Layer, P.W. Benowitz, J.A. Freeman, L.K. 2011 tabular digital data Raw Data File RDF 2011-2 Fairbanks, Alaska - USA State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys 23 pp. http://www.dggs.alaska.gov/pubs/id/22482 40Ar/39Ar data from plutonic, dike, and alteration samples collected during geologic mapping of the eastern part of the Bonnifield mining district geologic map area in parts of Fairbanks A-1 and Fairbanks A-2 and Healy D-1 and Healy D-2 quadrangles yield results indicating the plutons, dikes, and a gold-bearing quartz vein in the Bonnifield Map area range from 85 to 95 m.y. In 2008, the Alaska Division of Geological & Geophysical Surveys (DGGS) conducted a geologic mapping project in parts of the Fairbanks A-1, Fairbanks A-2, Healy D-1, and Healy D-6quadrangles. Our purpose was to map the bedrock geology at a scale of 1:50,000 as part of the Alaska Geophysical/Geological Mineral Inventory (AGGMI) program investigations in the Bonnifield mining district. DGGS published geochemical data resulting from the 2008 work in 2009 (Freeman and others, 2009a). A brief discussion of the results was given in Freeman and others (2009b) and Freeman and others (2010). The purpose of this DGGS Raw Data File is to present the 40Ar/39Ar results and make them available for use to the public that are interested in the area. Attribute information for the three tables (entities) is included in this metadata file under the "Entity_and_Attribution_Information" section. The tables are hierarchical with the SampleLocationDescription table being the parent of of the SummaryAges table which is in turn the parent of StepHeatingData table. The the tables are connected by the SampleNumber and DatedMaterial columns. All tables comprise a single layer as follows: >ArgonGeochronologicData: SampleLocationDescription, SummaryAges, and StepHeatingData 062008 072008 ground condition Complete None planned -147.8028 -147.1864 64.0634 62.9455 ISO 19115 Topic Category geoscientificInformation None Geology 40Ar/39Ar Age Dates Geochronology STATEMAP Project None Alaska, State of Alaska Range Fairbanks Quadrangle Healy Quadrangle Denali Borough Wood River West Fork Little Delta River Dry Creek Kansas Creek Chute Creek Rogers Creek Sheep Creek Glacier Creek Threemile Creek Snow Mountain Gulch Slide Creek Glory Creek Red Mountain Creek Newman Creek Forgotten Creek Slate Creek WTF (Western Tundra Flats) prospect Red Mountain Creek prospect Dry Creek prospect LEA Creek prospect Buzby prospect Smog prospect Glory Creek prospect Kansas Creek prospect Dry Creek placer mine Newman Creek placer mine None Cretaceous Late Cretaceous This report and/or dataset is available directly from the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (see contact information below). Any hard copies or published datasets utilizing these datasets shall clearly indicate their source. If the user has modified the data in any way, the user is obligated to describe the types of modifications the user has made. User specifically agrees not to misrepresent these datasets, nor to imply that changes made by the user were approved by the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys. State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys GIS Data Manager/Cartographer mailing and physical

3354 College Road

Fairbanks AK 99709-3707 (907) 451-5029 (907) 451-5020 (907) 451-5050 dggspubs@alaska.gov You may view our web site at http://www.dggs.alaska.gov/ for the latest information on available data.Please e-mail your questions and data requests when possible since our web site and e-mail address will remain current even if our phone number and mailing address change. This project is part of the Alaska Airborne Geophysical/Geological Mineral Inventory Program funded by the Alaska State Legislature and managed by the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys. Partial funding for the geologic mapping and 39Ar/40Ar geochronology was also provided through the State of Alaska General Fund and the U.S. Geological Survey STATEMAP Program under award number 08HQAG0051. Samples were collected as part of the geologic mapping program during 2008 by J.E. Andrew, M.B. Werdon, D.J. Szumigala, and L.K Freeman of DGGS and by R.J. Newberry of the Department of Geology & Geophysics, University of Alaska Fairbanks Microsoft Windows XP