Bradley S. Van Gosen
20201215
Whole-rock geochemical data for alkaline intrusive rocks in the Wet Mountains area of Custer and Fremont Counties, south-central Colorado, USA
tabular digital data; a CSV format file
Denver, CO
U.S. Geological Survey
Additional information about Originators: Van Gosen, Bradley S., https://orcid.org/0000-0003-4214-3811
Suggested citation: Van Gosen, B.S., 2020, Whole-rock geochemical data for alkaline intrusive rocks in the Wet Mountains area of Custer and Fremont Counties, south-central Colorado, USA: U.S. Geological Survey data release, https://doi.org/10.5066/P99YBJLX
https://doi.org/10.5066/P99YBJLX
This data release contains the whole-rock major and trace element analyses of 51 samples of intrusive igneous rocks from the Wet Mountains area of Custer and Fremont counties of south-central Colorado, collected by U.S. Geological Survey (USGS) geologists.
The samples were collected from breccias, veins and thin dikes, and a variety of carbonatite, felsic, mafic, and ultramafic intrusions across the area. The first 41 samples listed in this data release were collected in July 2007, originally as part of a reconnaissance study of the thorium deposits of the area (Van Gosen and others, 2009). The samples are grab samples from outcrops, shallow open-pit excavations, and mineral prospect trenches. The last 10 samples listed in this data release were originally collected and geochemically analyzed in 1976 as part of a USGS study of carbonatites in this area (Armbrustmacher, 1976, 1979; Armbrustmacher and Brownfield, 1978). These 10 carbonatite samples were reanalyzed by modern analytical methods in 2007, and the new data are included in this data release.
The Wet Mountains area hosts a variety of alkaline intrusions (Armbrustmacher, 1984), which includes three Cambrian-age alkaline complexes (Olson and others, 1977) that intruded the surrounding Precambrian terrane. These are (1) the McClure Mountain Complex (Shawe and Parker, 1967; Armbrustmacher, 1984), (2) the Gem Park Complex (Parker and Sharp, 1970), and (3) the complex at Democrat Creek (Armbrustmacher, 1984). In the Wet Mountains area, elevated concentrations of thorium and rare earth elements (REEs) occur in veins, syenite dikes, fracture zones, breccias, and carbonatite dikes (Armbrustmacher, 1988). These thorium-REE deposits are distal to the alkaline complexes but are thought to be genetically associated.
Characteristics of the thorium and REE deposits in the area, as well as typical concentrations and resource estimates, are detailed in the publications listed in the supplementary file “Wet Mountains area publications.pdf”. Armbrustmacher (1988) determined that vein and fracture zone deposits contain most of the thorium and REE resources in the area. These are linear features, typically 1–2 meters thick, but a few are as much as 15 meters thick. Some individual thorium veins can be traced in outcrop for 1,500 m and some radioactive fracture zones for as much as 13 kilometers. Most of these vein- and fracture-zone deposits occur within a 57 square kilometers tract of Precambrian gneiss and migmatite (Scott and others, 1976) located south and southeast of the quartz syenite complex at Democrat Creek; in this area Christman and others (1953, 1959) mapped nearly 400 veins.
Most of the samples in this data release are examples of unaltered alkaline igneous rocks of the intrusive complexes rather than the mineral deposits. These samples were selected in the field to study possible relationships between the magmatic complexes and the thorium-REE deposits.
All samples included in this data release were analyzed by laboratories contracted by the USGS. Major and trace element concentrations were determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES) and inductively coupled plasma-mass spectrometry (ICP-MS). An acceptable criteria for the data has been identified based on (1) if recovery of each element is within a designated percentage at five times the lower limit of determination, and (2) the calculated relative standard deviation of duplicate samples is no greater than that percentage. The reported laboratory percentages for the acceptance criteria are +/- 15 percent for ICP-AES and ICP-MS. Ten carbonatite samples were additionally analyzed by wavelength dispersive X-ray fluorescence (WDXRF) to determine the concentrations of major elements as oxides. The reported laboratory percentages for the acceptance criteria are +/- 5 percent for WDXRF.
Data are reported in a comma-separated values (CSV) file that lists the samples that were analyzed, latitude/longitude location information, brief sample descriptions, and relevant publications. The column headings and abbreviations are explained in the accompanying data dictionary.
