摘要:

An unusual occurrence of gypsum-anhydrite at Falkland, British Columbia, that supplied more than 1 250 000 tons of commercial gypsum between its opening in 1926 and its closing in 1956, has been considered to be of hydrothermal replacement origin. Evidence is here presented to show that the gypsum-anhydrite bodies were originally deposited as part of a sedimentary sequence and that they have "intruded" into their present positions as lenses and smears by plastic mobility along well-marked fault zones that supplied avenues of migration rather than conduits for sulphate-rich solutions.

ISSN:0008-4077    

DOI:10.1139/e64-001

出版商:NRC Research Press    

年代:1964

数据来源: NRC

摘要:

The results of seismic refraction profiles on the Atlantic coast of Nova Scotia and on the continental shelf off Nova Scotia are presented. Compressional and shear waves have been observed in the crust and mantle and suggest that the thickness of the crust is about 34 km. The compressional wave velocities recorded in the main crust and upper mantle are 6.10 and 8.11 km s−1respectively. No compressional waves with values of velocity between these values can be identified, and this suggests that any "intermediate" layer is thin or absent. The corresponding shear wave velocities are 3.68 and 4.53 km s−1. Values of Poisson's ratio in the crust and mantle are 0.22 and 0.28. Alternative models of the crust which, on the evidence of travel times, might fit the observed results are discussed.

ISSN:0008-4077    

DOI:10.1139/e64-002

出版商:NRC Research Press    

年代:1964

数据来源: NRC

摘要:

The multivariate statistical techniques of component and factor analyses, when applied to major and trace element data presented by Shaw (1960), identify the Marialite–Meionite solid solution in scapolites and tentatively suggest the existence of an independent end-member bearing Mg and (OH). Three trace element factors suggest the groupingsIt is suggested that factor analysis may be a useful technique to apply to other complex mineral groups.

ISSN:0008-4077    

DOI:10.1139/e64-003

出版商:NRC Research Press    

年代:1964

数据来源: NRC

摘要:

The theoretical basis for the interpretation of the Alert anomaly in geomagnetic variations has been reexamined. Under the uniform horizontal inducing field approximation, the electromagnetic response of an infinite elliptical cylinder of infinite conductivity has been derived, and from this the response for the upheaval of a half-elliptical conductor from a highly conducting mantle. The results have been extended to an asymmetric upheaval of the conducting mantle. A theory has also been developed of the electromagnetic response of an elliptic cylinder which is useful for application to the finite conductivity case.The electromagnetic coupling between an infinite circular cylinder and an underlying conducting layer has been investigated as far as the second-order approximation. An exact solution has then been obtained for the infinite conductivity approximation, and useful examples calculated.The situation at Alert has been reexamined following this work which reduces one of the difficulties of the earlier interpretation. An upheaval of about 100 km of the 1400–1500 °C isotherm to within 25–30 km of the surface appears capable of accounting for the gross characteristics of the response but the solution is certainly not unique and may be in error by as much as 60%. The asymmetry in the response is difficult to explain quantitatively. The response parameters thought to be most useful have been clearly defined and the ambiguity in the electromagnetic response solutions illustrated. Suggestions for further progress are made. Brief mention is made of preliminary magnetotelluric and gravitational studies at Alert.

ISSN:0008-4077    

DOI:10.1139/e64-004

出版商:NRC Research Press    

年代:1964

数据来源: NRC

摘要:

A study has been made of several dozen small, stock-like ultramafic to mafic igneous bodies that occur in two clusters, 50 and 75 miles west of the head of Lake Superior. One cluster, the Quetico intrusions, is dominantly hornblende peridotite, hornblendite, and feldspathic hornblendite; the other, the Shebandowan intrusions, comprises serpentinized peridotite and subordinate gabbro. Both intrude eugeosynclinal deposits and are followed by extensive granitic, and minor syenitic intrusions, and both have associated Ni–Cu sulphides containing minor Pt and Pd.The Quetico intrusions are shown to have formed by fractional crystallization of tholeiitic olivine basalt liquid, possibly carrying suspended olivine and clinopyroxene when emplaced. Crystallization was at a water partial pressure of at least 2500 bars and, thus, a depth of 5 or more miles. The Shebandowan intrusions resemble alpine-type peridotite bodies structurally but, chemically and petrographically, are more like the differentiates of stratiform mafic intrusions. Their peridotite has formed from tholeiitic magma by early fractionation of olivine; the gabbro probably represents residual magmatic liquid. Serpentinization, which is postmagmatic, apparently has not caused extensive chemical change beyond addition of H2O, O2, and some CO2, and local redistribution of lime.The rocks in the two groups of intrusions differ appreciably in Cu and Ni, and a correlation between the Cu/Ni ratios of the rocks and their respective ores is illustrated. This correlation, and the sulphur isotopic composition, both indicate derivation of the sulphides from the intrusions.

ISSN:0008-4077    

DOI:10.1139/e64-005

出版商:NRC Research Press    

年代:1964

数据来源: NRC