SP2, Microsoft Excel 2003 Coordinates of sample locations were determined by the geologists in the field using Garmin 12XL GPS receivers with no differential correction. The coordinates were recorded in field notes along with hand sample descriptions and other locality information. The coordinates were up-loaded into an MS Access database and were checked against recorded coordinates in geologists field notes. DGGS submitted eight rock samples to the UAF Geochronology Laboratory for 40Ar/39Ar dating. Separates for 40Ar/39Ar dating were prepared to >99.5% purity (visual inspection) using standard heavy liquid and magnetic separation techniques followed by hand-picking under a binocular microscope.Thin section examination of the samples prior to crushing indicated that the chosen minerals were free from alteration and sufficiently coarse-grained for mechanical separation.For all minerals, grains in the size range of 250 - 500 microns were used.For each sample, ~50-80 mg of biotite or 250-350 mg of hornblende or whole rock (phenocryst-free groundmass) was packaged in an aluminum foil tube and irradiated in position 5C at the McMaster University nuclear reactor, in Hamilton, Ontario.Approximately 20 samples were irradiated at a time.Six packages containing ~20 mg of the standard mineral mmhb-1 (Samson and Alexander, 1987) with an age of 513.9 Ma (Lanphere and others, 1990) were also irradiated with the samples to determine the irradiation parameter (J) and the flux gradient in the reactor.Samples and standards were analyzed 45 to 90 days after irradiation. The irradiated samples were step-heated on-line in a Modifications Ltd. low-blank furnace.Temperature control was better than 5 degrees and a maximum temperature in excess of 1600o C was achievable to ensure complete sample fusion.The extracted argon was purified in a two-stage process using a liquid nitrogen cold finger and two SAES Zr-Al getters.Prior to measurement of the Ar, the gas was collected on an activated charcoal finger.The purified Ar gas was measured using a Nuclide 6-60-SGA 15 cm mass spectrometer.The sensitivity of the spectrometer is 6.5 x 10-15 mol/mV and system noise is generally around 0.02 mV.System blanks are generally better than 1 X 10-14 mol for 40Ar.Argon isotopic measurements for both samples and standards were corrected for the system blanks, for decay of37Ar and 39Ar, and for reactor-induced isotopic interferences.Ages were calculated using the equations and corrections from McDougall and Harrison (1999) and the constants from Steiger and Jaeger (1977) and are shown in Table 2 (age summary) and Table 3 (analytical data).All errors on analyses are reported at the 1-sigma level. For each mass spectrometer analysis, five Ar isotope abundances are measured.36Ar is used to determine the amount of atmospheric or initial Ar in the sample, 37Ar provides an estimation of the Ca content in the mineral, 38Ar provides an estimation of the Cl content, 39Ar reflects the K content and 40Ar is a mixture of initial and radiogenic Ar.The age of the sample is proportional to the ratio of the amount of radiogenic 40Ar to the amount of 39Ar produced by neutron bombardment from 40K. No topologic relationships are present in the data. Sample numbers in the each of the three tables were recorded by geologists in the field, recorded on sample bags and on field note sheets. The sample numbers were transcribed into an Access database by a field assistant. Table 1 was generated from the database and was cross checked against the sample numbers recorded on the bags for consistency. Sample numbers in tables 2 and 3 were generated by the UAF geochronology lab from the a list provided by DGGS and cross checked with sample numbers on the bags. We are certain that the sample numbers in the table are logically correct. This dataset includes all of the samples submitted for 40Ar/39Ar age date analyses from the Healy and Fairbanks quadrangle that were collected by DGGS during the summer of 2008. All field locations were determined by the geologists in the field using Garmin 12XL GPS receivers with no differential correction. 