References cited above:
Armbrustmacher, T. J., 1976, Thorium deposits in the Wet Mountains area, Fremont and Custer Counties, Colorado: U.S. Geological Survey Open-File Report 76–284, 18 p.,
https://doi.org/10.3133/ofr76284
Armbrustmacher, T.J., 1979, Replacement and primary magmatic carbonatites from the Wet Mountains area, Fremont and Custer Counties, Colorado: Economic Geology, v. 74, no. 4, p. 888–901, http://doi.org/10.2113/gsecongeo.74.4.888
Armbrustmacher, T.J., 1984, Alkaline rock complexes in the Wet Mountains area, Custer and Fremont Counties, Colorado: U.S. Geological Survey Professional Paper 1269, 33 p., https://doi.org/10.3133/pp1269
Armbrustmacher, T.J., 1988, Geology and resources of thorium and associated elements in the Wet Mountains area, Fremont and Custer Counties, Colorado: U.S. Geological Survey Professional Paper 1049–F, 34 p., 1 plate, https://doi.org/10.3133/pp1049f
Armbrustmacher, T.J., and Brownfield, I.K., 1978, Carbonatites in the Wet Mountains area, Custer and Fremont Counties, Colorado—Chemical and mineralogical data: U.S. Geological Survey Open-File Report 78–177, 6 p., 3 sheets, https://doi.org/10.3133/ofr78177
Christman, R.A., Brock, M.R., Pearson, R.C., and Singewald, Q.D., 1959, Geology and thorium deposits of the Wet Mountains, Colorado—A progress report: U.S. Geological Survey Bulletin 1072–H, p. 491–535, https://doi.org/10.3133/b1072h
Christman, R.A., Heyman, A.M., Dellwig, L.F., and Gott, G.B., 1953, Thorium investigations 1950–52, Wet Mountains, Colorado: U.S. Geological Survey Circular 290, 40 p., 5 plates, https://doi.org/10.3133/cir290
Olson, J.C., Marvin, R.F., Parker, R.L., and Mehnert, H.H., 1977, Age and tectonic setting of lower Paleozoic alkalic and mafic rocks, carbonatites, and thorium veins in southcentral Colorado: U.S. Geological Survey Journal of Research, v. 5, no. 6, p. 673–687, https://doi.org/10.3133/70007423
Parker, R.L., and Sharp, W.N., 1970, Mafic-ultramafic igneous rocks and associated carbonatites of the Gem Park Complex, Custer and Fremont Counties, Colorado: U.S. Geological Survey Professional Paper 649, 24 p., https://doi.org/10.3133/pp649
Scott, G. R., Taylor, R. B., Epis, R. C., and Wobus, R. A., 1976, Geologic map of the Pueblo 1°x2° quadrangle, south-central Colorado: U.S. Geological Survey Miscellaneous Field Studies Map MF–775, scale 1:250,000, https://doi.org/10.3133/mf775
Shawe, D.R., and Parker, R.L., 1967, Mafic-ultramafic layered intrusion at Iron Mountain, Fremont County, Colorado: U.S. Geological Survey Bulletin 1251–A, 28 p., https://doi.org/10.3133/b1251A
Van Gosen, B.S., Gillerman, V.S., and Armbrustmacher, T.J., 2009, Thorium deposits of the United States—Energy resources for the future?: U.S. Geological Survey Circular 1336, 21 p., https://doi.org/10.3133/cir1336
This data release presents a compilation of results of geochemical analyses of a suite of rock samples collected by USGS geologists in the Wet Mountains area of south-central Colorado. This area hosts numerous occurrences of thorium and earth element (REE) concentrations, which are along fractures and in thin felsic veins, carbonatite dikes, and breccias. The purpose of this sampling was to gather geochemical information on intrusive rocks that may be genetically related to the REE-thorium mineralization across the area, as well as examine the concentrations of the REEs and thorium in various geologic settings using modern geochemical analytical techniques. These data are made available for use in geologic, exploration, and environmental background studies.
The geochemical data provided in this data release contain trailing digits. If the CSV files are opened directly in Microsoft Excel, data values may be truncated. To ensure the appropriate number of decimal places are displayed when using Excel, please open a blank workbook and import the data from the CSV files as text (no data type detection).
