TY - JOUR
T1 - Volcanism of shoshonite to high-K andesite affinity in an Archean arc environment, Oxford Lake, Manitoba
AU - Brooks, C.
AU - Ludden, J.
AU - Pigeon, Y.
AU - Hubregtse, J. J. M. W.
PY - 1982
Y1 - 1982
N2 - Volcanic rocks of the Archean Oxford Lake Group are characterized by a stratigraphic progression from mafic to felsic compositions, accompanied by a systematic decrease in incompatible element abundances. This, coupled with high abundances of Sr, Rb, K2O, and La, high (La/Yb)n, and unfractionated (flat to concave) heavy-REE (rare earth element) profiles, distinguishes these rocks as an Archean shoshonite to high-K andesite-dacite-rhyolite series, directly comparable to modern analogues formed in convergent tectonic settings. The trace-element data support a model of petrogenesis in which an Archean mantle source region was modified by volatiles rich in large-ion-lithophile elements, the modified mantle was subjected to partial melting forming a parental liquid of shoshonitic character, and this liquid principally underwent amphibole fractionation to form the evolved rock compositions. This process is envisaged as terminal magmatism during the final (senile) stage of activity in an arc setting. The Rb/Sr age (2650+ or -80Ma) and initial-Sr ratio (0.70145+ or -38) of the Oxford Lake Group are in accord with this model; when coupled with the 2.7Ga age for the underlying Hayes River Group volcanics, these data indicate a short interval (<50Ma?) for Archean crustal development in the area.
AB - Volcanic rocks of the Archean Oxford Lake Group are characterized by a stratigraphic progression from mafic to felsic compositions, accompanied by a systematic decrease in incompatible element abundances. This, coupled with high abundances of Sr, Rb, K2O, and La, high (La/Yb)n, and unfractionated (flat to concave) heavy-REE (rare earth element) profiles, distinguishes these rocks as an Archean shoshonite to high-K andesite-dacite-rhyolite series, directly comparable to modern analogues formed in convergent tectonic settings. The trace-element data support a model of petrogenesis in which an Archean mantle source region was modified by volatiles rich in large-ion-lithophile elements, the modified mantle was subjected to partial melting forming a parental liquid of shoshonitic character, and this liquid principally underwent amphibole fractionation to form the evolved rock compositions. This process is envisaged as terminal magmatism during the final (senile) stage of activity in an arc setting. The Rb/Sr age (2650+ or -80Ma) and initial-Sr ratio (0.70145+ or -38) of the Oxford Lake Group are in accord with this model; when coupled with the 2.7Ga age for the underlying Hayes River Group volcanics, these data indicate a short interval (<50Ma?) for Archean crustal development in the area.
UR - http://www.scopus.com/inward/record.url?scp=0019998981&partnerID=8YFLogxK
U2 - 10.1139/e82-005
DO - 10.1139/e82-005
M3 - Article
AN - SCOPUS:0019998981
SN - 0008-4077
VL - 19
SP - 55
EP - 67
JO - Canadian Journal of Earth Sciences
JF - Canadian Journal of Earth Sciences
IS - 1
ER -