THE MICHIKAMAU ANORTHOSITIC INTRUSION, LABRADOR

1965 ◽  
Vol 2 (4) ◽  
pp. 385-399 ◽  
Author(s):  
Ronald F. Emslie
Keyword(s):  
Bulk Composition ◽  
Olivine Basalt ◽  
Secondary Alteration ◽  
Essential Minerals ◽  
Iron Enrichment ◽  
End Products ◽  
Basaltic Liquid

The Michikamau Intrusion is a large, unmetamorphosed anorthositic mass lying within the broad belt of anorthositic bodies extending from southeastern Ontario to Labrador. Potassium–argon biotite dates place the time of crystallization of the intrusion at approximately 1 400 million years ago.The main rock units of the intrusion are leucotroctolite, anorthosite, and leucogabbro; essential minerals are plagioclase, olivine, clinopyroxene, and orthopyroxene. The bulk of the plagioclase falls in the range An52–An62 and olivine in the range Fo60–Fo70. The rocks are remarkably fresh and free from secondary alteration products.A number of features characteristic of large, layered basic plutons are present in the Michikamau Intrusion. The chilled margin has the composition of olivine basalt. However, the bulk composition of the mass is highly feldspathic, thus leading to the proposition that the basaltic liquid was heavily charged with plagioclase crystals. Cumulate structures and textures indicate that bottom accumulation of crystals may have played an important part in the solidification and differentiation of the intrusion.The course of differentiation of the magma was toward extreme iron enrichment with the development of ferrous-rich dioritic, granodioritic, and syenitic rocks as end products. It is unlikely that water played an important role in the crystallization of the intrusion.

The loss of Fe and Na from a basaltic melt during experiments using the wire-loop method

1979 ◽  
Vol 43 (325) ◽  
pp. 121-126 ◽  
Author(s):  
Gay Corrigan ◽  
Fergus G. F. Gibb
Keyword(s):  
Electron Microprobe ◽  
Direct Contact ◽  
Bulk Composition ◽  
Wire Loop ◽  
Alloy Wire ◽  
Loop Method ◽  
Inverse Proportion ◽  
Basaltic Melt ◽  
The Wire ◽  
Basaltic Liquid

SummaryLosses of Fe and Na from a typical basaltic liquid during experiments using the wire-loop method have been determined for both Pt and Ag40Pd60 alloy wire by electron-microprobe analyses of the quenched glasses. The amount of Fe lost is dependent on the duration of the experiment and is particularly sensitive to the ratio of sample to metal in direct contact with it. Fe losses can be minimized by using the thinnest wire possible in conjunction with the largest amount of sample that will adhere to the wire and, if Ag-Pd wire is used, can be kept below the 1% level even in long experiments. Much more serious in terms of changes in the bulk composition are losses of Na, which appear to be in direct linear proportion to the length of the experiment and in inverse proportion to the mass of the sample. Even when samples in excess of 200 mg are used the Na losses are unlikely to be less than 5% except in experiments of less than a few days' duration or on samples with very low initial Na contents.

Quantitative Analysis Of X-Ray Images From Geological Materials

1990 ◽  
Vol 48 (2) ◽  
pp. 244-245
Author(s):  
J. M. Paque ◽  
R. Browning ◽  
P. L. King ◽  
P. Pianetta
Keyword(s):  
Quantitative Analysis ◽  
Bulk Composition ◽  
Principal Component ◽  
Analytical Description ◽  
Bulk Sample ◽  
Geological Samples ◽  
X Ray ◽  
Software And Hardware ◽  
And Storage ◽  
Insight Into

Geological samples typically contain many minerals (phases) with multiple element compositions. A complete analytical description should give the number of phases present, the volume occupied by each phase in the bulk sample, the average and range of composition of each phase, and the bulk composition of the sample. A practical approach to providing such a complete description is from quantitative analysis of multi-elemental x-ray images.With the advances in recent years in the speed and storage capabilities of laboratory computers, large quantities of data can be efficiently manipulated. Commercial software and hardware presently available allow simultaneous collection of multiple x-ray images from a sample (up to 16 for the Kevex Delta system). Thus, high resolution x-ray images of the majority of the detectable elements in a sample can be collected. The use of statistical techniques, including principal component analysis (PCA), can provide insight into mineral phase composition and the distribution of minerals within a sample.

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