Tectonic implications of Palaeoproterozoic post-collisional, high-K felsic igneous rocks from the Kimberley region of northwestern Australia

Abstract

Palaeoproterozoic high-K I-type granites, high-level porphyry intrusions, and felsic volcanic rocks of the Whitewater Volcanics dominate the Hooper and Lamboo Complexes in the Kimberley region of northwestern Australia. The granites, porphyries and volcanic rocks are gradational into each other in the field, and they have the same mineralogy, similar major and trace element abundances, and indistinguishable SHRIMP U–Pb zircon ages of 1865–1850 Ma. There is evidence of widespread mingling between the granites and coeval gabbros. Magma mixing may be important in the formation of some of the mafic granites, but most of the rocks probably formed from felsic parent magmas that underwent variable degrees of fractional crystallization. The felsic igneous rocks may have formed by partial melting of intermediate to felsic, calc-alkaline rocks along the southern and eastern margins of the Kimberley Craton, following accretion of various earlier Palaeoproterozoic terranes to the craton. Therefore, models for Palaeoproterozoic high-K granites in northern Australia that invoke intracratonic rifting of a stable Archaean craton may need to be revised.