ALBERT

Notes: Abstract The vein-type gold deposits of middle to late Archean age constitute one of the major sources of gold production in the world. These deposits are highly diverse in character, but are invariably found in proximity to mafic and ultramafic volcanic rocks, and closely associated with tectonically disturbed zones, or ‘breaks’, in the ancient crust. Using the Larder Lake ‘break’ of northern Ontario and Quebec as a model, a general theory of genesis for such deposits is proposed. The Larder Lake ‘break’ is of linear configuration, up to four miles wide, and extending over a distance of approximately 150 miles. Many rich and extensive vein-type gold deposits are associated with it. This ‘break’ is recognized as a highly folded and faulted, dominantly sedimentary stratigraphic unit, formed as part of the development of the Blake River geosyncline of the Abitibi greenstone belt. Faulting is pervasive within the ‘break’ but it is non-continuous. Under an oxygen-poor, somewhat acidic weathering regime believed extant in Archean time, gold and associated constituents, derived as weathering products from mafic and ultramafic volcanics, appear to have been concentrated as solutions and sols in muddy surficial accumulations along a paleo-continental margin. On transfer to a shallow marine environment, the gold-bearing solutions became concentrated mainly as cherty and pyritic evaporitic residues. These residues, infolded and variably metamorphosed and remobilized during ensuing geosynclinal development, formed the numerous and apparently heterogeneous gold deposits of the Larder Lake ‘break’. Mode of redistribution of gold-bearing residues and metamorphism of their host rocks varies widely. In mild form, little vein development is present and original sedimentary features of the host rock are often preserved. In more extreme cases, true hydrothermal veining is evident and complete recrystallization of the host rock has taken place, sometimes to the extent of formation of a melt with intrusive capabilities. In any case, the gold and related vein constituents remain closely associated with the primary host material and alteration effects are largely derived from the recrystallization of original host rock constituents. The suggested mode of genesis clarifies the relationship between various types of ‘break’-related, vein-type gold deposits and offers an explanation of the complex stratigraphy and structure of the ‘break’ environment. It also suggests a penecontemporaneous relationship between the Larder Lake ‘break’ and other auriferous ‘breaks’, of varying configuration, within the Superior Province of the Canadian Shield. The concept can be used advantageously in exploration for new ‘breaks’ and new deposits.

Notes: Summary Previous studies of stocks of two Mutator-induced mutable a1 alleles (a1-Mum2 and al-Mum3) gave results consistent with the presence of one or more autonomous elements regulating the expression of mutability. This article reports on the results of studies designed to map these autonomous elements by using a series of waxy marked translocations. Linkage of waxy with autonomous elements was found for a1-Mum2 by using the translocations wx T2-9d, wx T4-9e and wx T4-9b. Several different linkage values were found in crosses involving wx T2-9d, suggesting that autonomous elements have transposed to different locations on chromosome 2. Linkage of autonomous elements with waxy was found for a1-Mum3 using translocation wx T2-9d. Again, several different linkage values were found. Some of these values were the same as those observed for a1-Mum2, but some were unique. In some crosses, the number of autonomous elements increased by one or two unlinked elements in addition to the linked element in one generation (i. e. the generation of the cross to the translocation series). Such an increase in number is probably the result of transposition of the original autonomous element to an independent locus while retaining the autonomous element at the original locus. Reduction in the number of autonomous elements is probably the result of the independent assortment in crosses of plants with two or more autonomous elements.

Notes: Abstract The determination of dislocation densities and distributions in III–V compounds by etching techniques frequently leads to erroneous results, especially where high densities are involved. The paper reports the use of a HNO3∶HCl∶Br etch on slices of InP and GaP and specifies the conditions under which the etch may be used as a precise guide to the dislocation density and distribution. Comparison of etch-pit micrographs and X-ray Lang topographs is used to establish the validity of the etching technique and to obtain information on the type, density and distribution of dislocations in substrates and epitaxial layers.

Notes: Abstract The results of a further study of the cadmium oxide-tungsten oxide phase diagram are presented and the results of attempts to prepare single crystals of cadmium tungstate. The defects encountered in the crystals and attempts to eliminate them are described and the best conditions for growth of high-quality single crystals detailed. The relationship of the defects to the crystal growth mechanism is discussed.

Notes: Abstract The conditions required to grow high quality lithium tetraborate single crystals are described, along with the defects likely to be encountered during growth of the crystals. The relationship of the latter to the growth mechanism is discussed and a mechanism proposed which provides an explanation of the observed nature of the defects and of the manner in which the crystals grow and reject impurities.