Electronic Resource
Oxford, UK
:
Blackwell Publishing Ltd
Sedimentology
17 (1971), S. 0
ISSN:
1365-3091
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Geosciences
Notes:
Samples from an uninterrupted sequence of Early Precambrian graywackes were investigated in order to disclose whether the amount of “volcanic” quartz, i.e., quartz without undulatory extinction, can give indications of quantitative changes in the composition of the source area. As non-undulatory quartz usually is enriched in the smaller-size fractions, only grains with an above average grain size were considered. The minimum grain size was fixed at 0.1 mm. In each thin section 100 grains were counted and separated into two groups, one without and one with undulatory extinction. Their relation to each other was then determined and plotted in a stratigraphic column. In the same column the relation of porphyry and tuff fragments to lava fragments was plotted. The resulting similarity of the two curves shows that the quartz ratio, as introduced here, can give indications about changes in the source area of graywackes.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1365-3091.1971.tb01138.x
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