Geology & Mineralization

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Posted on June 01, 2013

Geological Setting

The geology chapter in the report is extensive in order to understand the rock types, the facies and the minerals associated with the iron ore mineralization very much related to the metallurgical test work. The lithology, mineralogy, grain size and metamorphism differ slightly between the deposits.

Deposit A

The rock types and the mineral descriptions, as well as the association, relation and the continuity in the field were summarized in a publication (Gregory, A.F. 1958), based on general knowledge of iron formations at that time. According to the Gregory description, all rocks in the area are of Precambrian age. The oldest rocks appear to be the Schist Complex, a series of schistose interbedded pyroclastics and sediments, including the magnetite iron formation. Much of the iron formation is a simple, uniform, laminated rock comprising fine to very fine grained quartz and magnetite with minor accessory minerals. Alternating laminae are black magnetite and white quartzite bands. They are variable in thickness from very fine to coarse (one inch) and often are highly contorted by flowage folding. The iron formation is estimated to vary from 30% to 60% magnetite with an average of about 45-50%. Intercalated schist horizons lower the grade. The iron formation occurs in essentially a homoclinal sequence with prominent satellitic folding. The homocline comprises the east limb of an inclined isoclinal anticline whose axis trends along the west edge of the present map area.

Deposit D

The following local geology description is directly taken from R.E. Jones (1959). The bodies of quartz-magnetite iron formation and associated garnetiferous schists are folded and isolated within a large area of granitic rock. In the metamorphic rocks, two major groups are recognized and termed Quartz Magnetite Iron Formation and Schist (generally garniteferous biotite schist). The deposit is a complexly folded body of quartz magnetite iron formation and associated schist isolated, at least for several miles along the surface, within the granite and granite gneiss. Metamorphism was not affected without severe structural changes. In general, iron formation occupies two synclines plunging gently south to southeastward, one to the west and the other to the east of the fault, are presumed to follow the central north-south trench.

Deposit E

The local geology description is directly taken from F.R. Edmunds (1960). The deposit consists of a series of ferruginous quartzite and minor schistose non-magnetic intercalations. Structurally, the deposit is an asymmetrical syncline, the axis of which plunges east at about 26°. A minor anticlinal development in the northern limb and intense local placations render the structure more complex. Two major groups are recognized and termed Schist and Iron Formation. The formations comprise an asymmetric syncline plunging to the east. The southern part appears to be dipping more steeply, and to be more tightly folded, to east-west, and is returned at its eastern extremity in a small anticlinal structure. The northern limb also develops into a subsidiary anticline, fading westwards towards its core, so that along the western contact of the deposit only the trough structure exists.

Great Whale Iron Property - MINERALIZATION

The mineralization is associated with iron ore formation unit commonly named Banded Iron Formation (BIF) present in the Deposits A, D, and E. The iron mineral is mainly magnetite with little amounts of hematite, martite and hydroxide iron (limonite) related to weathering. The relationship between geology and mineralization is very close, and has been discussed in Section 6 - Geology and Section 7 - Deposits Type.

To summarize the mineralization type, the iron ore formation is principally composed of recrystallized magnetite, fine to medium-fine grained, in a banded or lamellae iron ore rock for the Deposit A. Deposit E is mainly granular and disseminated, recrystallized, obliterated the sedimentary BIF aspect. Deposit D retains part of the BIF aspect and partially coarse disseminated grains. The waste and associated minerals are principally quartz, actinolite, tremolite, diopsite, grunerite, chlorite and biotite in proportionally decreasing order. The internal associated waste bands included in the ore are some mica schists bands. Probably some of these micas bands are related to the intense, squeezed and isoclinals folding. The average head grade varies from 34 to 37% Fe. The hematite content is very low or not present at all.

The iron ore facies sedimentation varies from fine banded or lamellae high grade iron content (2-3 mm to 1 cm bands) interlayered with waste bands (low grade disseminated bands), to more massive disseminated magnetite. The magnetite grain size varies from fine to medium-fine in Deposit A, medium-fine to coarse in the deposit D, to very coarse in the deposit E.

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