Contacts can be combinations of… Injection Deformation Melting/in situ reactions Things to consider on Wednesday!
Dome & keel structures in the Barberton granitoid-greenstone terrain Domes: 3.4 & 3.2 Ga gneissic TTG`s Concentric foliation patterns concordant with foliation in the surrounding supracrustals Keels: tightly folded synformal supracrustals with TPC`s. After Anhaeusser et al. (1981) Anhaeusser (2001). 5 km N
Table 18-1. Didier, J. and Barbarin (1991) The different type of enclaves in granites: Nomenclature. In J. Didier and B. Barbarin (1991) (eds.), Enclaves in Granite Petrology. Elsevier. Amsterdam, pp. 19-23.
Try to sketh two different contacts: A shallow intrusive, emplaced in a low strain situation A deep intrusive, syntectonic
Batholiths Plutons associations Definition not too clear Old litterature: « primordial » granitic level, somewhere down. Modern conceptions: associations of individual plutons, each with its shape and structures Probably rather flat as well!
Figure 4-20. Schematic block diagram of some intrusive bodies. “Vertical” intrusions
An “old” view of a batholith Figure 17-16. Schematic cross section of the Coastal batholith of Peru. The shallow flat-topped and steep- sided “bell-jar”-shaped plutons are stoped into place. Successive pulses may be nested at a single locality. The heavy line is the present erosion surface. From Myers (1975) Geol. Soc. Amer. Bull., 86, 1209-1220.
Figure 4-36. Diagrammatic cross section of the Boulder Batholith, Montana, prior to exposure. After Hamilton and Myers (1967), The nature of batholiths. USGS Prof. Paper, 554-C, c1-c30. Modern conceptions: flat batholiths