Cargill Township carbonatite complex, District of ... - Geology Ontario

R. P. SAGE
Township and extends into the southwest corner of Cumming Township. The
complex can be most easily reached by the private, logging access road of Spruce
Falls Pulp and Paper Company Limited which passes within 1.6 km of the body.
The International Minerals and Chemical Corporation (Canada) Limited has
constructed a subsidiary road to a campsite on "Marilyn" Lake (local name)
located on the southern half of the complex.
The complex is dumbell-shaped and has a pronounced northeast elongation.
Its general outline is well displayed on aeromagnetic map 2252G (ODM-GSC
1962). The intrusion has a surface area of approximately 9.6 km2 (Figure 2).
Outcrop of the complex is rare, and consists of several small, deeply weathered
outcrops of pyroxenite and/or carbonatite.
Physiography
The complex is located in generally flat marshy ground and lacks significant topo
graphic relief. Relief is on the order of 15 m and reflects a topography of rounded
hills separated by wet ground.
Previous Geological Work
Bennett e t al. (1967, Figure 13) first mapped the complex as part of a regional
reconnaissance program and Gittins e t al. (1967) completed a K-Ar isotopic age
determination on the complex. Allen (1972) did detailed studies on the mafic
rocks on the complex using samples of diamond drill core obtained from Kennco
Explorations (Canada) Limited. Sandvik and Erdosh (1977) have published a
summary of the results of the work completed by the International Minerals and
Chemical Corporation (Canada) Limited on the residual apatite accumulations
lying above the bedrock.
Gasparrini et al. (1971) published a brief note on the compositions of the
amphibole and phlogophite found within the complex. In 1973, Kocman and
Rucklidge published data on the composition of clinohumite found at the Cargill
carbonatite. Gittins et al. (1975) have proposed that the phlogopite found in
close association with the pyroxenite at Cargill is the result of fenitization of the
pyroxenite by an intruding alkali-rich carbonatite magma.
In 1983, Twyman completed an extensive study of the carbonate-rich phases
and contained minerals. His study was an extension of the work completed by
Allen (1972) on the mafic silicate phases. Twyman (1983) made numerous com
parisons between the Cargill and the similar Argor carbonatite complex.
Kwon (1986) completed isotopic studies on the Cargill complex and Sharpe
(1987) completed work in Rb-Sr isotopic systems.
The volume of chemical, microprobe, and isotopic data is too voluminous to
present here and readers should refer to the original documents by Twyman
(1983) and Sharpe (1987).
Present Survey
Field sampling was completed in 1976. Due to lack of outcrop, sampling was
restricted to the diamond drill core of the International Minerals and Chemical
Corporation. All drilling consisted of vertical holes and diamond drilling was re
stricted to approximately 1200 m (4000 feet) in total core-length. The company
used reverse circulation techniques for most of its drilling which was primarily
done to investigate the residual accumulation of apatite above the bedrock.
As only diamond drill core samples were available it is likely that these sam
ples are not representative of the complex as a whole. Sampling emphasis was