Petrographic observations of rocks collected in the Bonnifield mining district, Fairbanks A-1, Fairbanks A-2, Healy D-1, and Healy D-2 quadrangles, Alaska

Frequently anticipated questions:

• What does this data set describe?
  1. How should this data set be cited?
  2. What geographic area does the data set cover?
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
  7. How does the data set describe geographic features?
• Who produced the data set?
  1. Who are the originators of the data set?
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
• Why was the data set created?
• How was the data set created?
  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
  3. What similar or related data should the user be aware of?
• How reliable are the data; what problems remain in the data set?
  1. How well have the observations been checked?
  2. How accurate are the geographic locations?
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
  5. How consistent are the relationships among the data, including topology?
• How can someone get a copy of the data set?
  1. Are there legal restrictions on access or use of the data?
  2. Who distributes the data?
  3. What's the catalog number I need to order this data set?
  4. What legal disclaimers am I supposed to read?
  5. How can I download or order the data?
• Who wrote the metadata?

What does this data set describe?

1. How should this data set be cited?

   Montayne, Simone, Wypych, Alicja, Freeman, L.K., and Griesel, G.A., 2019, Petrographic observations of rocks collected in the Bonnifield mining district, Fairbanks A-1, Fairbanks A-2, Healy D-1, and Healy D-2 quadrangles, Alaska: Raw Data File RDF 2019-1, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

   Online Links:

   • <http://doi.org/10.14509/30171>

   Other_Citation_Details: 4 p.

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -147.829220

   East_Bounding_Coordinate: -147.165490

   North_Bounding_Coordinate: 64.067800

   South_Bounding_Coordinate: 63.840900

3. What does it look like?

4. Does the data set describe conditions during a particular time period?

   Beginning_Date: 2008

   Ending_Date: 2018

   Currentness_Reference: ground condition

5. What is the general form of this data set?

   Geospatial_Data_Presentation_Form: report and digital data

6. How does the data set represent geographic features?
   1. How are geographic features stored in the data set?

      This is a point data set.

   2. What coordinate system is used to represent geographic features?

      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.00001. Longitudes are given to the nearest 0.00001. Latitude and longitude values are specified in decimal degrees.

      The horizontal datum used is North American Datum of 1927.
      The ellipsoid used is Clarke 1866.
      The semi-major axis of the ellipsoid used is 6378206.40000000037.
      The flattening of the ellipsoid used is 1/294.978698199999997.
      

7. How does the data set describe geographic features?

   bonnifield-tx-rock-descriptions.csv, bonnifield-tx-rock-descriptions-metadata.csv

   petrographic thin section lithology observations (Source: Alaska Division of Geological & Geophysical Surveys (DGGS))

   thin_section_id

   The label printed on the thin section slide. Primary key used to uniquely identify each thin section record (Source: this report)

   string

   dggs_sample_number

   The sample number assigned in the field to identify the sample, modified to DGGS standard format. Generic example of a sample identifier: YYAAA999X: YY=last two digits of the year the sample was collected, AAA=geologist's initials (one to three characters), 999=unique station number, X= optional alpha character which indicates that multiple samples were collected at a given location or that multiple observations were recorded in the project database. This number is used to identify corresponding records in the DGGS geochemistry and GMC inventory databases (Source: this report)

   string

   dggs_field_station_number

   The number assigned in the field to uniquely identify the outcrop location and description; station numbers have been modified to DGGS standard format. Generic example of a sample identifier: YYAAA999X: YY=last two digits of the year the sample was collected, AAA=geologist's initials (one to three characters), 999=unique station number. This number is used to identify corresponding records in the DGGS geochemistry and GMC inventory databases (Source: this report)

   string

   latitude_nad27

   Latitude, decimal degrees, NAD27 datum (Source: this report)

   double

   longitude_nad27

   Longitude, decimal degrees, NAD27 datum (Source: this report)

   double

   observer

   Geologist who observed and described the sample (Source: this report)

   string

   observation_date

   The observation date (Source: this report)

   date

   rock_name

   General rock name based on mineral composition and textures (Source: this report)

