Physical Volcanology and Hydrothermal Alteration of the Sturgeon Lake Caldera Complex

Morton, Ronald; Hudak, G. J.; Walker, Jamieson Scott; Franklin, J M

doi:10.4095/132357

Cited by 3 publications

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“…4b), down to matrix-sized material; the typical size is 3 to 25 cm. Detailed mapping and core logging also indicates that there are larger blocks of the Darkwater scoria-tuff cone deposits which measure more than 100 m in length and thickness (Morton et al, 1990). Matrix material for the clasts varies from abundant alteration and metamorphased alteration minerals (chloritoid, iron carbonate, andalusite, pyrophyllite, sericite, chlorite) to material very similar to the interlayered and overlying ashflow tuff.…”

Section: Introductionmentioning

confidence: 98%

“…The regional geology and the precaldera rocks have been described by Groves et al (1988) and by Morton et al (1990); the alteration and associated volcanic rocks of the Mattabi deposit have been classified by Morton and Franklin (1987). This paper briefly describes the major characteristics of the Sturgeon Lake Caldera Complex through the eruption and deposition of the submarine Mattabi ash-flow tuff and the relationship of this unit to the Mattabi massive sulfide deposit.…”

Section: Introductionmentioning

confidence: 98%

“…2) has an age similar to the telsic volcanics and represents, in part, the magma chamber for the eruptive material. The Beidleman Bay Complex also hosts minor occurrences of porphyry copper-molybdenum-type mineralization, and the upper parts locally contain stringers of zinc-silver mineralization (Franklin et al, 1976;Morton et al, 1990). A marie (gabbroic-quartz dioritic) dike to locally sill-like intrusion occurs across the length of the caldera complex ( Caldera collapse caused large blocks and smaller clasts of these lavas and scoria-tuff cone deposits to slide into the caldera, where they now form a major component of the various mego-and mesobreccia units (Fig.…”

Section: Introductionmentioning

confidence: 98%

“…2). Based on the stratigraphic distribution and thicknesses of the five ash-flow tuff units and associated debris flow deposits, it has been interpreted by Morton et al (1990) that the Sturgeon Lake caldera represents a series of smaller nested or overlapping calderas and that each ash-flow unit is associated with a collapse event.…”

Section: Introductionmentioning

confidence: 99%

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The early development of an Archean submarine caldera complex with emphasis on the Mattabi ash-flow tuff and its relationship to the Mattabi massive sulfide deposit

Morton¹,

Walker²,

Hudak³

et al. 1991

Economic Geology

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The south Sturgeon Lake area of northwestern Ontario is underlain by an Archean submarine caldera complex which is host to six massive sulfide deposits. The complex is approximately 30 km in strike length and is partly filled by mesobreccias, subaqueous debris-flow deposits and other epiclastic rocks, as well as five major ash-flow tuff units. The most voluminous of these, the Mattabi ash-flow tuff, is up to 800 m in thickness and can be traced for more than 15 km across the caldera complex. Based on flow morphology and composition, the Mattabi ash-flow tuff is divisible into two distinct units: a bedded quartz crystal and pumice-rich unit (150-650 m thick), and a massive to poorly bedded ash unit (20-150 m thick). The bedded unit is host to the Mattabi massive sulfide deposit, as well as numerous other massive sulfide occurrences. In addition, this unit exhibits a pronounced stratigraphic and geochemical cyclicity. Individual beds (flow units) can be subdivided into basal quartz-and pumice-rich lower sections which are overlain by bedded ash tops; thicknesses of individual beds vary from 14 to 155 m. Each bed also exhibits a pronounced zonation of trace elements with high concentrations of Zr, Y, and Nb at and/ornear the base gradually decreasing upward into the ash tops. The overlying massive ash unit contains no known massive sulfide mineralization and lacks any pronounced geochemical zoning.The bedded nature and geochemical zonation of individual flow units can be explained by periodic eruptions from a zoned or layered, recharged siliceous magma chamber. The difference in flow morphology between the bedded unit and the overlying massive ash-flow tuff most likely reflects the deeper submarine nature of the eruptive vents associated with the bedded deposits. The periodic and subaqueous nature of the Mattabi eruptions is indicated by the presence of exhalites and massive sulfide lenses between flow units. The ore lenses, which comprise the Mattabi deposit, formed between eruptive events from high temperature fluids whose origin may be related to processes within the magma chamber.

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Section: Introductionmentioning

confidence: 98%