10 All field locations were determined by the geologists in the field using Garmin 12XL GPS receivers. Estimated position errors as calculated by the Garmin 12XL receivers were recorded in the field and range from 3 to 6 meters for the samples used in this data. Freeman, L.K. Werdon, M.B. Szumigala, D.A. Andrew, J.A. Newberry, R.J. Athey, J.A. 2009 tabular data Alaska Division of Geological & Geophysical Surveys Raw Data File RDF 2009-1 69 p. paper and digital 2009 publication date Freeman and others, 2009a Provides chemical data for classification and description of samples Freeman, L.K. Newberry, R.J. Andrew, J.A. Werdon, M.B. Szumigala, D.A. Athey, J.A. Burns, L.E. 2009 poster presentation Geological Society of America Abstracts with Programs v. 41, no. 7 (abstract), P. 282 paper 2009 publication date Freeman and others, 2009b Describes field work and initial geologic findings, reports preliminary ages Lanphere, M.A. Dalrymple, G.B. 2000 document U.S. Geological Survey Professional Paper 1621 10 p. paper 2000 publication date Lanphere and Dalrymple, 2000 Describes inter-calibration standards Samson, S.D. Alexander, E.C. 1987 journal article Chemical Geology v. 66 p. 27-34 paper 1987 publication date Samson and Alexander, 1987 Inter laboratory calibration data for age determination York, D. Hall, C.M. Yanase, Y. Kenyon, W.J. 1981 journal article Geophysical Research Letter v. 8 p. 1136-1138 paper 1981 publication date York, and others, 1981 Description of laser heating mass-spectrographic analysis method Layer, P.W. Hall, C.M. York, D. 1987 journal article Geophysical Research Letter v. 14 p. 757-760 paper 1987 publication date Layer and others, 1981 Description of laser step-heating mass-spectrographic analysis method Layer, P.W. 2000 journal article Meteoritics and Planetary Science v. 35 p. 591-599 paper 2000 publication date Layer, 2000 Description of laser step-heating mass-spectrographic analysis method McDougall, I Harrison, T.M. 1999 2 book chapter Oxford Oxford University Press 269 pp. paper 1999 publication date McDougall and others, 1999 Source reference for equations and corrections used in age calculation. Steiger, R.H. Jager, E. 1977 document Earth and Planetary Science Letters v.36 p. 359-363 paper 1977 publication date Steiger and Jager, 1977 discussion of use of decay constants in age determination Fieldwork - The eastern Bonnifield map area, including parts of the Fairbanks A-1, A-2, Healy D-1, and Healy D-2 quadrangles was mapped at 1:50,000 scale. As part of the mapping geologic, samples of igneous rocks and mineralized rocks with sericite were collected as potential samples for geochronology. Sample locations were determined using Garmin 12 XL GPS receivers. Field descriptions were recorded onto field note forms which were later transcribed into a MS Access database by a geological field assistant. Freeman and others, 2009b 200807 Sample selection - A list of samples that were collected for radiometric ages was generated from th MS Access database and checked against available samples. Petrographic thin sections for the prospective samples were examined to eliminate samples that were altered. Sample locations were plotted in GIS along with the preliminary geologic map to determine which samples would provide the most geologically significant age information. Freeman and others, 2009b 200812 Sample description - Sample descriptions were generated from field descriptions, petrographic descriptions, and major oxide geochemistry. The sample descriptions were also used in Freeman, and others, 2009 Freeman and others, 2009a 200901 Sample preparation - Mineral separates for 40Ar/39Ar dating were prepared to greater than 99.5 percent purity (determined by visual inspection) where they were crushed, sieved, washed, and hand-picked for mineral phases or small, phenocryst-free whole-rock chips. The monitor mineral MMhb-1 (Samson and Alexander, 1987) with an age of 513.9 Ma (Lanphere and Dalrymple, 2000) was used to monitor neutron flux (and calculate the irradiation parameter, J). The samples and standards were wrapped in aluminum foil and loaded into aluminum cans 2.5 cm in diameter and 6 cm in height. The samples were irradiated in position 5c of the uranium-enriched research reactor of McMaster University in Hamilton, Ontario, Canada, for 20 megawatt-hours. Samson and Alexander, 1987 Lanphere and Dalrymple, 2000 200903 Sample analysis - Upon their return from the reactor, the samples and monitors were loaded into 2-mm-diameter holes in a copper tray that was then loaded into an ultra-high-vacuum extraction