Mineral Resources On-Line Spatial Data
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1) Coordinates: When samples were brought in for analysis, the submitter was required to include information about the sample for the database; descriptions, geocoding, and latitude-longitude coordinates. In the days before map digitizing boards and GPS units were common, the deter-mination of coordinates from field sheets was a time consuming and error prone process. In order to facilitate the analysis of samples, a deci-sion was made to allow submitters to enter the coordinates for the lower left (SW) corner of the submitter's working field map on which the samples could be plotted, which was most commonly a 7.5' or 15' quad- rangle map. In theory, the precise coordinates for these samples would be determined and added to the database at a later date. In practice, most of these precise coordinates were used in the USGS Open-File data releases but were never entered back into the PLUTO database. There-fore, the precision of coordinates in the PLUTO database varies from "good to the nearest second of latitude or longitude" to "good to the nearest 15 minutes of latitude or longitude".
2) Earth Ellipsoid or Datum: Since most of the coordinate data in the PLUTO database were determined from published USGS maps and not from recent GPS systems, the coordinates are based on the 1927 North American datum (also known as the Clarke 1866 ellipsoid). Most modern GPS sys-tems use the 1983 North American datum (NAD 83) or the World Geodetic System (WGS 84). If the PLUTO data are plotted using the wrong ellip-soid or datum, the location may be offset by a distance up to a couple hundred feet.
3) Geocoding: The submission of geocoding with samples was mandatory for some fields and optional for others. Therefore, the completeness of geocoding can vary. In addition, most geocodes were not checked for completeness, accuracy, or validity during data entry into the database. Therefore the PLUTO database contains some incorrect and invalid codes.
4) One geocode, the Material Code <MAT> was required. The Material Code designates the type of sample media analyzed. Unfortunately, there was no specific material code for "Heavy- Mineral-Concentrate" samples prior to 1991. Most, but not all, concentrate samples submitted since 1991 have a Material Code of K. Before 1991, most concentrate samples were coded as A (rock), D (unconsolidated sediment), or Z (other) based upon the parent material. The most common problem is in distinguishing pre-1991 stream sediments from heavy-mineral concentrates. The user should check the <B12> geocoding field for indication that the sample was "processed". Many times concentrate samples can also be determined from the contents of the <DESC> description field. Additionally, the field number <FLDNO> for a concentrate sample will commonly have a suffix of C, C1, C2, C3, H, HM, or HN.
5) The PLUTO database contains a considerable amount of data for coal samples, although there is no specific material code for coal. The material code for all coal samples in the database is I (Organic fuel or related substance). The <DESC> description field is the most useful secondary field for identifying coal samples in the database. The analytical data on coal samples includes data on both whole coal and coal ash. Coal ash data is indexed in the database with "/A" following the element symbol (for example SiO2/A is silicon dioxide in ash). The ash data can be converted to a whole coal basis using the tabulated ash value (percent of sample remaining after combustion). We have observed that a large amount of the data for coal ash in the database (particularly spectroscopic data) has been entered as if the data were on the whole coal (i.e. without the "/A" designation on the index).
6) Qualifiers: Many analytical data values in the PLUTO database are accompanied by a qualifier - N, L, G, H, B which for compatibility with the GSBUILD/GSSEARCH software has been converted to numeric representa-tions: N = 1; L = 2; G = 3; H = 4; B = 5. The qualifiers are defined as follows:
N = Concentration was looked for but not detected at tabulated value L or < = Concentration is less than the tabulated value G or > = Concentration is greater than the tabulated value H = The concentration could not be precisely determined because of interferences B = Concentration was not determinedThe distinction between a value qualified by an N or an L is small and was not applied consistently between different types- of-analysis. For some semi-quantitative spectrographic methods, an N was used when an element concentration could not be detected and an L was used when the element could be detected but the concentration was below determination limits that could confidently be reported. In other words, a value qualified with an L was slightly more significant than one qualified with an N. However for other analytical methods, a concentration below the determination limits of the method may be qualified with either an N or an L depending upon the method, the analyst, or the laboratory. Therefore without specific knowledge of these factors, the safest way to treat values qualified with an N or an L is as "less than the tabulated value".
7) The data in the PLUTO CD-ROM database was entered manually by the analyst, or electronically via automatic data transfer from laboratory instruments. We have occasionally observed data in the database where we suspect there have been errors in data entry, or data tranmission (i.e. major element analyses that sum to greater than 1 gram/gram, or trace element analyses with unlikely exponents). It has not been possible to do a complete quality control check on the entire database. Therefore we encourage all users of the database to check the data with a critical eye. Are the analytical data geochemically consistent with the sample description as provided by the "geocoding"?
