Searchlight pluton, a steeply tilted, 10 km thick Miocene intrusion in southern Nevada, exposes a zone with abundant, 5-400 m long blocks of Proterozoic gneiss. Blocks are present within a pair of subparallel horizons that make up a 2 km thick zone and extend 5 km laterally away from the plutons N-margin, slightly oblique to the initially subhorizontal boundary between the pluton's middle granite and lower quartz monzonite units. Blocks are commonly polylithologic and well foliated, with long and intermediate dimensions parallel to their own foliation, the foliation of the host granitoid, and the orientation of flattened magmatic enclaves. Blocks have a sub-angular tabular geometry with an average aspect ratio of ~3.7. We interpret the blocks as stoped and emplaced after repeated wall collapse events onto a crystal-rich mush and transported laterally primarily by matrix-supported debris flows. SHRIMP ages of granitoid zircons constrain block emplacement between ~16.1-16.3 Ma, a small fraction of the lifetime of the pluton (15.8-17.7 Ma). Though blocks are locally abundant (~20% exposure over ~0.3 km2), they constitute <1% of the entire exposure, suggesting that stoping played a minor role in the emplacement process. LA-ICPMS analysis of zircons from host granitoids suggest minor host contamination by block disaggregation - a sample adjacent (15 cm) to a block contained ~8 % inherited Proterozoic zircons, while samples from elsewhere in the pluton yielded <<1%.
Scaled settling experiments suggest tabular blocks deposit with their long and intermediate axes parallel to surfaces; blocks with a geometry controlled by foliation would on average possess a subparallel alignment of both their geometric shape and foliation. Experiments also show that fluid sublayers may become trapped beneath blocks and allow lateral transport by hydroplaning.
| Identifer | oai:union.ndltd.org:VANDERBILT/oai:VANDERBILTETD:etd-07282006-152403 |
| Date | 03 August 2006 |
| Creators | Perrault, Daniel Scott |
| Contributors | Dr. Calvin Miller, Dr. David Furbish |
| Publisher | VANDERBILT |
| Source Sets | Vanderbilt University Theses |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.vanderbilt.edu/available/etd-07282006-152403/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to Vanderbilt University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
Page generated in 0.0016 seconds