line. The monitors were fused and samples heated using a 6-watt argon-ion laser following the technique described in York and others(1981), Layer and others (1987), and Layer (2000). Argon purification was achieved using a liquid nitrogen cold trap and an SAES Zr-Al getter at 400C. The samples were analyzed in a VG-3600 mass spectrometer at the Geophysical Institute, University of Alaska Fairbanks. The argon isotopes measured were corrected for system blank and mass discrimination, as well as calcium, potassium, and chlorine interference reactions following procedures outlined in McDougall and Harrison (1999). System blanks generally were 2x10e-16 mol 40Ar and 2x10e-18mol 36Ar, which are 10 to 50 times smaller than fraction volumes. Mass discrimination was monitored by running both calibrated air shots and a zero-age glass sample. These measurements were made on a weekly to monthly basis to check for changes in mass discrimination. A summary of all the 40Ar/39Ar results is given in table 2, with all ages quoted to the +-1 sigma level and calculated using the constants of Steiger and Jaeger (1977). The integrated age is the age given by the total gas measured and is equivalent to a potassium-argon (K-Ar) age. The spectrum provides a plateau age if three or more consecutive gas fractions represent at least 50 percent of the total gas release and are within two standard deviations of each other (Mean Square Weighted Deviation less than ~2.5). All samples were run three times to verify sample consistency. York, and others, 1981 Layer, and others, 1987 Layer, 2000 McDougall and Harrison, 1999 Steiger and Jaeger, 1977 200905 Point Universal Transverse Mercator 6 0.9996 -147 0 500000 0 coordinate pair 1 1 meters ArgonGeochronologicData North American Datum of 1927 Clarke 1866 6378137 298.25722210088 ArgonGeochronologicData SampleLocationDescription.csv Location and description of rock samples collected for trace-element geochemical analyses in the eastern Bonnifield mining district, Fairbanks and Circle quadrangles, Alaska Alaska Division of Geological & Geophysical Surveys SampleNumber Unique sample identifier Alaska Division of Geological & Geophysical Surveys Generic example of unique sample identifier: 20YYAAA9999X: YY=last two digits of year, AAA=geologist's initials (one to three characters), 9999=unique station number, X=unique alpha character designating a sample was taken at the field station. Geologists' initials represent the following: 'JOE' = Joe Andrew; 'LF' = Larry Freeman; 'MBW' = Melanie Werdon; 'RN' = Rainer Newberry; 'Z' = David Szumigala. Latitude Latitude in decimal degrees, NAD 27 Alaska Division of Geological & Geophysical Surveys 63.8411 64.066 decimal degrees Longitude Longitude in decimal degrees, NAD 27 Alaska Division of Geological & Geophysical Surveys -147.8358 -147.3248 decimal degrees UTME Easting Alaska Division of Geological & Geophysical Surveys 459098 484148 meters UTMN Northing Alaska Division of Geological & Geophysical Surveys 7079208 7104209 meters Zone UTM Zone Alaska Division of Geological & Geophysical Surveys "6" indicates 06W NAD27 Alaska Projection Description1 Brief rock description part 1 0f 3 (truncated to 255 characters) Alaska Division of Geological & Geophysical Surveys Brief rock description Description2 Brief rock description part 2 of 3 (for descriptions longer than 255 characters) Alaska Division of Geological & Geophysical Surveys Brief rock description Description3 Brief rock description part 2 of 3 (for descriptions longer than 510 characters) Alaska Division of Geological & Geophysical Surveys Brief rock description ArgonGeochronologicData SummaryAges.csv Summary of 40Ar/39Ar radiometric ages of samples in this report. Preferred interpreted ages are underlined in the Adobe Acrobat portable document version of the tables. Alaska Division of Geological & Geophysical Surveys SampleNumber Unique sample identifier, corresponds to "SampleNumber" attribute in "SampleLocationDescription.csv Alaska Division of Geological & Geophysical Surveys Generic example of unique sample identifier: 20YYAAA9999X; Where: YY=last two digits of year, AAA=geologist's initials (one to three characters), 9999=unique station number, X=unique alpha character designating a sample was taken at the field station. Geologists' initials represent the following: 