Gravity Interpretation of the Laramie Anorthosite Complex, Wyoming

Abstract

Research Article| April 01, 1973 Gravity Interpretation of the Laramie Anorthosite Complex, Wyoming D. S. HODGE; D. S. HODGE 1Department of Geological Sciences, State University of New York, Buffalo, New York 14222 Search for other works by this author on: GSW Google Scholar L. B. OWEN; L. B. OWEN 2Department of Geology, University of Wyoming, Laramie, Wyoming 82070 Search for other works by this author on: GSW Google Scholar SCOTT B. SMITHSON SCOTT B. SMITHSON 3Gravity Interpretation of the Laramie Anorthosite Complex, Wyoming Search for other works by this author on: GSW Google Scholar Author and Article Information D. S. HODGE 1Department of Geological Sciences, State University of New York, Buffalo, New York 14222 L. B. OWEN 2Department of Geology, University of Wyoming, Laramie, Wyoming 82070 SCOTT B. SMITHSON 3Gravity Interpretation of the Laramie Anorthosite Complex, Wyoming Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1973) 84 (4): 1451–1464. https://doi.org/10.1130/0016-7606(1973)84<1451:GIOTLA>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation D. S. HODGE, L. B. OWEN, SCOTT B. SMITHSON; Gravity Interpretation of the Laramie Anorthosite Complex, Wyoming. GSA Bulletin 1973;; 84 (4): 1451–1464. doi: https://doi.org/10.1130/0016-7606(1973)84<1451:GIOTLA>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 Interpretation of a gravity study of the Laramie anorthosite complex limits petrogenetic models. Bouguer gravity anomalies within the anorthosite average about −155 mgal, decrease by 12 mgal over younger granite, and increase up to 20 mgal over bordering syenite bodies. The gravity field over the anorthosite is low with respect to the metamorphic rocks on the northern border. Computed models indicate that the anorthosite mass is a plate 4 km thick with no apparent feeder pipes and is not underlain by a high-density mass. High gravity gradients and ubiquitous surface association of gravity highs over norite-syenite suggest that norite floors these syenite bodies at a depth as shallow as 0.5 km. Computed thickness of norite is about 4 km. From the gravity data, the norite-syenite seems to rim the anorthosite, except where younger intrusions may have disturbed this relation. Minimum calculated mass for respective rock types are: anorthosite, 9.7 × 1018 g; norite, 2.3 × 1018 g; syenites, 6.0 × 1017 g. The parent magma is estimated to have been of noritic anorthosite composition. Petrogenetic models derived from these data suggest that (1) in situ differentiation of gabbroic magma is unlikely, and (2) anorthosite initially differentiated from the parent magma followed by norite and syenites, then this sequence rose into the present domal configuration as a partly consolidated mush. 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.