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File Created: 24-Jul-1985 by BC Geological Survey (BCGS)
Last Edit:  26-May-2021 by George Owsiacki (GO)

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NMI 094C5 Co1
Name BLOOM CIRQUE, CROY, CROY BLOOM Mining Division Omineca
BCGS Map 094C041
Status Prospect NTS Map 094C05W
Latitude 056º 28' 52'' UTM 10 (NAD 83)
Longitude 125º 58' 06'' Northing 6263575
Easting 317218
Commodities Copper, Gold, Cobalt Deposit Types L03 : Alkalic porphyry Cu-Au
Tectonic Belt Intermontane Terrane Plutonic Rocks, Quesnel
Capsule Geology

The Bloom Cirque occurrence is located on the west side of Bloom Creek cirque, 4 kilometres north of Kliyul Creek, approximately 110 kilometres northwest of the community of Germansen Landing.

The occurrence area is underlain by Upper Triassic volcaniclastic and volcanic rocks of the Takla Group, which have been intruded by the Croydon Creek ultramafic stock, the Croydon Creek pluton, the Kliyul Creek pluton and a host of related dikes (part of the Late Triassic to Early Jurassic Aiken Lake Intrusive Complex). These intrusive bodies comprise the northern end of the Early Jurassic to Early Cretaceous Hogem Plutonic Suite, a multiphase intrusive complex with latest Triassic to Middle Jurassic alkaline phases and Cretaceous calc-alkaline bodies. Compositional similarities, subvolcanic phases and heterolithic volcanic-subvolcanic intrusive assemblages are thought to be in part, coeval with the ultramafic stock and Croydon Creek pluton. Coarsely recrystallized hornfelsed rocks or an intrusive breccia commonly marks the contact between Takla volcano-sedimentary rocks and Hogem intrusive bodies.

Diamond drilling was conducted in 2008 on behalf of Newcrest Mining BC Ltd. and Serengeti Resources Inc. on their large Croy-Bloom/Davie Creek project. Drillhole CBB001 was drilled in the upper portion of the Bloom cirque and tested an open chargeability anomaly and resistivity low. The drillhole intersected scattered zones of weak copper-gold mineralization from surface to a depth of 510 metres. Mineralization is predominantly structurally controlled, contained within or adjacent to breccia bodies and in quartz veins. Breccias are typically intrusive, though some have minor hydrothermal components. Intrusive breccias comprise sub-angular clasts of fine-grained diorite plus/minus minor pyroxene-phyric andesite in diorite cement. Hydrothermal breccias are generally less than 1 metre thick and consist of in situ 1 centimetre-sized angular clasts of diorite in epidote cement. Breccia bodies vary from less than 1 metre to 55 metres and typically have between 500 parts per million to 0.1 per cent copper. Their geometry is unknown, however, some contacts suggest they are gently dipping (no oriented core measurements were taken). Weak gold mineralization (approximately 0.1 gram per tonne) is developed around the margins of breccia bodies and contacts of intrusive units. Slightly higher gold values were recorded from quartz veins (1.0 metre at 0.8 gram per tonne gold and 1.0 metre at 0.4 gram per tonne gold).

Chalcopyrite is the dominant copper sulphide and occurs mostly with pyrite as open-space fillings of fractures or in quartz veinlets (less than 5 millimetres thick). Secondary biotite-magnetite-epidote-sericite plus/minus albite alteration is commonly associated with mineralized zones often with pseudo breccia/false polymictic textures.

Alteration and mineralization intersected in drillhole CBB001 appears typical of the inner propylitic zone surrounding a potassic core in an alkalic porphyry model. The intrusive breccias appear to have been an important structural control in promoting pathways and open space for copper-gold mineralization on the eastern half of the Bloom Cirque. Comparisons to other porphyries in the district would also suggest CBB001 is marginal to possible higher-grade copper mineralization. The drillhole ended in strongly chlorite-altered andesite at 687.94 metres (Assessment Report 30937).

