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Petrologic and Rb-Sr Isotopic Study of the Chiquimula Pluton, Southeastern Guatemala

1971; Geological Society of America; Volume: 82; Issue: 10 Linguagem: Inglês

10.1130/0016-7606(1971)82[2729

1943-2674

Russell E. Clemons, Leon E. Long,

Geological and Tectonic Studies in Latin America

Research Article| October 01, 1971 Petrologic and Rb-Sr Isotopic Study of the Chiquimula Pluton, Southeastern Guatemala RUSSELL E CLEMONS; RUSSELL E CLEMONS Department of Earth Sciences, New Mexico State University, Las Cruces, New Mexico 88001 Search for other works by this author on: GSW Google Scholar LEON E LONG LEON E LONG Department of Geological Sciences, University of Texas at Austin, Austin, Texas 78712 Search for other works by this author on: GSW Google Scholar Author and Article Information RUSSELL E CLEMONS Department of Earth Sciences, New Mexico State University, Las Cruces, New Mexico 88001 LEON E LONG Department of Geological Sciences, University of Texas at Austin, Austin, Texas 78712 Publisher: Geological Society of America Received: 05 Oct 1970 Revision Received: 22 Apr 1971 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1971, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1971) 82 (10): 2729–2740. https://doi.org/10.1130/0016-7606(1971)82[2729:PARISO]2.0.CO;2 Article history Received: 05 Oct 1970 Revision Received: 22 Apr 1971 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation RUSSELL E CLEMONS, LEON E LONG; Petrologic and Rb-Sr Isotopic Study of the Chiquimula Pluton, Southeastern Guatemala. GSA Bulletin 1971;; 82 (10): 2729–2740. doi: https://doi.org/10.1130/0016-7606(1971)82[2729:PARISO]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 The Chiquimula pluton is one of a chain of plutons that extends across southern Guatemala and northern Honduras. Its exposed area of about 300 sq km in southeastern Guatemala is highly irregular. Exposed parts of the epizonal pluton are dominantly granodiorite; gabbro may be abundant, but it is exposed only in the deepest canyons. Diorite is predominant along the southern and western margins, and the rock is an intergrading mixture of granodiorite with subordinate adamellite and granite near the northern and eastern margins.A whole-rock Rb-Sr isochron diagram shows data points falling in two distinct groups. Granite and adamellite form a scattering of points indicating relatively high Rb/Sr (3.3 to 4.6) and high Sr87/Sr86 (0.72 to 0.75). Points from the volumetrically more important gabbro and grand diorite, indicative of low Rb/Sr (1.2 or less) and Sr87/Sr86 (0.706 to 0.708), form a well-defined isochron corresponding to an age of 50 ± 5 m.y. and initial Sr87/Sr86 = 0.7060 ± 0.0002. K-Ar and Rb-Sr biotite ages from granite of 84 m.y. and 95 m.y., respectively, are younger than the whole-rock Rb-Sr age (215 m.y.) of the same specimen, but older than the age of emplacement of the pluton as suggested by the whole-rock isochron from granodiorite and gabbro.Field relations, petrographic data, and isotopic data are consistent with the interpretation that the Chiquimula pluton is just beginning to be unroofed. The compositional variation probably resulted from a combination of assimilation and differentiation of a granodioritic magma. The more granitic parts may be due to partially assimilated more siliceous exotic blocks of basement rock. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.