| Title | Setting and evolution of the Archean synvolcanic Mooshla Intrusive Complex, Doyon-Bousquet-LaRonde mining camp, Abitibi greenstone belt: emplacement history, petrogenesis and implication for Au
metallogenesis |
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| Author | Galley, A G; Lafrance, B |
| Source | A Special Issue on Archean Magmatism, Volcanism, and Ore Deposits: Part 2. Volcanogenic Massive Sulfide Deposits; by Mercier-Langevin, P (ed.); Gibson, H L (ed.); Hannington, M D (ed.); Goutier, J (ed.);
Monecki, T (ed.); Dubé, B (ed.); Houlé, M G (ed.); Economic geology and the bulletin of the Society of Economic Geologists vol. 109, 2014 p. 205-229, https://doi.org/10.2113/econgeo.109.1.205 |
| Image |  |
| Year | 2014 |
| Alt Series | Earth Sciences Sector, Contribution Series 20110292 |
| Publisher | Society of Economic Geologists |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf |
| Province | Quebec |
| NTS | 32D/01; 32D/02; 32D/07; 32D/08 |
| Area | Bousquet; Doyon |
| Lat/Long WENS | -78.5867 -78.4150 48.2958 48.2200 |
| Subjects | igneous and metamorphic petrology; metallic minerals; geochronology; geochemistry; emplacement; Archean; tectonic setting; petrogenesis; metallogeny; gold; volcanic rocks; sulphide deposits;
volcanogenic deposits; alteration; sills; dykes; lithology; tonalites; plutonic rocks; trondhjemites; diorites; rhyolites; schists; dacites; basalts; andesites; uranium lead dates; zircon dates; deformation; whole rock geochemistry; modelling;
Mooshla Intrusive Complex; Abitibi Greenstone Belt; Hebecourt Formation; Bousquet Formation; Orion Fault; Precambrian |
| Illustrations | geological sketch maps |
| Program | Targeted Geoscience Initiative (TGI-4) Gold Ore Systems |
| Released | 2013 11 19 |
| Abstract | The synvolcanic Mooshla Intrusive Complex intrudes coeval ~2699 to 2696 Ma volcanic rocks of the Blake River Group within the southern margin of the Archean Abitibi greenstone belt. The upper Blake
River Group is host to the Doyon-Bousquet-LaRonde mining camp that contains Au-rich volcanogenic massive sulfide (VMS) deposits, possible subsea-floor epithermal-style deposits, and orogenic Au deposits. In total, the camp contains to date in excess
of 28 million ounces (Moz) Au, making it a world-class example of Au-rich paleoseafloor environments. The Mooshla Intrusive Complex is spatially, temporally, and most probably genetically associated with all of the above types of mineralization. It
is host to parts of the Doyon (5.5 Moz Au), Mouska (0.8 Moz Au), and Mic Mac (0.11 Moz Au) Au deposits and host to the smaller Mooshla A and B Au occurrences. Host volcanic units to the Mooshla Intrusive Complex are intensely deformed, metamorphosed,
altered, and mineralized, as is the intrusion itself.
The Mooshla Intrusive Complex was formed by nine distinctive phases of subvolcanic dikes, sills, and stocks. These were emplaced in two stages to form a shallow, multiphase synvolcanic
intrusion along the contact between the Hebecourt and Bousquet volcanic formations. The Mouska stage is represented by a preliminary swarm of thin diabase sills, intruded by a well-layered gabbroic sill, a more crudely layered quartz diorite, and
tonalite. A period of devolatilization accompanied crystallization of the xenolith-rich top of the tonalite magma chamber, as evidenced by the presence of an aplite dike swarm and associated extensive alteration zones and miarolitic cavities. The
younger Doyon stage comprises a series of fine-grained aphyric to porphyritic, tonalite and trondhjemite dikes and sills, which also contain evidence of in situ devolatilization.
The geochemical signatures of the Mooshla Intrusive Complex
indicate emplacement during formation of an evolved, extensional oceanic island arc-style succession. Primitive mantle-normalized spider plots suggest a common origin for this island-arc intrusive suite that is similar to that of the volcanic
succession of the upper member of the Bousquet Formation. Various element ratio plots used to further define magma origin and emplacement history suggest that whereas the Mouska-stage magmatic phases have a relatively straightforward, coexisting
fractionation history, the Doyon-stage tonalite-trondhjemite has a more complex interplay of assimilation-fractionation-contamination, suggesting midcrustal partitioning and interaction with both earlier formed, partially hydrated ~2720 Ma oceanic
crust and upper Blake River host strata (~2699?2696 Ma). The protracted and mulitphased magmatic evolution of the Mooshla Intrusive Complex led to the generation of volatile-rich phases that contributed to the development of a submarine
magmatic-hydrothermal system that is thought to be responsible for the formation of the Doyon Au-Cu deposit. Geologic and timing relationships suggest that this magmatic-hydrothermal system might also have contributed to the generation of Au-rich VMS
deposits higher in the host volcanic succession as part of a large Archean magmatic and hydrothermal center. |
| GEOSCAN ID | 289626 |
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