Interpretation of Exploration Geochemical Data for the Mount Katmai Quadrangle and Adjacent Parts of the Afognak and Naknek Quadrangles, Alaska By S.E. Church, J.R. Riehle, and R.J. Goldfarb U.S. GEOLOGICAL SURVEY BULLETIN 2020 Descriptive and interpretive supporting data for the mineral resource assessn~entof this Alaska Mineral Resource Assessnzent Program (AMRAP) study area UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1994 U.S. DEPARTMENT OF THE INTERIOR BRUCE BABBITT, Secretary U.S. GEOLOGICAL SURVEY Gordon P. Eaton, Director For Sale by U.S. Geological Survey, Map Distribution Box 25286, MS 306, Federal Center Denver, CO 80225 Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government. Library of Congress Cataloging-in-PublieatlonData Church, S.E. Interpretation of exploration geochemical data for the Mount Katmai quadrangle and adjacent parts of the Afognak and Nalrnek quadrangles, Alaska 1 by S.E. Church, J.R. Riehle, and R.J. Goldfarb. p. cm. - (U.S. Geological Survey bulletin ;2020) Includes bibliographical references. Supt. of Docs. no. : 119.3 :2020 1. Mines and mineral resources-Alaska. 2. Mining gedogy- Alaska 3. Geochemical prospecting-Alaska I. Riehle, J.R. 11. Goldfarb, R.J. UI. Title. IV. Series. QE75.B9 no. 2020 [TN24.A4] 557.3 5420 93-2012 [553'.09798] CIP CONTENTS Abstract ............................................................................................................................. Introduction....................................................................................................................... Geologic Setting ..................................................................................................... Geology of the Katmai Study Area .................................................................................. Paleozoic(?) and Early Mesozoic Rocks ............................................................... Mesozoic Rocks ..................................................................................................... Tertiary Rocks ........................................................................................................ Quaternary Rocks and Deposits .............................................................................. Structural Geology ................................................................................................. Mineral Exploration ............................................................................................... Known Mineral Occurrences on the Alaska Peninsula and in the Area North of the Katmai Study Area ....................................................................................................... Mineral Occurrences Associated with Pre-Jurassic Rocks and Pre-Batholithic Rocks .................................................................................................................. Mineral Occurrences Associated with Late Cretaceous to Middle Tertiary Plutonic Rocks of the Alaska-Aleutian Range Batholith ................................... Mineral Occurrences Associated with Tertiary and Quaternary Volcanic Arc Rocks ........................................................................................................... Exploration Geochemistry ................................................................................................ Sample and Data Collection ................................................................................... Discussion of the Reconnaissance Geochemical Data ........................................... Discussion of the Rock Geochemical Data ............................................................ Factor Analysis of the Reconnaissance Geochemical Data .................................... Geologic Evaluation of the Factor-Analysis Solutions .......................................... Geologic Interpretation ..................................................................................................... Area North of Naknek Lake ................................................................................... Area South of Naknek Lake and West of the Bruin Bay Fault ............................. Kulik Lake Area ..................................................................................................... Buttress Range-lkagluik Creek Area ..................................................................... Mount Katolinat Subarea .................................................................................. Buttress Range Subarea .................................................................................... Ikagluik Creek Subarea..................................................................................... Quaternary Volcanic Rocks of the Aleutian Range Subarea ............................ Fourpeaked Mountain Area .................................................................................... Ninagiak River Area ............................................................................................... Barrier Range-Kukak Bay Area ............................................................................. Kukak Bay Subarea .......................................................................................... Kuliak Bay-Katmai River Subarea .................................................................. Katmai Lakes-Hagelbargers Pass-Dakavak Lake Subarea ............................. Kejulik Mountains Area ......................................................................................... Summary........................................................................................................................... References Cited ............................................................................................................... PLATES plates are in pocket] Map of the Mount Katmai quadrangle and adjacent parts of the Afognak and Naknek quadrangles. Alaska. showing geochemical data indicating undiscovered porphyry-copper deposits IV CONTENTS 2 . Map of the Mount Katmai quadrangle and adjacent parts of the Afognak and Naknek quadrangles. Alaska. showing geochemical data indicating undiscovered base-metal-bearing polymetallic veins 3 . Map of the Mount Katmai quadrangle and adjacent parts of the Afognak and Naknek quadrangles. Alaska. showing geochemical data indicating undiscovered precious-metal-bearing polymetallic and epithermal quartz veins FIGURES 1. Index map of the Alaska Peninsula showing the location of the Katmai study area ............................................ 2 . Generalized geologic map of the Mount Katmai. western Afognak. and eastern Naknek quadrangles .............. 3 . Boxplot of geochemical data for stream-sediment samples from the Katmai study area ..................................... 4 . Log plot of range in concentration of geometric means and 95th percentiles of elements in selected lithologic groups from the Katmai study area ....................................................................................................................... 5-10 . Maps of the Katmai study area showing: 5. Distribution of sedimentary barite and its correlation with Jurassic and Cretaceous rocks .......................... 6. Correlation of high aqua-regia-leachate factor 4 sample-scores with zones of altered rocks ....................... 7 . Distribution of localities for which stream-sediment factor 2 sample-scores are high ................................. 8 . Distribution of localities for which heavy-mineral-concentrate factor 1 sample-scores are high ................. 9 . Distribution of localities for which aqua-regia-leachate factor 3 sample-scores are high ............................ 10. Mineral occurrences and eight major areas favorable for undiscovered mineral deposits ............................ TABLES Summary of emission spectrographic data for stream-sediment samples............................................................. 12 Summary of aqua-regia-leachate data for stream-sediment samples .................................................................... 14 Summary of emission spectrographic data for nonmagnetic heavy-mineral concentrates from stream sediments.............................................................................................................................................................. 15 Summary of geometric means and the 95th and 98th percentiles of individual element distributions for seven lithologic groups .................................................................................................................................................... 16 Factor loadings for the first five factors after varimax rotation of the stream-sediment data ............................... 19 Factor loadings for the first four factors after varimax rotation of the data for aqua-regia leachates from stream sediments ...................................................................................................................................................19 Factor loadings for the first four factors from the nonmagnetic heavy-mineral-concentratedata using an extreme-variable solution .................................................................................................................................20 Summary of threshold values used for rock and float samples for porphyry Cu deposits ....................................pl . 1 Summary of threshold values used for rock and float samples