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Igneous Petrology and the Nature of Magmas
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
Batholiths can be gigantic; for example, the Sierra Nevada Batholith of California, further discussed in Chapter 6, runs the entire length of the Sierra Nevada Mountains, and the Coast Range Batholith of British Columbia is even larger. Figure 5.31 shows a view of the High Sierra near Lone Pine California. The largest monolith in this photograph is Mt. Whitney, the highest peak in the Sierra Nevada Mountains. The peak left of Whitney is Keeler Needle, and left of that is Crooks Peak. All three are made of granites belonging to the Sierra Nevada Batholith.
Granite suites: a problematic concept?
Published in Australian Journal of Earth Sciences, 2020
Beyond scientific curiosity, the major reason for conducting studies of igneous petrology is to constrain the ages and compositions of the usually unexposed source rocks for the magmas, and thereby to infer their tectonic histories. Igneous rocks certainly form groups that show spatial, textural, mineralogical, chemical and isotopic similarities. These shared features suggest magma derivation from similar, perhaps related, source rocks, by similar mechanisms, and such groupings are commonly known as suites. The idea of grouping related igneous rocks into a suite has a long pedigree, extending back to Harker (1909). In most works, the term is somewhat informal and is therefore not capitalised – hence ‘suite’ rather than ‘Suite’ (see e.g. Frost et al., 2001). For example, the plutons that make up the Sierra Nevada batholith in California, are grouped into formations and those formations are grouped into what are interpreted as co-magmatic suites that are then given formal names (e.g. the Tuolumne Intrusive Suite; Bateman, 1983, 1992). In Australia, the formal use of the term ‘Suite’, with reference to granitic plutonic rocks, probably found its inspiration in the earlier work of Hine, Williams, Chappell, and White (1978) and White and Chappell (1983). It is this formal usage, and its basis, that we examine and question here.
Geology and field relations of the Wilsons Promontory batholith, Victoria: multiple, shallow-dipping, S-type, granitic sheets
Published in Australian Journal of Earth Sciences, 2018
Near-vertical, enclave-rich pipes are exposed on the west coast, intruding the MOL and the NPBM layered unit. The pipes are circular in cross-section, around 5 m across and in sharp contact with the layered NPBM. Garnet–biotite schlieren are present but not abundant. These pipes may have been local feeder conduits for NPBM magmas, which became choked with crystals and enclaves. Similar structures have been described from other batholiths, e.g. in the Sierra Nevada batholith of California (Vernon & Paterson, 2008b).