   string

   thin_section_remarks

   Freeform text written to briefly describe key lithologic features and highlight uncertainties (Source: this report)

   string

   texture_keywords

   Comma delimited list of keywords used to note observed textures (Source: this report)

   string

   texture_remarks

   Freeform text written to briefly describe key texture features and highlight uncertainties (Source: this report)

   string

   matrix_remarks

   Freeform text written to briefly describe matrix/groundmass and highlight uncertainties (Source: this report)

   string

   matrix_size_mm

   The average grain size of the matrix, measured in mm (Source: this report)

   double

   mineralization_flag

   Flag to indicate presence or lack of mineralization features (Source: this report)

   string

   alteration_flag

   Flag to identify rocks that may be too altered for whole rock analysis. 'Undetermined' indicates the rock was altered, but the degree of alteration could not be assigned (Source: this report)

   string

   overprinting_alteration

   Characteristics or mineralogy of overprinting alteration (Source: this report)

   string

   overprinting_structures

   Characteristics of overprinting structures (Source: this report)

   string

   label_error_flag

   Flag to identify samples or records where the thin section label differs from the most likely associated sample and field station. Because there is not an exact match, there is some possibility that the locations for these samples and links to related data may be incorrect (Source: this report)

   string

   bonnifield-tx-mineral-descriptions.csv, bonnifield-tx-mineral-descriptions-metadata.csv

   petrographic thin section mineral observations (Source: Alaska Division of Geological & Geophysical Surveys (DGGS))

   thin_section_id

   The label printed on the thin section slide. Foreign key used to relate mineral observation records to thin section observation records (Source: this report)

   string

   mineral

   Mineral name, NULL values indicate that the observer could not confidently identify the mineral (Source: this report)

   string

   modal_abundance_pct

   Visually estimated modal abundance of mineral (percent) (Source: this report)

   string

   mineral_shape

   Mineral shape (Source: this report)

   string

   mineral_size_mm

   The average size of the mineral, measured in mm (Source: this report)

   double

   mineral_remarks

   Freeform text written to briefly describe key observations and highlight uncertainties (Source: this report)

   string

   tectonic_timing

   Inferred timing of mineral origination relative to tectonic deformation. Inferences are based on foliation, strain shadows, extinction patterns, and other observations (Source: this report)

   string

   mineral_sequence_flag

   Flag to differentiate primary and secondary minerals (Source: this report)

   string

   mineral_replaced

   The primary mineral (or mineral class) that is replaced by the secondary mineral (Source: this report)

   string

   pct_primary_mineral_replaced

   The percentage of the primary mineral that is altered to the secondary mineral (Source: this report)

   double

Who produced the data set?

1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
   • Montayne, Simone
   • Wypych, Alicja
   • Freeman, L.K.
   • Griesel, G.A.

2. Who also contributed to the data set?

   The Eastern Bonnifield Mining District Project is part of the Alaska Airborne Geophysical/Geological Mineral Inventory Program, which was 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, thin section preparation, and geochemical analyses was also provided through the State of Alaska General Fund and the U.S. Geological Survey STATEMAP Program under award number 08HQAG0051.

3. To whom should users address questions about the data?
   Alaska Division of Geological & Geophysical Surveys
   Metadata Manager
   3354 College Road
   Fairbanks, AK 99709-3707
   USA
   

   (907)451-5020 (voice)
   (907)451-5050 (FAX)
   dggspubs@alaska.gov
   

   Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays

Why was the data set created?

Mineral Resources Section personnel from the Alaska Division of Geological & Geophysical Surveys (DGGS) carried out a geologic field mapping survey in the eastern part of the Bonnifield mining district in the Fairbanks A-1 and A-2 and the Healy D-1 and D-2 quadrangles. The map area contains several significant polymetallic sulfide prospects and transects three metamorphic assemblages, which include the Healy Schist, Keevy Peak Formation, and the Totatlanika Schist. The fieldwork (June 16 through July 18, 2008) augments publically available information critical to building an understanding of Alaska's geology and is part of an integrated program of airborne geophysical surveys followed by geologic mapping. Specifically, this mapping provides geologic context for geophysical surveys conducted in 2006 (Burns and others, 2016).