Drillhole CBB002 was drilled 160 metres to the southwest of drillhole CBB001 in the lower portion of the Bloom cirque and tested a chargeability anomaly and resistivity low. The drillhole intersected narrow zones (less than 12 metres wide) of discontinuous copper plus/minus gold mineralization. Mineralization appears to be less structurally controlled than in CBB001 and occurs in shear and fracture zones, narrow quartz veins and disseminations in diorite. Gold is negligible with only two anomalous intercepts for the entire hole (2.0 metres at 0.1 gram per tonne gold and 2.0 metres at 0.5 gram per tonne gold). Chalcopyrite is the dominant copper sulphide mineral in drillhole CBB002 and generally occurs in narrow (less than 1 centimetre) sheeted crystalline quartz plus/minus carbonate veins and micro-stockwork veinlets. Chalcopyrite is also observed as disseminations, replacements, fracture-controlled blebs and narrow (less than 1 millimetre thick) discontinuous stringers. The highest copper values (0.2 per cent) coincide with intense magnetite plus biotite-dominated alteration assemblages. Mineralization is hosted in fine- to medium-grained diorite and minor (less than 10 metres thick), pyroxene-phyric andesite and pyroxenite dikes. A 24.3-metre-wide feldspar-phyric trachyandesite porphyry dike crosscuts diorite from 298.7 metres. The trachyandesite is unmineralized. Mineralization is associated with texturally destructive secondary biotite-magnetite-epidote-sericite plus/minus potassium-feldspar plus/minus albite alteration often with pseudo breccia/false polymictic textures. The drillhole ended in moderately sericite-epidote-albite altered diorite at 712.33 metres (Assessment Report 30937).

Early work in the occurrence area referred to "a little cobalt bloom was also observed coating fractures in small quartz veins in hornblende diorite east of Croyden Creek" (Geological Survey of Canada Memoir 274, page 202). In addition, Assessment Report 21521 (volume 1, page 24) reports minor cobalt bloom on fracture surfaces on the west side of Bloom cirque. Assessment Report 21521 also reports minor occurrences of fracture controlled and disseminated chalcopyrite, malachite and pyrite throughout a fine-grained phase of the "Croydon Creek pluton" (Bloom Creek diorite), a Jurassic or older intrusion possibly related to the Late Triassic to Early Jurassic Aiken Lake Intrusive Complex. The fine-grained phase consists of hornblende diorite and quartz diorite and is located at the north end of Bloom cirque and on the ridge to the southeast. Mineralization is also reported to extend into the pegmatitic phase of the intrusion on the west side of Bloom cirque. Disseminated and stringer magnetite is also reported in the area (Assessment Report 21521, Geology Map, East Half). Widespread weak to strong propylitic alteration (epidote and chlorite) accompanies the mineralization.

In 1990, Teck Exploration Ltd. acquired a large portion of the current (ca. 2008) Croy-Bloom/Davie Creek property and commenced an extensive exploration program. The purpose of the program was to evaluate the potential for an alkalic porphyry copper-gold deposit. Between 1990 and 1991, they conducted geological mapping, soil/rock chip sampling and an induced polarization survey. The work defined large copper-gold anomalies at the Raven prospect (094C 127) and in the Bloom Cirque (094C 039, this description). Three holes (totalling 450 metres) were drilled at Raven where two of the holes intersected weak copper and gold mineralization.

In 2002, Northgate Minerals flew an airborne magnetic/radiometric/EM survey and conducted limited rock and core sampling.

Between 2007-08, Serengeti Resources Inc. carried out heliborne magnetic and radiometric surveying over the Croy Bloom and Kem properties totalling 2322 line-kilometres. In 2008, Newcrest Mining BC Ltd. and Serengeti Resources Inc. drilled a total of 2472.88 metres of NQ2 core in four surface holes on their Croy-Bloom/Davie Creek project. Two of the four holes (CBB001 and CBB002) totalling 1400.27 metres were drilled on the Bloom Cirque prospect. Both holes tested targeted a 1.8 by 1.0 kilometre gold-copper soil/rock anomaly that is coincident with a circular zone of plug-like airborne magnetic anomalies. These anomalies are associated with highly fractured, moderate to strongly biotite-potassium-magnetite-epidote-sericite altered diorite/andesite and widespread chalcopyrite-malachite mineralization at surface.

Bibliography
EMPR ASS RPT *21521, 27869, 30054, *30937, 35191
EMPR FIELDWORK 1991, pp. 127-145; 1992, pp. 109-134; 2018, pp. 31-53; 2019, pp. 25-47
EMPR OF 1992-11; 1993-2
EMPR P 1992-01, pp. 127-145; 1993-01, pp. 109-134; 2019-01, pp. 31-53; 2020-01, pp. 25-47
EMPR PFD 673269
GSC MAP 1030A
GSC MEM *274, p. 202
GBC 2021-01, pp. 105-120
PR REL Serengeti Resources Inc. Nov.18, 2004, May 31, Nov.15, 2005, Jan.21, 2009
N MINER Jun.6-12, 2005

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