Petrography, geochemistry and magnetic susceptibility of the Isortoq Fe-Ti-V deposit, Isortoq Giant Dykes, South Greenland
Open Access
- 21 August 2020
- journal article
- research article
- Published by Geological Survey of Denmark and Greenland in GEUS Bulletin
Abstract
The Isortoq Giant Dykes in the Proterozoic Gardar Province, South Greenland, includes Isortoq South giant dyke and Isortoq North giant dyke. The fine-grained Fe-Ti-V deposit hosted by the Isortoq South giant dyke, referred to as the Isortoq Fe-Ti-V deposit, is considered a good test site for the use of magnetic susceptibility for the mapping of ore grades. Here, we test this and show that the Fe, Ti and V distribution is controlled by titanomagnetite disseminated throughout fine-grained troctolite. The deposit displays a clear correlation between magnetic susceptibility and Fe, Ti and V grades in bulk samples of consecutive 2 m sections from 11 drill cores, totalling 2671 m in length. We observe that Fe, Ti and V are almost entirely hosted in titanomagnetite, which controls the magnetic susceptibility. Field measurements of the magnetic susceptibility can thus be considered as a reliable exploration tool for this type of mineralisation. We further consider the origins of the deposit by reconnaissance petrography, mineral and bulk rock chemistry of the large mass of aphanitic Fe-rich troctolite in the Isortoq South giant dyke. We suggest that the deposit may represent the base of a basanitic to trachybasaltic magma chamber, in which Fe-rich immiscible melts accumulated, crystallised and fractionated. The processes suggested here may apply to other giant dykes and intrusions of the Gardar Province.Keywords
This publication has 6 references indexed in Scilit:
- Elemental Distributions and Mineral Parageneses of the Skaergaard PGE–Au Mineralization: Consequences of Accumulation, Redistribution, and Equilibration in an Upward-Migrating Mush ZoneJournal of Petrology, 2019
- Petrological and geochemical characteristics of Mesoproterozoic dyke swarms in the Gardar Province, South Greenland: Evidence for a major sub-continental lithospheric mantle component in the generation of the magmasMineralogical Magazine, 2015
- Experiments on liquid immiscibility along tholeiitic liquid lines of descentBeiträge zur Mineralogie und Petrographie, 2012
- Physical properties and petrologic description of rock samples from an IOCG mineralized area in the northern Fennoscandian Shield, SwedenJournal of Geochemical Exploration, 2009
- Physical properties of rocks from borehole TJ71305 and geophysical outline of the Tjårrojåkka Cu-prospect, northern SwedenOre Geology Reviews, 2007
- Geophysical and petrophysical study of an iron oxide copper gold deposit in northern SwedenOre Geology Reviews, 2006