Journal of Petrology | Volume 17 | Number 4 | Pages 546-558 | 1976
© Oxford University Press 1976
research-article |
Sedimentary Structures and Magma Current Velocities in the Kalka Layered Intrusion, Central Australia
Department of Geology and Mineralogy, University of Adelaide Adelaide, South Australia, 5000
Received December 9, 1975; Revised January 27, 1976; ABSTRACT
Examples of reworked sedimentary structures (asymmetric ripple forms, planar cross-stratification, and a scour structure) and modified sedimentary structures (load casts) are described from the layered, gabbroic Kalka Intrusion in central Australia. The reworked structures are thought to be produced by the action of vigorous, unidirectional, localized currents of convectional origin. Current velocities have been estimated at between 0.001 and 5 cm sec–1 for the lower flow regime structures, and greater than 0.1 cm sec–1 for the scour structure. These compare well with theoretical convection velocities in magmas. Pyroxene/plagioclase mobility within basaltic magmas is greater than sand mobility in aqueous systems.
The advent of the current activity which produced the scour is associated with a change from discontinuous to continuous nucleation (Goode, 1976), probably due to the increased turbulence in the crystallization zone. Erosional depths within unconsolidared crystal mushes that later became anorthositic adcumulates indicate that melt diffusion can occur through at least 1 metre of cumulus aggregate.
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  C. A. Lee Post-deposition structures in the Bushveld Complex mafic sequence Journal of the Geological Society, June 1, 1981; 138(3): 327 - 341. [Abstract] [PDF]
|
|
|
|
|
|
A. N. Baxter Ultramafic and mafic nodule suites in shield-forming lavas from Mauritius Journal of the Geological Society, October 1, 1978; 135(5): 565 - 581. [Abstract] [PDF]
|
|