1976
2007
Sample collection and analysis period
Not planned
-105.55257
-105.35500
38.52419
38.22300
ISO 19115 Topic Category
geoscientificinformation
USGS Thesaurus
geology
economic geology
metallic mineral resources
mineral resources
geochemistry
mass spectroscopy
none
Department of the Interior
DOI
U.S. Geological Survey
USGS
Energy and Minerals Mission Area
Mineral Resources Program
MRP
Region 7: Upper Colorado Basin
Geology, Geophysics, and Geochemistry Science Center
GGGSC
Inductively Coupled Plasma-Atomic Emission Spectrometry
ICP-AES
Inductively Coupled Plasma-Mass Spectrometry
ICP-MS
Wavelength Dispersive X-Ray Fluorescence Spectrometry
WDXRF
rare earth elements
thorium
data release
USGS Metadata Identifier
USGS:5fa5aee1d34ed3698f92dfcc
Geographic Names Information System (GNIS)
Custer County
Fremont County
Wet Mountains
McClure Mountain
Gem Park
Iron Mountain
Democrat Creek
Common Geographic Areas
United States of America
USA
Colorado
south-central Colorado
Geolex
McClure Mountain Complex
Gem Park Complex
Democrat Creek complex
Geolex
Precambrian
Cambrian
None. Please see 'Distribution Info' for details
Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although these data have been processed successfully on a computer system at the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty. The USGS or the U.S. Government shall not be held liable for improper or incorrect use of the data described and/or contained herein.
Bradley S Van Gosen
U.S. Geological Survey
mailing
Mail Stop 973, PO Box 25046
Denver
CO
80225
USA
303-236-1566
bvangose@usgs.gov
The release of this dataset was funded by the U.S. Geological Survey Mineral Resources Program (MRP).
Environment as of Metadata Creation: Microsoft [Unknown] Version 6.2 (Build 9200); Esri ArcGIS 10.8.1 (Build 4959) Service Pack N/A (Build N/A)
The chemical data of this data set represent analyses of rock samples collected in support of mineral deposit research projects of the U.S. Geological Survey (USGS). Attribute fields and values were reviewed and checked for accuracy and consistency of terms.
This data set was derived from rock samples collected by U.S. Geological Survey (USGS) geologists and chemically analyzed by laboratories contracted by the USGS. The samples in this data set were collected for the purpose of trace elements and whole-rock major analysis. The samples have been analyzed using documented techniques.
This data set provides the chemical analyses of 51 rock samples for 57 elements, including Ag, Al, As, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cs, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Ho, In, K, La, Li, Lu, Mg, Mn, Mo, Na, Nb, Nd, Ni, P, Pb, Pr, Rb, Sb, Sc, Si, Sm, Sn, Sr, Ta, Tb, Th, Ti, Tl, Tm, U, V, W, Y, Yb, Zn, and Zr. The data set provides brief descriptive information for each sample.
Coordinates: Sample locations were recorded using a hand-held GPS receiver using the WGS84 datum. The location determined by GPS should be accurate to the nearest latitude or longitude second, or accurate within the nearest 10,000th of a degree latitude (11 meters) or longitude (8.7 meters). Locations for the Star and Flying Y carbonatites are approximate, calculated from Figure 1 of Armbrustmacher and Brownfield (1978).
No formal vertical (elevation) accuracy tests were conducted.
The last ten samples listed in the data set (which have Field_ID values that begin with 76A) were collected circa 1976 by USGS geologist T.J. Armbrustmacher, collected as hand samples of outcrops of carbonatite intrusions. Archived publverized splits of these ten samples were reanalyzed in 2008 by a commercial laboratory contracted by the U.S. Geological Survey (USGS). These 10 samples were analyzed by inductively coupled plasma-atomic emission spectrometry (ICP-AES) and inductively coupled plasma-mass spectrometry (ICP-MS) to determine the concetrations of 55 major and trace elements, and also analyzed by wavelength dispersive x-ray fluorescence spectrometry (WDXRF) to determine the concentrations of 11 major elements (methods described below).
The first 40 samples in the data set were collected by USGS geologist Bradley S. Van Gosen, collected as hand samples of outcrops or exposures in exploration trenches. These samples were analyzed in 2007 by a commercial laboratory contracted by the USGS, also by ICP-AES and ICP-MS.
