DNR Open-File Project 378: Koochiching County Archean Greenstone Drill Core Assays

1. About this project


Map of the 13 Drill Core Locations (click for detail)

This new work consists of laboratory analysis of 166 drill core samples (including standards and duplicates) by ALS Chemex. The samples were selected from 9 drill cores that had been drilled during the 1980’s, primarily by exploration companies searching for gold and base metals. Drill core and related exploration data are currently available at the Minnesota Department of Natural Resources Drill Core Library in Hibbing, Minnesota.

Sampling was guided by re-logging of the core and also by the use of a  hand-held X-Ray Fluorescence (XRF) analyzer instrument. Files contain these new sample assays including standards and duplicates, new core logs, XRF data and core locations.

Project Leader: Barry Frey
1525 Third Avenue East 
Hibbing, Minnesota 55746
tel. (218) 231-8450
barry.frey@state.mn.us

 

2. Report and Data Released October 1, 2012

October 1, 2012 - OPEN-FILE REPORT: INTERNATIONAL FALLS DRILL CORE DESCRIPTIONS AND CHEMISTRY, KOOCHICHING COUNTY, MINNESOTA, PROJECT 378. Project 378

This data release consists of the final report for Project 378 and related digital files. The Project 378 drill cores are located within an accessible Archean greenstone terrane near International Falls, Minnesota. The Quetico fault system is prominent in this area. Besides low-grade gold mineralization, the chemical data and logging identified thin sphalerite-bearing intervals and abundant tourmaline (see Figure 1 in P378 Report, for drill core locations).

Data includes laboratory analyses of 231 analyses including 217 drill core samples, duplicates, and standards, by ALS Chemex. The samples were selected from 13 drill cores that had been drilled during the 1980’s, primarily by exploration companies searching for gold and base metals. Drill core and related exploration data are currently available at the Minnesota Department of Natural Resources Drill Core Library in Hibbing, Minnesota.

Sampling was guided by re-logging of the core and also by the use of a hand-held X-Ray Fluorescence (XRF) analyzer instrument. The hand-held XRF targets a circular area of 0.76 cm2 , providing semi-quantitative chemical data at a scale between chemistry lab analyses (over feet) and microprobe (over microns) chemistry. The scale is ideal for smaller features, and is amenable to creating comparative traverses across veins and lithologic contacts; and comparative chemistry, with and without, small features such as sulfide blebs.

Zinc is present in small amounts in some drill cores in this area. It has been reported elsewhere that zinc may interfere with the XRF gold analysis and cause the gold content to be over-estimated. Therefore, we emphasize that these XRF analyses are semi-quantitative and are used as a tool to refine the logging and sample selection for traditional chemical analyses and fire assays.

This data release supercedes previous data releases for Project 378, including September 2010 and March 2011 data releases for this project.

 

3. Data released  March 23, 2011

This data release supercedes the September 2010 data release for this project. Today’s set of chemical analyses is combined with the data release of September, 2010 to provide a total of 227 samples from 13 drill holes for this Archean greenstone terrane near International Falls (see map for drill core locations). The author also re-logged the cores and now provides 12 new drill core logs. The drill cores are located within an accessible Archean greenstone terrane near International Falls, Minnesota. The Quetico fault system is prominent in this area. Besides low-grade gold mineralization, the chemical data and logging identified thin sphalerite-bearing intervals and abundant tourmaline. This area is offered in the State’s mineral lease sale on April 28, 2011.

A zip file is released that includes all of the following files (project378_data032211.zip):

  • Word file with data release organization and limitations (Read_OF03-11_P378.doc)
  • Excel file sample drill hole location/DNR standard information (P378chem_samp_info3_11.xls)
  • CSV file of new received chemistry data (RE11023552.csv)
  • CSV file of new received chemistry/sample prep data (RE11023552_wSamplePrep.xls)
  • CSV file of new received chemistry/internal standards data (RE11023552-1_Standards.xls)
  • CSV file of new received chemistry/duplicates data (RE11023552-2_Duplicates.xls)
  • Excel file with new ALS Chemex laboratory results (RE11023552.xls)
  • PDF file of new received chemistry results (COA_RE11023552_29190-14761428.pdf)
  • Excel file all sample descriptive and location information, received chemistry results (P378_Chem_Shape_AB6.xls)
  • Excel file with semi-quantitative XRF results and descriptions (13 DDH’s) (P378_XRF_IfallsD.xls)
  • Excel file with general lithologic logs for 12 DDH’s (P378_General_Log_partial.xls)
  • ESRI shapefile for the locations of the 13 drill cores that were analyzed in Project 378 (p378_exploration_drill_holes.shp)
  • General metadata for p378_exploration_drill_holes.shp.  This metadata provided here is referencing the entire drill core database (p378_exploration_drill_holes_metadata.pdf)
  • CSV file of earlier chemistry data (RE10075765.csv)
  • Excel file with ALS Chemex laboratory results (P378_OpenFile_09-10_Chemistry.xls)
  • PDF file of earlier chemistry results (COA_RE10075765_29190-12155671.pdf)
  • Excel file with DNR submitted standards and accepted values (P378_OpenFile_09-10_Chem_Standards.xlsx)
  • PDF file of ALS Chemex quality control - earlier data (P378_QCDOC_RE10075765.pdf)
  • CSV file of earlier chemistry quality control data (RE10075765QC.csv)
  • Excel file sample descriptive and location information, earlier chemistry results, and some basic statistics (P378_RE10075765fin.xlsx)

The following map is released as a pdf:

The following presentation is released as a pdf:

Please note: Best results in viewing these reports will be obtained by saving the files to a location of your choice and opening with Adobe Reader or Acrobat. Some report information may not display as a result of opening with Acrobat directly from a web browser.