|Title||Iron-oxide and alkali-calcic alteration ore systems and their polymetallic IOA, IOCG, skarn, albitite-hosted U±Au±Co, and affiliated deposits: a short course series. Part 1: introduction|
|Licence||Please note the adoption of the Open Government Licence - Canada
supersedes any previous licences.|
|Source||Geological Survey of Canada, Scientific Presentation 56, 2017, 80 pages, https://doi.org/10.4095/300241 Open Access|
|Publisher||Natural Resources Canada|
|Related||This publication is related to the following publications|
|Subjects||economic geology; geochemistry; igneous and metamorphic petrology; educational geology; mineral deposits; mineral exploration; exploration methods; polymetallic ores; hydrothermal deposits; magmatic
deposits; mineral deposits genesis; hydrothermal systems; alteration; facies; metasomatism; deformation; mineralization; iron oxides; models; mineral assemblages; albitites; albitization; brecciation; veins; skarns; epithermal deposits; geochemical
interpretations; thermal regimes; host rocks; mapping techniques; mineral occurrences; Great Bear Magmatic Zone; Central Mineral Belt; Makkovik Province; Romanet Horst; Labrador Trough; Bondy Gneiss Complex; Grenville Province|
|Illustrations||photographs; diagrams; location maps; geoscientific sketch maps; charts; graphs; flow charts; bar graphs; geochemical plots; schematic representations|
|Program||Targeted Geoscience Initiative (TGI-5) Uranium systems|
|Released||2017 11 07|
|Abstract||Worldwide, iron oxide copper-gold (IOCG) deposits form world-class mining districts. In a single deposit, such as Olympic Dam, resources can reach 10 billion tons at 0.78% Cu, 0.25kg/t U3O8, 0.30g/t Au,
1.0g/t Ag. Rare-earth resources can also be significant. Systems that form IOCG deposits also host many other deposit types. |
This short course illustrates the metasomatic growth of polymetallic magmatic-hydrothermal iron-oxide and alkali±calcic
alteration systems and the genetic linkages among their iron oxide-apatite (IOA), iron oxide copper-gold (IOCG) and affiliated deposit types, using the Great Bear magmatic zone (Northwest Territories, Canada) as a prime example. Complementary
information are also sourced from the Central Mineral Belt of the Makkovik Province (Labrador), the Romanet Horst of the Labrador Trough (Quebec) and the Bondy gneiss complex of the Grenville province (Quebec) in Canada as well as from deposits
The Great Bear systems are differentially uplifted, tilted, transcurrent-faulted, and locally exhumed. They escaped orogenic metamorphism and pervasive deformation. Their former sedimentary covers are largely eroded and Quaternary
glaciation left only a sporadic till cover. Consequently, outcrops are non-weathered, glacially polished and nearly continuous exposing in structural 3D the metasomatic growth of iron-oxide and alkali±calcic alteration ore systems from paleo-depth to
Within systems, metasomatism is pervasive and intense at regional to deposit scale. From paleo-depth to paleo-surface and away from heat sources (sub-volcanic intrusions), the diagnostic alteration facies prograde from: From depth
to surface and away from heat sources, the diagnostic alteration facies prograde from: Facies 1 Na, transitional Na-Ca-Fe and skarn; Facies 2 high temperature Ca-Fe; Facies 3 high temperature K-Fe; Facies 4 transitional K and K-skarn; Facies 5 low
temperature K-Fe (± low temperature Ca-Mg); and Facies 6 epithermal alteration.
The prograde, retrograde, telescoped and cyclical metasomatic reaction paths lead to a regular series of deposit types with varied metal associations and
mineralisation styles from paleo-depth to paleo-surface: Iron oxide-apatite (IOA) and their REE mineralised variants; Iron oxide copper-gold (IOCG) and low Cu, Co, Bi variants; Polymetallic potassic-skarns; Albitite-hosted U and Au-Co-U; Mo-Re and
other affiliated deposits.
Space-time relationships between metasomatism, magmatism, deformation and mineralisation constrain element addition and depletion in ore fluids from sources to deposits. They also record fluid pathways, sources of fluid
rejuvenation, and heat sources across the ore-forming environments. The information is synthesised into an ore deposit model adaptable to the variety of fluid (and potential melt) sources, host rocks and compositions these ore systems have.
petrological mapping protocols, rock nomenclatures, chemical map methodologies, discriminant chemical diagrams, and geological vectors to mineralisation stem from these findings. They collectively unify the complex and disparate attributes of these
ore systems into effective exploration concepts and provide a novel geoscience framework to explore Canada's prospective terrains for IOCG and affiliated deposits.
|Summary||(Plain Language Summary, not published)|
This series of short courses illustrates the metasomatic growth of polymetallic iron oxide and alkali-calcic alteration ore systems, using the Great Bear
magmatic zone (NWT, Canada) as a prime example. It also documents the genetic linkages among their iron oxide-apatite (IOA), iron oxide copper-gold (IOCG), albitite-hosted uranium (+ gold, cobalt), skarn and epithermal deposits and variants thereof.
Information on alteration facies and their space-time relationships with magmatism, deformation and mineralisation is synthesised into a holistic ore deposit model. Are also illustrated new field and chemical mapping protocols, rock nomenclatures,
discriminant chemical diagrams, and geological vectors to mineralisation. These tools and models collectively unify the complex attributes of these ore systems into effective exploration concepts and provide a novel geoscience framework to explore
Canada¿s prospective terrains for IOCG and affiliated deposits. Chapter one reviews many of these elements as an introduction to the short course series.