Analytical data associated with these samples were derived using the following criteria: 1) Each analytical determination must be linked to a valid and unique sample lab number; and 2) each analytical determination must be identified by analyte.
Upon completion of the chemical analysis, a quality control analysis of the results was conducted by USGS personnel. The final, approved data were stored in the Oracle-based National Geochemical Database (NGDB) maintained by the USGS.
Details of the analtyical techniques are as follows:
Fifty-five major (except Si and Na) and trace elements were determined by ICP-AES and ICP-MS. One-tenth of a gram of sample was decomposed using a sodium peroxide sinter at 450°C. The resultant cake was leached with water and acidified with nitric acid. After an addition of tartaric acid, aliquots of the digested sample were aspirated into the ICP-AES and the ICP-MS. The concentrations of the optimal elements from the ICP-AES and ICP-MS were determined. Calibration on the ICP-AES was performed by standardizing with digested rock reference materials and a series of multi-element solution standards. The ICP-MS was calibrated with aqueous standards. Internal standards were used to compensate for matrix affects and internal drifts. Analytical Performance: Data were deemed acceptable if recovery for elements was +/- 15 percent at five times the limit of detection and the calculated relative standard deviation of duplicate sample was no greater than 15 percent.
Eleven major elements (Al2O3; CaO; Cr2O3; Fe2O3; K2O; MgO; MnO; Na2O; P2O5; SiO2; TiO2), as well as loss on ignition (LOI) at 1000°C, were determined by WDXRF. Sample material was roasted at 1000°C for 1 hour in order to determine LOI. Dried sample material was mixed with a lithium tetraborate/lithium metaborate/LiBr flux and placed into a platinum crucible. The sample was loaded into the automated claisse fluxer and samples were fused at 1100°C. Fused discs were analyzed using WDXRF. The disc was irradiated by a rhodium x-ray tube. X-ray photons emitted by the elements in the sample were counted and concentrations determined using previously prepared calibration curves. Calibration curves for each element were derived from a variety of international reference materials and a number of synthetic standards to extend the range for certain elements. The standards covered a wide range of geological materials, biased towards igneous rock types. Analytical Performance: Data were deemed acceptable if recovery for analytes was +/- 5 percent at five times the limit of detection and the calculated relative standard deviation of duplicate samples was no greater than 5 percent.
20200510
Point
0.00001
0.00001
Decimal degrees
D_WGS_1984
WGS_1984
6378137.0
298.257223563
Wet_Mountains_area_intrusive_rock_chemistry.csv [.xls]
Table of descriptive attributes and geochemical analyses of rock samples from the Wet Mountains area of south-central Colorado.
U.S. Geological Survey
Wet_Mountains_area_intrusive_rock_chemistry_DataDictionary.csv contains descriptions for the attributes and column headers in the csv datafile, Wet_Mountains_area_intrusive_rock_chemistry.csv.
Wet_Mountains_area_intrusive_rock_chemistry_DataDictionary.csv (https://doi.org/10.5066/P99YBJLX)
Wet_Mountains area publications.pdf contains a bibliography of publications that describe the igneous intrusions and associated REE-thorium occurrences in the Wet Mountains area. This file is readable in Adobe Acrobat.
Wet_Mountains area publications.pdf
Wet_Mountains_area_intrusive_rock_chemistry_sample_sites.shp is an ArcGIS shapefile that can be used to plot the locations of the samples included in this dataset.
Wet_Mountains_area_intrusive_rock_chemistry_sample_sites.shp
U.S.Geological Survey - Science Base
mailing and physical
Building 810, Mail Stop 302, Denver Federal Center
Denver
Colorado
80225
USA
1-888-275-8747
sciencebase@usgs.gov
https://www.sciencebase.gov/catalog/item/5fa5aee1d34ed3698f92dfcc
Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty.
20201215
Bradley S Van Gosen
U.S. Geological Survey
mailing
Mail Stop 973, PO Box 25046
Denver
CO
80225
USA
1-303-236-1566
bvangose@usgs.gov
FGDC Content Standards for Digital Geospatial Metadata
FGDC-STD-001-1998
none
none