks in the roof of the Project, but the grades are observed to diminish more rapidly than in the intrusives.
Alteration at Malmbjerg occurs as concentric zones of assemblages typical of many porphyry deposits. The innermost zone consists of a silicified zone, which is surrounded by a halo of sericite-K-feldspar alteration, and finally a biotite-magnetite-quartz zone. Extending for up to 500 m from the Project is a large zone of pyrite mineralization that has resulted in a large gossan over the surface exposures surrounding the Project.