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Construction of a pluton: Evidence from an exposed cross section of the Searchlight pluton, Eldorado Mountains, Nevada

2001; Geological Society of America; Volume: 113; Issue: 9 Linguagem: Inglês

10.1130/0016-7606(2001)113 2.0.co;2

1943-2674

Carolyn A. Bachl, Calvin F. Miller, Jonathan S. Miller, James E. Faulds,

Atmospheric and Environmental Gas Dynamics

Research Article| September 01, 2001 Construction of a pluton: Evidence from an exposed cross section of the Searchlight pluton, Eldorado Mountains, Nevada Carolyn A. Bachl; Carolyn A. Bachl 1Department of Geology, Vanderbilt University, Nashville, Tennessee 37235, USA Search for other works by this author on: GSW Google Scholar Calvin F. Miller; Calvin F. Miller 1Department of Geology, Vanderbilt University, Nashville, Tennessee 37235, USA Search for other works by this author on: GSW Google Scholar Jonathan S. Miller; Jonathan S. Miller 2Department of Geology, San Jose State University, San Jose, California 95192-0102, USA Search for other works by this author on: GSW Google Scholar James E. Faulds James E. Faulds 3Nevada Bureau of Mines and Geology, University of Nevada, Reno, Nevada 89557, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Carolyn A. Bachl 1Department of Geology, Vanderbilt University, Nashville, Tennessee 37235, USA Calvin F. Miller 1Department of Geology, Vanderbilt University, Nashville, Tennessee 37235, USA Jonathan S. Miller 2Department of Geology, San Jose State University, San Jose, California 95192-0102, USA James E. Faulds 3Nevada Bureau of Mines and Geology, University of Nevada, Reno, Nevada 89557, USA Publisher: Geological Society of America Received: 24 Feb 2000 Revision Received: 11 Sep 2000 Accepted: 07 Mar 2001 First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (2001) 113 (9): 1213–1228. https://doi.org/10.1130/0016-7606(2001)113 2.0.CO;2 Article history Received: 24 Feb 2000 Revision Received: 11 Sep 2000 Accepted: 07 Mar 2001 First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Carolyn A. Bachl, Calvin F. Miller, Jonathan S. Miller, James E. Faulds; Construction of a pluton: Evidence from an exposed cross section of the Searchlight pluton, Eldorado Mountains, Nevada. GSA Bulletin 2001;; 113 (9): 1213–1228. doi: https://doi.org/10.1130/0016-7606(2001)113 2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract A top-to-bottom cross section of the Searchlight pluton is exposed in a large tilt block in the Colorado River extensional corridor of southern Nevada. Hornblende barometry and geologic relations indicate that the pluton was about 10 km thick, extending from approximately 3 to 13 km depth. The pluton is stratified with about 2 km of fine-grained quartz monzonite below the roof, 2 km of granite in the center, and 6 km of coarser, more mafic quartz monzonite at the bottom. The lower unit has a pronounced magmatic foliation that was subhorizontal prior to tilting. Contacts between the units are gradational over a few centimeters to about 20 m. Geometry, field relations, and elemental and isotopic data suggest that the three units mark the terminal stages of evolution of magma that filled a very thick magma chamber. The upper unit formed as a solidification front that migrated downward from the roof, and the middle unit granite and the lower unit represent complementary segregated melt and crystal-rich cumulate. Thus, the dominant part of the pluton appears to have solidified in monotonic fashion from more or less uniform magma that was compositionally similar to the upper unit.The basal quartz monzonite and the lower part of the granite enclose widely scattered, synplutonic hornblende gabbro and diorite pods that range from centimeter to kilometer scale. These rocks are commonly fine grained and formed as quenched mafic melts. They are isotopically distinct from the main sequence and represent discrete injections into the magma chamber. The mafic magmas were contaminated by, but did not strongly affect, the main-sequence magma.The Nd and Sr isotopic compositions of the main-sequence magma are intermediate between those of regional crust and enriched mantle-derived basalts like those represented by the mafic pods. This suggests that the principal magma was a hybrid with about 60% mantle component, and thus the pluton represents both addition to and internal reorganization of the crust You do not have access to this content, please speak to your institutional administrator if you feel you should have access.