How was the data set created?

1. From what previous works were the data drawn?

2. How were the data generated, processed, and modified?

   Date: 2008 (process 1 of 3)

   Sample collection - Mineral Resources Section personnel from the Alaska Division of Geological &amp; Geophysical Surveys (DGGS) carried out a geologic field mapping survey in the eastern part of the Bonnifield mining district in the Fairbanks A-1 and A-2 and the Healy D-1 and D-2 quadrangles (June 16 through July 18, 2008). The samples selected for petrographic observation either generally represent outcrop lithology or contain significant lithologic features.

   Date: 2008 (process 2 of 3)

   Sample preparation - Thin section billets were cut using a diamond-blade tile saw; foliated and lineated rocks were cut so that the examination surface is perpendicular the rock fabric. Many of the rocks were fragile and required either significant gluing or vacuum impregnation to prepare billets. The billets were used to create standard petrographic thin-sections. Thin section billets were mounted on glass slides, hand ground to 30 microns, and finished with a 600 mesh grit. A few thin sections of mineralized rocks were left uncovered and polished for use in reflected light ore microscopy.

   Date: 2010 (process 3 of 3)

   Petrographic observation - Using basic polarized light microscopy, project staff examined thin sections to identify mineral content, investigate textural relationships, and determine suitability for further geochemical and geochronological analysis. A polarizing reflected light microscope was used on the polished thin sections containing sulfide minerals.

3. What similar or related data should the user be aware of?

   Athey, J.E., Seitz, S.S., and Staff, DGGS, 2017, Geologic Photos of Alaska: Digital Data Series DDS 14, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

   Online Links:

   • <http://doi.org/10.14509/29735>

   Benowitz, J.A., Layer, P.W., and Freeman, L.K., 2011, 40Ar/39Ar ages from the east Bonnifield geologic map area, Fairbanks A-1, Fairbanks A-2, Healy D-1, and Healy D-2 quadrangles, Alaska: Raw Data File RDF 2011-2 v. 1.1, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

   Online Links:

   • <http://doi.org/10.14509/22482>

   Other_Citation_Details: 22 p

   Burns, L.E., Fugro Airborne Surveys Corp., Stevens Exploration Management Corp., Graham, G.R.C., and Emond, A.M., 2016, Bonnifield mining district electromagnetic and magnetic airborne geophysical survey data compilation: Geophysical Report GPR 2016-1, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

   Online Links:

   • <http://doi.org/10.14509/29557>

   Other_Citation_Details: 2 sheets

   Staff, DGGS, 2016, Geologic Materials Center Inventory: Digital Data Series DDS 11, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

   Online Links:

   • <http://doi.org/10.14509/29550>

   Staff, DGGS, Seitz, S.S., Reioux, D.A., Blessington, M.J., Jozwik, Diana, and Mulliken, K.M., 2017, Alaska Geochemistry: Digital Data Series DDS 15, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

   Online Links:

   • <http://doi.org/10.14509/29770>

   Freeman, L.K., Newberry, R.J., Andrew, J.E., Szumigala, D.J., Werdon, M.B., Athey, J.E., and Burns, L.E., 2013, Geologic setting of syngenetic and epigenetic deposits in the eastern Bonnifield mining district, Alaska (presentation): Alaska Miners Association, 22nd Annual Biennial Mining Conference, March 9-13, 2010: Poster and Presentation Freeman, L.K. and others, 2013, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

   Online Links:

   • <http://doi.org/10.14509/25279>

   Other_Citation_Details: 25 p

   Freeman, L.K., Newberry, R.J., Werdon, M.B., Szumigala, D.J., Andrew, J.E., and Athey, J.E., 2016, Preliminary bedrock geologic map data for the eastern Bonnifield mining district, Fairbanks and Healy quadrangles, Alaska: Preliminary Interpretive Report PIR 2016-3, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

   Online Links:

   • <http://doi.org/10.14509/29661>

   Other_Citation_Details: 6 p

   Freeman, L.K., Werdon, M.B., Szumigala, D.J., Andrew, J.E., Newberry, R.J., and Athey, J.E., 2009, Geochemical, major-oxide, minor-oxide, trace-element and carbon data from rocks collected in 2008 in the eastern Bonnifield mining district, Fairbanks and Healy quadrangles, Alaska: Raw Data File RDF 2009-1 v. 1.2, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

   Online Links:

   • <http://doi.org/10.14509/20041>

   Other_Citation_Details: 69 p

How reliable are the data; what problems remain in the data set?

