Ontario Geological Survey
Permanent Link to this Record:
MDI000000000170
| Record Name(s) | July Falls Mafic Stock Occurrence - 1948 |
|---|---|
| Related Record Type | |
| Related Record(s) | |
| Record Status | Occurrence |
| Date Created | 2006-Nov-14 |
| Date Last Modified | 2022-Jun-09 |
| Created By | |
| Revised By |
Primary Commodities: Gold
Township or Area: Collishaw Lake Area
Latitude: 51° 39' 50.08" Longitude: -89° 52' .02"
UTM Zone: 16 Easting: 301750 Northing: 5727550 UTM Datum: NAD83
Resident Geologist District: Thunder Bay North
NTS Grid: 52P12NW
Point Location Description: Obtained from Map P.3057
Location Method: Data Compilation
1947: Prospecting and trenching by Central patricial Gold Mines and Conwest Explorations.
| Office File Number | Online Assessment File Identifier | Online Assessment File Directory |
|---|---|---|
| 52P12NW15 | 52P12NW9481 | 52P12NW9481 |
| 2.13392 | 52P12NW0005 | 52P12NW0005 |
Province: Superior
Subprovince: Uchi
Terrane: North Caribou
Domain: Uchi
Belt: Pickle Lake
Geological Age: Archean
Nov 14, 2006 (Mark Puumala) - The July Falls area occurrences are located at the northeast end of the Pickle Lake Greenstone Belt. These occurrences are found within a mafic metavolcanic rock dominated supracrustal sequence identified by Young (2003) as being part of the > 2860 Ma Pickle Crow Assemblage, and within a mafic intrusion referred to by Stott (1996) as the July Falls Mafic Stock. According to Young (2003), the Pickle Crow assemblage is dominated by massive and pillowed mafic metavolcanic flows with subordinate gabbroic sills. The mafic metavolcanics are intercalated with thin, laterally continuous banded iron formation and small, discontinuous lenses of intermediate metavolcanics. All lithologies are intruded by semi-concordant feldspar porphyry dikes. Stratigraphy generally faces toward the northwest, except where asymmetric folding (mainly in the Pickle Crow mine area) has caused reversals in the younging direction (Young 2003). The July Falls Mafic Stock is described by Stott (1996) as a composite mafic stock consisting of phases ranging from quartz diorite to gabbro, pegmatitic gabbro and hornblendite. The structural geology of the July Falls Area is described by McAuley and Winter (1990). The earliest structures in the area appear to parallel the volcanic stratigraphy and strike approximately north-northeast to northeast. These structures are interpreted by McAuley and Winter (1990) to be cross-cut by later 060-striking shears. These shears are in-turn cross-cut by later shear/fault zones that strike approximately 335 and 100-120 respectively. These and the east-west-striking veins observed at the July Falls No. 1 prospect appear to be similar to the structures mapped by MacQueen (1987) at the Pickle Crow mine property. McAuley and Winter (1990) have interpreted mineralization at the three July Falls area gold prospects/occurrences to have a close spatial association with the intersection of the 060 and 335-striking structures.
| Rock Type | Rank | Composition | Texture | Relationship | Gabbroid-Unsubdivided | 1 | Contains |
|---|
| Rank | Mineral Name | Class | Economic Mineral Type | Alteration Mineral Type | Alteration Ranking | Alteration Intensity | Alteration Style |
|---|---|---|---|---|---|---|---|
| 1 | Pyrite | Economic | Ore | ||||
| 2 | Chalcopyrite | Economic | Ore | ||||
| 3 | Pyrrhotite | Economic | Ore |
Nov 14, 2006 (Mark Puumala) - Lytle (1948) reported the occurrence of gold mineralization within the July Falls Mafic Stock. The mineralization occurs in a narrow, contorted quartz vein that is mineralized with chalcopyrite, pyrrhotite and pyrite. The mineralization and structure at this location were described by Lytle (1948) as being similar to that found at the Little July Falls Prospect. An assay of 0.03 oz/ton Au was reported from a grab sample collected from this vein.
| Rank | Classification |
|---|---|
| 1 | Lode (Gold) |
| 2 | Vein |
| Rank | Characteristic |
|---|---|
| 1 | Vein |
Date: Jul 19, 2007
Geologist: Mark Puumala
Notes: An attempt to locate this occurrence in the field on July 19, 2007 was unsuccessful, as the occurrence location shown on previous OGS maps is in an area of thick, sandy overburden. Therefore, it is likely that this occurrence is located 500 to 1000 m further to the southeast, in an area where a number of outcrops were mapped by Stott et al. (1989).
Map - Geological series, Precambrian geology, Pickle Lake area, eastern part
Publication Number: P3057 Scale: 1:50,000 Date: 1989
Author: Stott G.M., Brown G.H., Coleman V.J., Green G.M., Reilly B.A.
Publisher Name: Ontario Geological Survey
Location:
Map - Cat Lake-Pickle Lake, geological compilation series, Kenora and Thunder Bay districts
Publication Number: M2218 Scale: 1:253,440 Date: 1976
Author: Sage R.P., Breaks F.W., Troup W.R.
Publisher Name: Ontario Division of Mines
Location:
Mono - The Geology and Tectonic History of the Central Uchi Subprovince
Publication Number: OFR5952 Date: 1996
Author: Stott G.M.
Publisher Name: Ontario Geological Survey
Location:
Thesis - New Structural, Geochronological, and Geochemical Constraints on the Tectonic Assembly of the Archean Pickle Lake Greenstone Belt, Uchi Subprovince, Western Superior Province
Publication Number: MSc Thesis Date: 2003
Author: Young, M.D.
Publisher Name: Queen's University
Location: Thunder Bay RGP
Thesis - Stratigraphy, Structure and Gold Mineralization of the No. 5 Vein/Iron Formation Zone, Pickle Crow Gold Mines, Pickle Lake, Ontario
Publication Number: MSc Thesis Date: 1987
Author: MacQueen, J.K.
Publisher Name: Carleton University
Location: Thunder Bay RGP
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