Journal ArticleDOI
The Importance of Residual Source Material (Restite) in Granite Petrogenesis
About:
This article is published in Journal of Petrology.The article was published on 1987-12-01. It has received 735 citations till now. The article focuses on the topics: Restite & Petrogenesis.read more
Citations
More filters
Book ChapterDOI
I- and S-type granites in the Lachlan Fold Belt
Bruce W. Chappell,A. J. R. White +1 more
Abstract: Granites and related volcanic rocks of the Lachlan Fold Belt can be grouped into suites using chemical and petrographic data. The distinctive characteristics of suites reflect source-rock features. The first-order subdivision within the suites is between those derived from igneous and from sedimentary source rocks, the I- and S-types. Differences between the two types of source rocks and their derived granites are due to the sedimentary source material having been previously weathered at the Earth's surface. Chemically, the S-type granites are lower in Na, Ca, Sr and Fe3+/Fe2+, and higher in Cr and Ni. As a consequence, the S-types are always peraluminous and contain Al-rich minerals. A little over 50% of the I-type granites are metaluminous and these more mafic rocks contain hornblende. In the absence of associated mafic rocks, the more felsic and slightly peraluminous I-type granites may be difficult to distinguish from felsic S-type granites. This overlap in composition is to be expected and results from the restricted chemical composition of the lowest temperature felsic melts. The compositions of more mafic I- and S-type granites diverge, as a result of the incorporation of more mafic components from the source, either as restite or a component of higher temperature melt. There is no overlap in composition between the most mafic I- and S-type granites, whose compositions are closest to those of their respective source rocks. Likewise, the enclaves present in the more mafic granites have compositions reflecting those of their host rocks, and probably in most cases, the source rocks.S-type granites have higher δ18O values and more evolved Sr and Nd isotopic compositions, although the radiogenic isotope compositions overlap with I-types. Although the isotopic compositions lie close to a mixing curve, it is thought that the amount of mixing in the source rocks was restricted, and occurred prior to partial melting. I-type granites are thought to have been derived from deep crust formed by underplating and thus are infracrustal, in contrast to the supracrustal S-type source rocks.Crystallisation of feldspars from felsic granite melts leads to distinctive changes in the trace element compositions of more evolved I- and S-type granites. Most notably, P increases in abundance with fractionation of crystals from the more strongly peraluminous S-type felsic melts, while it decreases in abundance in the analogous, but weakly peraluminous, I-type melts.
Journal ArticleDOI
A review of the relationships between granitoid types, their origins and their geodynamic environments
TL;DR: Granitoids are divided into several types according to their mineral assemblages, their field and petrographical features, and their chemical and isotopic characteristics.
Journal ArticleDOI
Two contrasting granite types: 25 years later
Bruce W. Chappell,A. J. R. White +1 more
TL;DR: The concept of I• and S•type granites was introduced in 1974 to account for the observation that, apart from the most felsic rocks, the granites in the Lachlan Fold Belt have properties that generally fall into two distinct groups as mentioned in this paper.
Journal ArticleDOI
A-type granites and related rocks: Evolution of a concept, problems and prospects
TL;DR: A-type granites have long been recognized as a distinct group of granites, the term A-type was coined first less than thirty years ago as discussed by the authors, and they are fairly common at shallower depths, especially at the subvolcanic level where they form ring complexes rooting caldera volcanoes.
Journal ArticleDOI
Aluminium saturation in I- and S-type granites and the characterization of fractionated haplogranites
TL;DR: In an unfractionated state, there are some overlaps in the degree of Al saturation in these mafic granites produced by partial melting as mentioned in this paper, but when extended fractional crystallization of these felsic partial melts took place, an almost complete separation in Al-saturation developed between I-type and more peraluminous S-type melts.
Related Papers (5)
Zircon saturation revisited: temperature and composition effects in a variety of crustal magma types
E. Bruce Watson,T. Mark Harrison +1 more