1. How well have the observations been checked?

   This publication is PRELIMINARY in nature and meant to allow release of field observations and initial interpretations of geologic features. It has undergone limited technical review but does not necessarily conform to DGGS editorial standards. Interpretations contained in this publication are subject to change. Observations in the data tables include lithologic classification, texture, mineral crystal structure and development sequence, and mineral components. Mineral and component modal percentages are visual estimates. The primary focus of this work was to aid in distinguishing igneous, volcaniclastic metasedimentary rocks, and volcaniclastic metavolcanic rocks, consequently the level of detail varies from cursory to comprehensive. Although the classifications and descriptions have been lightly edited for spelling and consistency, the descriptions are typically freeform text written to note key features and highlight uncertainties that may warrant subsequent investigation. Users may notice sample numbering discrepancies throughout various Bonnifield Project publications. DGGS staff have completed significant work over the duration of the project to assimilate data from various sources into comprehensive division-wide databases. In conjunction with loading the Bonnifield data into the Geologic Materials Center Inventory and Alaska Geochemistry databases, staff identified and, when possible, corrected sample labeling inconsistencies. Error correction required certain assumptions, and it is possible, particularly in cases where multiple lithologies were collected from a single outcrop, that published geochemical results and thin section observations tied to a given sample number may not correspond to the same rock. The data tables in this publication list both the sample numbers written on each thin section and the standardized numbers used by the division databases.

2. How accurate are the geographic locations?

   Location coordinates were collected using hand-held GPS units (no differential correction was applied). Estimated position errors calculated by the GPS units were a minimum of 3 meters. At many locations the horizon was limited by steep topography, resulting in positional errors of more than 100 meters. Waypoints were downloaded from the GPS units into the project database, merged with related information, and converted from UTM (Universal Transverse Mercator) to geographic coordinates. Location coordinates are based on the NAD27 datum (North American Datum of 1927).

3. How accurate are the heights or depths?

4. Where are the gaps in the data? What is missing?

   This data release is complete.

5. How consistent are the relationships among the observations, including topology?

   not applicable

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints:

This report, map, and/or dataset is available directly from the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (see contact information below).

Use_Constraints:

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. The 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. The State of Alaska makes no express or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data 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 or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product.

1. Who distributes the data set? (Distributor 1 of 1)
   Alaska Division of Geological & Geophysical Surveys
   Metadata Manager
   3354 College Road
   Fairbanks, AK 99709-3707
   USA
   

   (907)451-5020 (voice)
   (907)451-5050 (FAX)
   dggspubs@alaska.gov
   

   Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays

2. What's the catalog number I need to order this data set?

   RDF 2019-1

3. What legal disclaimers am I supposed to read?

   The State of Alaska makes no expressed or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data 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 or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product.

4. How can I download or order the data?
   • Availability in non-digital form:

     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 by mail, phone, fax, or email from the DGGS Fairbanks office. 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. Turnaround 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 the exact shipping amount.

   • Cost to order the data: Contact DGGS for current pricing

   • Availability in digital form:

     Data format:	report and digital data
     Network links:	<http://doi.org/10.14509/30171>

   • Cost to order the data: Free download

Who wrote the metadata?

Dates:

Last modified: 08-Apr-2019

Metadata author:

Alaska Division of Geological & Geophysical Surveys
Attn: Simone Montayne
Metadata Manager
3354 College Road
Fairbanks, AK 99709-3707
USA

(907)451-5020 (voice)
(907)451-5050 (FAX)
dggspubs@alaska.gov

Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays

Metadata standard:

FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

Metadata extensions used:

• <http://www.dggs.alaska.gov/metadata/dggs.ext>