Portal de Periódicos da CAPES

PRECAMBRIAN MONAZITE AND ZIRCON FROM THE MOUNTAIN PASS RARE-EARTH DISTRICT, SAN BERNARDINO COUNTY, CALIFORNIA

1955; Geological Society of America; Volume: 66; Issue: 10 Linguagem: Inglês

10.1130/0016-7606(1955)66[1247

1943-2674

Howard W. Jaffe,

Mineralogy and Gemology Studies

Research Article| October 01, 1955 PRECAMBRIAN MONAZITE AND ZIRCON FROM THE MOUNTAIN PASS RARE-EARTH DISTRICT, SAN BERNARDINO COUNTY, CALIFORNIA HOWARD W JAFFE HOWARD W JAFFE U. S, GEOLOGICAL SURVEY, GEOCHEMISTRY AND PETROLOGY BRANCH, WASHINGTON 25, D. C. Search for other works by this author on: GSW Google Scholar Author and Article Information HOWARD W JAFFE U. S, GEOLOGICAL SURVEY, GEOCHEMISTRY AND PETROLOGY BRANCH, WASHINGTON 25, D. C. Publisher: Geological Society of America Received: 27 Jan 1955 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1955, 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 (1955) 66 (10): 1247–1256. https://doi.org/10.1130/0016-7606(1955)66[1247:PMAZFT]2.0.CO;2 Article history Received: 27 Jan 1955 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 HOWARD W JAFFE; PRECAMBRIAN MONAZITE AND ZIRCON FROM THE MOUNTAIN PASS RARE-EARTH DISTRICT, SAN BERNARDINO COUNTY, CALIFORNIA. GSA Bulletin 1955;; 66 (10): 1247–1256. doi: https://doi.org/10.1130/0016-7606(1955)66[1247:PMAZFT]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 Age determinations were made of three monazite samples from carbonate rock and four zircon samples from the associated shonkinite of the Mountain Pass district, San Bernardino County, California. The determinations made by the alpha-counting and total-lead method gave an average age of 950 million years for monazite and 840 million years for zircon. One of the monazite samples contains 2.65 per cent thorium, 0.002 per cent uranium, and 0.1130 per cent lead, giving a maximum age of 955 million years uncorrected for original lead. The Pb208/Th232 age of this monazite is 925 million years, based on an isotopic analysis of the monazite lead corrected for original lead by an isotopic analysis of galena lead from the same deposit. The monazite lead is 98.854 per cent radiogenic of which 98.342 per cent is Pb208 and 0.512 per cent is Pb206. The isotopic composition of the galena lead is similar to that of Precambrian galena from other localities.Optical properties of the monazite are: α = 1.779, β = 1.781, γ = 1.833, 2V (calc.) = 26° (+), r < υ, Z Λ c = 7°, and Y = b. The density measured on the Berman microbalance is 4.98; the density calculated from the rule of Gladstone and Dale, n – 1/d = K, is 5.03. Other data include spectrographic and chemical analyses of the monazite. 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.