Each sample must have a valid lab number (one character + 7 digits) Each sample must have a valid state/location code. Each sample must have a valid material code. Each sample must have a valid latitude and longitude. Each sample must be from the U.S. (including Alaska and Hawaii). Each sample must contain valid analytical data.All data that have Latitude and Longitude values that fall within the boundaries of Indian reservations have also been deleted from the CD-ROM database, except for the Goshute and Wind River reservations. The deleted data is considered proprietary information by the corresponding reservations, and has not been approved for release.
In the original PLUTO database the element fields are identified by numerical identification codes ("NIDS") which are defined by chemical species, units of concentration, and, in come cases, by analytical technique. "NIDS" in the PLUTO database are not preserved in the CD-ROM data base. All "NIDS" are converted either to the corresponding oxide (for major/minor elements) or to the element symbol (for minor or trace elements). (Data for multiple oxidation states are retained: e.g. Cr, CrO3, Cr2O3, Mn, MnO, MnO2, Mn203, FeO, Fe2O3, FeTO3.)
The latitude and longitude are checked to see if they fall within the state and county specified. If the latitude and longitude fall outside the listed state and county, the distance in km of the tabulated lat. and long. from the specified county is reported in a separate field.
Duplicate analytical results are deleted if the Type-of-analysis (TOA) codes are the same or if one or the other TOA code is missing. All missing data values have been deleted.
Units (as defined by the "NIDS" in the PLUTO database) are not preserved in the CD-ROM data base. All data are reported in units of grams of analyte per gram of sample.
Many samples in the PLUTO data set are missing the county code. If the county code is missing (or invalid), it is defined based on the latitude and longitude values, providing the state code is consistent with the latitude and longitude values. If the county code is present it must be valid for the specified state.
2) Earth Ellipsoid or Datum: Since most of the coordinate data in the PLUTO database were determined from published USGS maps and not from recent GPS systems, the coordinates are based on the 1927 North American datum (also known as the Clarke 1866 ellipsoid). Most modern GPS sys-tems use the 1983 North American datum (NAD 83) or the World Geodetic System (WGS 84). If the PLUTO data are plotted using the wrong ellip-soid or datum, the location may be offset by a distance up to a couple hundred feet.
(a) All records were fieldname MAT = A (Igneous rock)
(b) Required that record had SIO2 present (silicon dioxide)
- Using file conversion utility (ASCCNURT), 12 WK1 files were created based on analytical method
Note: Each record had to have a method code of WX (wavelength dispersive XRF), AA (atomic absorption), QS (quantitative spectroscopy), or ZZ (unknown, mostly old wet-chemical data).
(2) Imported WK files into Excel and created a subset based on the following:
(a) Deleted trace elements
(b) Deleted any No Data records
(c) Deleted records with missing major elements
(d) Deleted records with major elements too high for reliable determination
(e) Expanded Geocoding Codes based on the manual:
Instructions for submitting samples to Branch of Geochemistry: Sample submittal manual (4th edition 1993), published as USGS Open-File Report 93-533
(f) removed several unused fields
(g) Replaced any number that had a "<" qualifier (below detection limit) with a negative number having the same absolute value.
(h) Deleted records containing data with other qualifiers.
Created DBF file of sample locations
(i) Imported DBF file into ArcView 3.1 and created shapefile (pluto-ig.shp)
Labno Laboratory identification number of sample field Field name assigned by geologist full_name Previous two names concatenated together. Jobn Analytical job identification number State State where sample was collected county County where sample was collected latitude Latitude where sample was collected longitude Longitude where sample was collected formation Geological formation hosting sample descriptio Geologist's description of the sample Name Name of geologist who submitted sample for analysis Sub_date Date of submission for analysis character Indicates how typical sample is of an area and how it was collected. source Source of sample (outcrop, mine, float, etc.) Age Geological age of sample coded by the submitter. rock_from Generic form of the rock (lava flow, xenolith, etc.) texture_st Texture and structure of rock. qtz_feldsp Quartz-feldspar occurrences and relationships. rock_name Igneous rock type (basalt, granite, etc.) econom_ge Mineralization noted by geologist in sample. method Analytical method used for major elements. sio2 Analytical result in weight percent. al2o3 Analytical result in weight percent. Mgo Analytical result in weight percent. Cao Analytical result in weight percent. Na2o Analytical result in weight percent. K2o Analytical result in weight percent. Tio2 Analytical result in weight percent. p2o2 Analytical result in weight percent. Mno Analytical result in weight percent. Feto3 Analytical result (Total iron as iron 3+) in weight percent. sum Sum of above. Fe2o3 Analytical result in weight percent. Feo Analytical result in weight percent. H2o_plus Analytical result in weight percent. H2o_minus Analytical result in weight percent. Co2 Analytical result in weight percent.
U.S. Department of the Interior |
U.S. Geological Survey
URL: http://tin.er.usgs.gov/metadata/plutoig2.html
Page Contact Information: Peter Schweitzer
Page Last Modified: Thursday, 18-Oct-2007 13:17:58 EDT
