TY - JOUR
T1 - Sillimanite and andalusite produced by base‐cation leaching and contact metamorphism of felsic igneous rocks
AU - Vernon, R. H.
AU - Flood, R. H.
AU - D'arcy, W. F.
PY - 1987
Y1 - 1987
N2 - Abstract Contact metamorphism adjacent to a porphyritic quartz‐monzodiorite at Kentucky, New South Wales, Australia has produced hornfelses in porphyritic leucogranite at a peak temperature of about 650–700° C and a maximum confining pressure of about 2 kbar (200 MPa). A gradation appears to exist from normal slightly peraluminous to modified strongly peraluminous metagranite hornfelses, which have also been enriched in sulphur. The strongly peraluminous hornfelses, containing cordierite, andalusite, sillimanite, biotite, pyrite and pyrrhotite, retain residual porphyritic igneous microstructures. These rocks appear to have been formed by leaching of base cations, during and possibly just before the contact metamorphism. Folia of fibrous sillimanite anastomose between lenticular grains of quartz and feldspar and truncate igneous zoning in plagioclase grains, suggesting that cation leaching and solution transfer occurred during growth of the sillimanite. Fibrous sillimanite also grew in grain boundaries of polygonal aggregates formed by the contact metamorphism. Therefore, at least some of the cation leaching appears to have occurred at the highest metamorphic grade. Metasandstones that are locally strongly peraluminous adjacent to the monzodiorite stock also, have probably undergone similar leaching.
AB - Abstract Contact metamorphism adjacent to a porphyritic quartz‐monzodiorite at Kentucky, New South Wales, Australia has produced hornfelses in porphyritic leucogranite at a peak temperature of about 650–700° C and a maximum confining pressure of about 2 kbar (200 MPa). A gradation appears to exist from normal slightly peraluminous to modified strongly peraluminous metagranite hornfelses, which have also been enriched in sulphur. The strongly peraluminous hornfelses, containing cordierite, andalusite, sillimanite, biotite, pyrite and pyrrhotite, retain residual porphyritic igneous microstructures. These rocks appear to have been formed by leaching of base cations, during and possibly just before the contact metamorphism. Folia of fibrous sillimanite anastomose between lenticular grains of quartz and feldspar and truncate igneous zoning in plagioclase grains, suggesting that cation leaching and solution transfer occurred during growth of the sillimanite. Fibrous sillimanite also grew in grain boundaries of polygonal aggregates formed by the contact metamorphism. Therefore, at least some of the cation leaching appears to have occurred at the highest metamorphic grade. Metasandstones that are locally strongly peraluminous adjacent to the monzodiorite stock also, have probably undergone similar leaching.
KW - base‐cation leaching
KW - contact metamorphism
KW - felsic hornfelses
KW - Key‐words: andalusite
KW - sillimanite
KW - sulphides
UR - http://www.scopus.com/inward/record.url?scp=0023467119&partnerID=8YFLogxK
U2 - 10.1111/j.1525-1314.1987.tb00395.x
DO - 10.1111/j.1525-1314.1987.tb00395.x
M3 - Article
AN - SCOPUS:0023467119
SN - 0263-4929
VL - 5
SP - 439
EP - 450
JO - Journal of Metamorphic Geology
JF - Journal of Metamorphic Geology
IS - 4
ER -