Western Washington University Western CEDAR WWU Graduate School Collection WWU Graduate and Undergraduate Scholarship Fall 1986 Genesis of Gold Mineralization in the Lone Jack Mine Area, Mt. Baker Mining District, Washington Lief G. Christenson Western Washington University Follow this and additional works at: https://cedar.wwu.edu/wwuet Part of the Geology Commons Recommended Citation Christenson, Lief G., "Genesis of Gold Mineralization in the Lone Jack Mine Area, Mt. Baker Mining District, Washington" (1986). WWU Graduate School Collection. 774. https://cedar.wwu.edu/wwuet/774 This Masters Thesis is brought to you for free and open access by the WWU Graduate and Undergraduate Scholarship at Western CEDAR. It has been accepted for inclusion in WWU Graduate School Collection by an authorized administrator of Western CEDAR. For more information, please contact [email protected]. GENESIS OF GOID MINERALIZATH o ^ IN THE LONE JACK MINE AREA, m. BAKER MINING DISTRICT, WASHINGOm 4 L» I ' A Thesis Presented tb the Faculty of Western Washingljon tfeiversity In Partial Fulfillment 'I of the Requirements for the Degree .. Master of Science ft ft by Lief G. Christenson November, 1986 GENESIS OF GOLD MINERALIZATION IN THE LONE JACK MINE AREA, MT. BAKER MINING DISTRICT, WASHINGTON by Lief G. Christenson Accepted in Partial Conpletion of the Requirements for the Degree Master of Science ^ ^h( Dean of Graduate ool ADVISORY CCNMITTEE Chairman A MASTER'S THESIS In presenting this thesis in partial fulfillment of the requirements for a master's degree at Western Washington University, I grant to Western Washington University the non-exclusive royalty-free right to archive, reproduce, distribute, and display the thesis in any and all forms, including electronic format, via any digital library mechanisms maintained by WWU. I represent and warrant this is my original work and does not infringe or violate any rights of others. I warrant that I have obtained written permissions from the owner of any third party copyrighted material included in these files. I acknowledge that I retain ownership rights to the copyright of this work, including but not limited to the right tojjse all or part of this work in future works, such as articles or books. Library users are granted permission for individual, research and non-commercial reproduction of this work for educational purposes only. Any further digital posting of this document requires specific permission from the author. Any copying or publication of this thesis for commercial purposes, or for financial gain, is not allowed without my written permission. Name: Signature: WESTERN WASHINGTON UNIVERSITY Bellingham, Washington 98225 • [206] 676-3000 Master's Thesis In presenting this thesis in partial fulfil Iment of the requirements for a Master's degree at Western Washington University, I agree that the Library shall make its cxopies freely available for inspection. I further agree that extensive copying of this thesis is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this thesis for commercial purposes, or for financial gain, shal 1 not be allowed without my written permission. Signed; Date: November 10, 1986 ABSTRACT The Lone Jack group of claims is in the Mt. Baker Mining District, northern Whatcom County, Washington. Three prominent gold-quartz veins are present, two of v^ich were mined and produced 945 kg of gold between 1901 and 1924. Since then mining operations have not been renewed. The quartz veins are within 3 km of surface exposures of the Miocene Chilliwack Batholith, above and within a zone of deformation related to the mid-Late Cretaceous Shuksan fault. This major Northern Cascades structure has juxtaposed the Upper Mesozoic Carrington Phyl lite over the Paleozoic volcanic and sedimentary rocks of the Chilliwack Group. The quartz veins are genetically related to local Tertiary block faulting v^ich postdated the metamorphism and deformation related to the Shuksan fault. The style of deformation and timing of these Tertiary faults suggests that they are related to the emplacement of the nearby batholith. The quartz veins were emplaced during, perhaps in the waning stages of, this intrusive activity. Two generations of mineralization are present; each has a similar paragenesis. Vein minerals other than quartz include pyrrhotite, pyrite, chalcopyrite, tel lurbismuth, and free gold. Gold was deposited in equilibrium with pyrrhotite, sericite, and graphite. Fluid inclusion analyses were used to determine that the ore-forming solutions were boiling, dilute, and contained an average of 0.25 mol% CO2. Crystallization occurred at about 285*^C and 625 bars of lithostatic pressure. Thermodynamic calculations indicate that the gold may have been transported as the Au(HS )2 complex, and that precipitation of the gold resulted from the physiochemical changes caused by boiling. i Prospecting for similar deposits in the area should be directed toward locating post-metamorphic quartz veins near the Shuksan fault and the Cliilliwack Batholith, v^ich show evidence of boiling. 