A new estimate of the surface composition of exposed parts of the Canadian Precambrian Shield has been obtained, using samples of 122 rocks from northern Quebec–Ungava, 116 from Baffin Island, 116 from southwestern Quebec, 64 from northeastern Alberta, 18 from northern Saskatchewan, and 8076 from northern Ontario. Where feasible an interpenetrating replicate sampling design was used, with probability weighting by rock-type, analyzing both individuals and composites for trace elements, but only composites for major elements, A total of 385 triplicate spectrographic analyses and 48 major-element analyses were made.Regional differences between the six samples were detected; whether these also include secular variations could not be studied. The overall estimate follows:[Formula: see text]The major elements are similar to those found in granditorite, mica paragneiss, or graywacke, but the trace elements agree better with the last two only. Data for Th and U will follow later.The Precambrian Shield of Canada (and Fennoscandia also) contains more Si and K, and less Ti, Fe, Mn, Mg, and Ca than recent estimates of the whole crust of the earth.
1. A series of 87 patients operated on because of subfrontal fractures is reported. In 73 of these a fistulous lesion (connecting the brain with the nose or the accessory air sinuses) was displayed and was repaired. Almost always a bifrontal exploration has been made, because the lesions were bifrontal in 43 per cent of cases. The mean follow‐up period was 4 years; to date no instances of postoperative meningitis or rhinorrhoea have occurred. 2. Our experience suggests that cerebrospinal rhinorrhoea accompanying fractures of the facial bones (without fractures of the skull vault) can safely be treated conservatively. 3. Damaged brain adheres to the lips of the torn dura and permanently prevents natural healing, thereby creating a continuing threat to life. Consequently it is recommended that all frontal fractures lying below the hairline and all comminuted anterior temporal fractures should be referred for expert neurosurgical/neuroradiological assessment. This is because 42 per cent of the patients requiring operative repair were selected after tomographic studies of the anterior fossa; they had not presented with the classic criteria of cerebrospinal rhinorrhoea, intracranial air, or meningitis.
An attempt has been made to estimate the abundance of trace and major constituents in the Precambrian surficial rocks of a large part (43 000 square miles) of the Red Lake–Lansdowne House area in northwestern Ontario. One-hundred and two composite samples were made to represent eight rock types in seven adjacent map-areas of equal size. Major element analysis was carried out on eight composite samples representing rock types for the whole area. Analysis of variance techniques have detected significant regional variations of Cr, Mn, Sr, and Ba. Significant variation exists between rock types for all trace elements analyzed except Cu.
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