'JOE' = Joe Andrew; 'LF' = Larry Freeman; 'MBW' = Melanie Werdon; 'RN' = Rainer Newberry; 'Z' = David Szumigala. DatedMaterial Material used for age date Alaska Division of Geological & Geophysical Surveys Identifies material that was used to for the age analysis includes either mineral name for mineral seperates or "Whole Rock" for samples of fine-grained or aphanitic groundmass. Some samples were run as duplicates. IntegratedAgeMa Integrated age and age error in million years (Ma). Alaska Division of Geological & Geophysical Surveys 84.3 +- 0.5 111.1 +- 1.3 Ma PlateauAgeMa Plateau age and age error in million years (Ma) for each sample. Preferred interpreted ages are underlined in the Adobe Acrobat portable document version of the tables. Null values indicate that the age could not be determined. Alaska Division of Geological & Geophysical Surveys 64.2 +- 1.0 102.5 +- 1.5 Ma PlateauInformation Describes the number of fractions, percent 39Ar released, and Mean Standard Weighted Deviation (MSWD) used for the plateau age. Null values indicate that the age could not be determined. Alaska Division of Geological & Geophysical Surveys number of fractions, % 39Ar released, MSWD. IsochronOrOtherInformation Lists the isochron age and information of the isochron age if appropriate. Comments regarding some of the other age analyses are also listed in this column. Alaska Division of Geological & Geophysical Surveys If an isochron age is listed the column contains the age and age error in Ma, the initial ratio and error of 40Ar to 36 Ar (40Ar/36Ari), number (N) of fractions, and the Mean Standard Weighted Deviation (MSWD). Other values include "Loss Spectrum", "Reset, and "Reset/Loss". ArgonGeochronologicData StepHeatingData.csv The Step heating data is the root 40Ar/39Ar analytical data associated with each recorded Power output level for each run of dated material from a sample in this report. Alaska Division of Geological & Geophysical Surveys SampleNumber Sample number contains an identifier that along with the "DatedMaterial" column relates the Step Heating data to the "SummaryAges" entity. The "SampleNumber" attribute corresponds to the "SampleNumber' attribute inboth the "SampleLocationDescription" and "SummaryAges" entities. Alaska Division of Geological & Geophysical Surveys Generic example of unique sample identifier: 20YYAAA9999X; Where: YY=last two digits of year, AAA=geologist's initials (one to three characters), 9999=unique station number, X=unique alpha character designating a sample was taken at the field station. Geologists' initials represent the following: 'JOE' = Joe Andrew; 'LF' = Larry Freeman; 'MBW' = Melanie Werdon; 'RN' = Rainer Newberry; 'Z' = David Szumigala. DatedMaterial Dated Material contains a string describing the material used to for the analysis along with the "SampleNumber" attribute relates the "StepHeatingData" entity to the "SummaryAges" entity. The information in this attribute and corresponds to the "Dated Material" attributes in the "SummaryAges" entity respectively. Alaska Division of Geological & Geophysical Surveys Identifies material that was used to for the age analysis includes either mineral name for mineral seperates or "Whole Rock" for samples of fine-grained or aphanitic groundmass. Some samples were run as duplicates. Laser_mW Laser output level in megawatts, or "integrated" of each heating step University of Alaska Department of Geosciences Geochronology Laboratory 300 9000 Megawatts Integrated Indicates row of data from entire step heating run Alaska Division of Geological & Geophysical Surveys and ALS Chemex. Cum39Ar Cumulative ratio of 39Argon released at this step. Null indicates that a cumulative value is not appropriate. Alaska Division of Geological & Geophysical Surveys 0.0022 1.0001 Ratio40Ar39ArMeasured Measured 40Ar/39Ar ratio for each heating step, corrected for blank and 39Ar decay Alaska Division of Geological & Geophysical Surveys -87.3886 887.4823 Ratio40Ar39ArMeasuredError The one sigma error for each 40Ar/39Ar measurement. Alaska Division of Geological & Geophysical Surveys 0.0332 122.5255 Ratio37Ar39ArMeasured The ratio of measured 37Ar to measured 39Ar for each heating interval for each sample corrected for blank and 37Ar and 39Ar decay Alaska Division of Geological & Geophysical Surveys -0.4268 0.6338 Ratio37Ar39ArMeasuredError The