Introduction (continued)

The Cretaceous Tuolumne intrusive suite (depth of emplacement: 4-8 km, Bateman 1992) comprises a normal zoning with dark, fine grained and well foliated granodiorites at the rim and light, coarse grained and weakly foliated granodiorites and granite in the centre of the pluton (Bateman and Chappel 1979, Fig. 3). However, the steeply dipping magmatic foliation generally crosscuts intraplutonic contacts and strikes perpendicular to the longaxis of this streched pluton. A contact parallel magmatic foliation was only observed within the southeastern protrusion of the pluton. The ductile host rock structures are bent into parallelism with the pluton / host rock contact at the southwestern and eastern margins of the intrusive suite. At the other contacts host rock structures are cut by the pluton (Paterson and Vernon 1995).

Figure 3. a) Simplified geologic map of the Tuolumne intrusive suite (redrawn from Paterson and Vernon 1995). b) Cross section through the Tuolumne intrusive suite along line A-B in Fig. 3a, based on data from Paterson and Vernon (1995). Colours from the legend in Fig. 3a, country rock markers as thin solid lines, magmatic foliation as thin dashed lines. Intensity of the magmatic foliation is indicated by the spacing between the lines. (Select image for enlargement)

Since all three plutons are excellent examples for CEPs both emplacement mechanism described above, including combinations of both, were proposed for their intrusion: Molyneux and Hutton (2000) proposed ballooning for the emplacement of the Ardara pluton, Bateman (1985a) suggested ballooning of a diapir for the Cannibal Creek pluton and Tikoff and Teyssier (1992) proposed dyke intrusion into a transpressional shear zone as emplacement mechanism for the Tuolumne intrusive suite. Paterson and Vernon (1995) suggested diapirism by multiple processes for all three of them.

Here, we present results of a centrifuge model simulating multiple-stage melt intrusions to study the kinematics and dynamics of CEPs. We analyse the structures observed during the experiment and compare them with those observed in the above described major natural structures to draw conclusions about emplacement of CEPs.