High Heat Production Granites: their origin and significance in crustal evolution

Project Details

Fields of Research

• Igneous geology
• Petrogenesis
• Isotope geochemistry
• Geochronology

Description

High Heat Production Granites (HHPG) have elevated concentrations of K 2 O, Rb, LREE, U and Th and produce anomalous radiogenic heat when compared with upper crustal averages. Granites of this type are sometimes referred to as A-types, anorogenic granites, alkalic granites or Rapakevi granites. They are distributed through geological time but in Australia they appear to have a particular concentration in the Palaeoproterozoic and early Mesoproterozoic.

These granitic rocks are important because they provide anomalous sources of present-day intra-crustal heating and are potential dry geothermal energy sources. They were also very important in their host terrains at the time of their intrusion because of their association with regional zones of anomalous mid- to upper-crustal heating and metamorphism, and because they are a principle vector in the crustal differentiation of heat production. The anomalous thermal regimes associated with these granites appear to have a profound influence on the strength and deformation history of the contemporary continental crust.

A key question is what are the sources of these granites and particularly what is the source of their anomalous U- and Th-contents? Is their source within the crust or in the upper mantle? Did that source have a prolonged prior history of U- and Th-enrichment?

The objective of this project will be to comprehensively characterise the mineralogy, geochemistry and isotopic compositions of the HHPG suites from Australian Proterozoic terrains and to determine their sources and to model their petrogenesis. A key tool in this research will be the use of U-Pb and Sm-Nd isotope systematics in order to date the granitic source regions. The project will work on samples from widely distributed terrains but will also involve some detailed fieldwork classic occurrences of this suite. This will probably be undertaken in the Reynolds Range area in the western Arunta Inlier.

Supervisors