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Extraction to intrusion, Kangaroo Island, South Australia


Roberto Weinberg, Monash University, Australia




At Vivvone Bay, the evolution from melt segregation from the source, to intrustion of granites as dikes forming and linked to net veining can be followed over a short distance, including the evolution of quartz veins from the tip of the dikes.


Schematic depiction of link from extraction of magma from source to dikes and dike intrusion causing net veining.
schematic extraction of melt into dikes and intrusion
Schematic down plunge section of fold collapse and link between melt extraction in source to its intrusion through migmatites. This is mostly based on the documentation of the strucures below, and transition can take place in a few metres. Granite dykes develop net veins and some dykes can be followed into quartz veins within a couple of metres.

Photographs below illustrate the different steps depicted above.
source extraction dyke net veining
source extraction dyke net veining
Figure 3a) This photo depicts an intermediate case of layer parallel magma flow and cross-cutting dyking, possibly a case where in source melt exploits pre-existing leucosome networks to permeate the rock and is also capable of cutting across layering. Note on the upper left hand-side a coarse-grained blob feeds leucocratic (evolved) dykes that cross cut the metasedimentary host.
dyke developing quartz veins
Figure 3b) Coarse-grained dyke feeding dykelets that evolve to quartz veins at their tips on left-hand-side.
Figure 3c) Coarse-grained intrusion attempting, mostly unsuccessfully, to intrude parallel to layering giving rise to several protrusions into layers. Some protrusion develop into dykelets.