one sigma error for each 37Ar/39Ar measurement. Alaska Division of Geological & Geophysical Surveys 0.0001 2.7043 Ratio36Ar39ArMeasured Ratio of measured 36Ar to measured 39Ar for each step interval for each sample corrected for blank and 39Ar decay Alaska Division of Geological & Geophysical Surveys -0.0458 0.6338 Ratio36Ar39ArMeasuredError The one sigma error for each 36Ar/39Ar measurement. Alaska Division of Geological & Geophysical Surveys 0.0000 0.7423 PercentAtm40Ar Percent of 40Ar which is atmospheric in composition at each step level Alaska Division of Geological & Geophysical Surveys -107.7808 1044.4022 RatioCaK ratio of Calcium to Potassium as determined from 37Ar/39Ar Alaska Division of Geological & Geophysical Surveys -0.0047 20.4314 RatioCaKError The one sigma error for each Ca/K determination. Alaska Division of Geological & Geophysical Surveys 0.0001 4.9721 RatioClK ratio of Chlorine to Potassium as determined from 38Ar/39Ar Alaska Division of Geological & Geophysical Surveys -0.0002 0.1204 RatioClKError The one sigma error for each Cl/K determination. Alaska Division of Geological & Geophysical Surveys 0.0000 0.0964 Ratio40ArRad39ArK ratio of radiogenic 40Ar to 39Ar derived from potassium Alaska Division of Geological & Geophysical Surveys 5.592 783.8764 Ratio40ArRad/39ArKError One sigma error for each 40ArRad/39ArK value Alaska Division of Geological & Geophysical Surveys 0.0403 147.7079 AgeMa calculated age for each temperature step for each sample Alaska Division of Geological & Geophysical Surveys 35.9800 2418.7300 Millions of years AgeErrorMa one sigma error of the age determination of each heating step Alaska Division of Geological & Geophysical Surveys 0.2500 841.5300 Millions of years WeightedAverageOfJFromStandards one sigma error of the age determination of each heating step Alaska Division of Geological & Geophysical Surveys J value, calculated from the weighted average of standards placed in various positions in the nuclear reactor State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys mailing and physical

3354 College Road

Fairbanks AK 99709-3707 USA 907-451-5020 907-451-5050 dggspubs@alaska.gov 8 am to 4:30 pm, Monday through Friday, except State holidays Please view our web site (http://www.dggs.alaska.gov) for the latest information on available data. Please contact us using the e-mail address provided above when possible. The State of Alaska makes no express or implied warranties (including warranties of merchantability and fitness) with respect to the character, function, or capabilities of the electronic services or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products, any failure thereof, or otherwise, and in no event will the State of Alaska's liability to the requester or anyone else exceed the fee paid for the electronic service or product. Current publication is available on paper. To purchase this or other printed reports and maps, contact DGGS by phone (907-451-5020), e-mail (dggspubs@alaska.gov), or fax (907-451-5050). Payment accepted: Cash, check, money order, VISA, or MasterCard. http://www.dggs.alaska.gov/pubs/id/22482 PDF 1.6 No compression applied http://www.dggs.alaska.gov/pubs/id/22482 Free download CSV No compression applied http://www.dggs.alaska.gov/pubs/id/22482 Free download DGGS publications are available as free online downloads or you may purchase paper hard-copies or digital files on CD/DVD or other digital storage media over the counter by mail, phone, fax, or email from the DGGS Fairbanks office.Turn around time is 1-2 weeks unless special arrangements are made and an express fee is paid. Shipping charge will be the actual cost of postage and will be added to the total amount due. Contact us for a exact shipping ammount. 20110622 Metadata manager mailing and physical

State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys

Fairbanks AK 99709-3707 USA 907-451-5020 FGDC Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998 If the user has modified this metadata file in any way, the user is obligated to describe the types of modifications the user has made. User specifically agrees not to misrepresent this metadata file, nor to imply that changes made by the user were approved by the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys. http://www.dggs.alaska.gov/metadata/dggs.ext dggs metadata extensions