TY - JOUR
T1 - The source of A-type magmas in two contrasting settings
T2 - U-Pb, Lu-Hf and Re-Os isotopic constraints
AU - Pankhurst, M. J.
AU - Schaefer, B. F.
AU - Turner, S. P.
AU - Argles, T.
AU - Wade, C. E.
PY - 2013/8/2
Y1 - 2013/8/2
N2 - The sources of post-orogenic A-type magmas from two distinct geodynamic settings are compared. The end of the ca. 514-480. Ma Delamerian Orogeny, southeastern South Australia, was marked by ~. 10. Myr of bimodal A-type magmatism, driven by convective removal of thickened lithosphere. Initial Os and Hf isotope ratios record a heterogeneous lithospheric mantle source, with some input from aesthenospheric mantle. Mafic parental melts fractionated to produce the granites. In contrast, initial Os isotope ratios of the A-type magmas that comprise the ca. 1598-1583. Ma Mesoproterozoic Gawler Felsic Large Igneous Province, central South Australia, record a dominant evolved lower crust component. However, initial Hf isotope ratios from these samples are depleted, indicating a mantle source for lithophile elements. This voluminous, bimodal magmatism lasted for ~. 15. Myr, and ended the Wartakan Orogeny. In both cases the homogenisation of chemical (rheological) heterogeneities, inherited from terrain amalgamation and orogenic thickening, strengthened the lithosphere. The contemporaneous fusion of heterogeneous mantle. ±. crust may represent a common, stabilising influence on the lithospheric column regardless of tectono-magmatic setting.
AB - The sources of post-orogenic A-type magmas from two distinct geodynamic settings are compared. The end of the ca. 514-480. Ma Delamerian Orogeny, southeastern South Australia, was marked by ~. 10. Myr of bimodal A-type magmatism, driven by convective removal of thickened lithosphere. Initial Os and Hf isotope ratios record a heterogeneous lithospheric mantle source, with some input from aesthenospheric mantle. Mafic parental melts fractionated to produce the granites. In contrast, initial Os isotope ratios of the A-type magmas that comprise the ca. 1598-1583. Ma Mesoproterozoic Gawler Felsic Large Igneous Province, central South Australia, record a dominant evolved lower crust component. However, initial Hf isotope ratios from these samples are depleted, indicating a mantle source for lithophile elements. This voluminous, bimodal magmatism lasted for ~. 15. Myr, and ended the Wartakan Orogeny. In both cases the homogenisation of chemical (rheological) heterogeneities, inherited from terrain amalgamation and orogenic thickening, strengthened the lithosphere. The contemporaneous fusion of heterogeneous mantle. ±. crust may represent a common, stabilising influence on the lithospheric column regardless of tectono-magmatic setting.
UR - http://www.scopus.com/inward/record.url?scp=84879009232&partnerID=8YFLogxK
U2 - 10.1016/j.chemgeo.2013.05.010
DO - 10.1016/j.chemgeo.2013.05.010
M3 - Article
AN - SCOPUS:84879009232
VL - 351
SP - 175
EP - 194
JO - Chemical Geology
JF - Chemical Geology
SN - 0009-2541
ER -