11 ACKNOWLEDGEMENTS I am indebted to a number of people who provided physical, mental, and patient support during the course of my studies on the Lone Jack property. In particular. Dr. Antoni Wodzicki's enthusiastic support and guidance is here grateful ly acknowledged. Dr. R. Scott Babcock introduced me to the project and provided an excellent critical review of the manu­ script- I am also indebted to Dr. Edwin Brown for his critical review and for discussions on the geology of the study area. Dr. Steven Aronoff provided helpful editorial comments. Jim Sevigny, Bill Harrison, and Dave Blackwell from W.W.U. found time to accompany me in the field and helped lug out rock samples. George Mustoe helped familiarize me with lab equipment and also showed me the Lone Jack property for the first time. Patty Combs, the most competent and friendly secretary in the world, helped me get through the maze of office machinery and did seme fancy last-minute typing on the manuscript. I am indebted to Peter Jewett, Chuck Ziegler, Jeff Jones, and David Silverberg for helpful discussions on the geology of the North Cascades. My family all chipped in —brother John lent his jeep and helped carry samples; sister Karen housed me in my early days at Western, and my father. Dr. Earl Christenson, provided financial and motivational support. The hardest acknowledgment to write is the debt I owe to my wife, Kathryn. She deserves co-authorship for the support she has provided, and I don't think anyone else is quite as happy to see this project terminated. We did it, Kate! Ill TABLE OF CONTENTS Page Abstract i Acknowledgements iii List of Figures v INTPODUCTIdJ 1 Location and Topograj^y 1 Previous Work 1 Mining History 4 Scope of Present Study 5 RBGICNAL CTDLOGY 6 CTDLOGY OF THE imE JACK CLAIMS 9 Lithologic Units 9 Structure 16 Faulting 16 Folding 18 GEOLOGY OF THE ORE BODIES 22 Lulu 22 Lone Jack 24 Whist 25 Lode Vein Mineralogy and Paragenesis 25 Economic Geology 30 FLUID INCLUSICN STUDIES 35 Selection and Sample Preparation 35 Description of Fluid Inclusions 36 Heating and Freezing Measurements 39 Results of Fluid Inclusion Studies 55 CCNDITICNS OF MINERALIZATIC»^ 61 Thermodynamic Equilibria 61 Gold Transport and Deposition 64 Summation of Mineralizing Conditions 68 DISCUSSIcaJ 69 Model for Gold Deposition 70 Prospecting 72 CCMXUSIONS 75 REFERENCES CITED 76 APPENDIX 1. Fluid Inclusion Data 82 APPENDIX 2. Selected Equilibrium Constants 87 iv LIST OF FIGURES Figijre Page 1 Location map of the Lone Jack mine 2 2 Claim boundaries of the Lone Jack mine 3 3 StratigrajAiy of the North Cascades 7 4 Geologic map of the Goat Mountina-Tcxni^ioi Peak area 10 5 Geologic map of the Lone Jack claims 11 6 Cross-sections A-A' and B-B' 12 7 Photomicrograph of Barrington Phyllite 14 8 Photomicrograph of hornfelsed Barrington Phyllite 14 9 Geologic cross-section through Swamp Creek 17 10 Lower hemisphere stereonet plot of fold axes in the Barrington Phyllite 21 11 Photograph of Lone Jack stope 23 12 Photomicrograph of Whist vein wall rock 26 13 Photonicrograph of pyrrhotite replacing pyrite 28 14 PhotOTiicrograph of chalcopyrite replacing pyrrhotite 28 15 Photomicrograph of tellurbismuth and gold 29 16 Photonicrograph of Lone Jack wall rock 31 17 Paragenetic sequence of vein mineralization 32 18 Photomicrograph of three-phase fluid inclusion 37 19 CO2 melting temperature diagram 39 20 T-P phase equilibria diagram for CO2-CH4 41 21 CO2-CH4 determination diagram 42 22 H2O melting temperature diagram 43 23 Bepression of melting temperature of clathrate and H2O by NaCl 45 V 24 Clathrate melting temperature diagram 46 25 CD2 hcancgenization temperature diagram 48 26 P-T phase equilibria for CO2 49 27 p-^ diagram for CO2 and H2O 50 28 Vg-XH20 diagram 51 29 Calculated mole fraction H2O diagram 53 30 Fluid inclusion homogenization diagram 54 31 Isocompositional cnarves for H2O-CO2 56 32 Isocompositional curves for H20-C02-NaCl 57 33 Photomicrograph of fluid inclusions fron secondary quartz 58 34 Geothermal gradient infered fron mineralizing conditions 60 35 f02“pH conditions of mineralization 63 36 pH determination diagram 65 37 Sketch map of gold-quartz veins within 3 km of the Lone Jack mine 73 VI 1 INTRODUCTION The Lone Jack Mine is located in northern Whatcom County, Washington, within the Mt. Baker mining district. Between 1900 and 1924, 945 kg of gold were recovered from these claims from gold, silver, and tellurium bearing quartz veins. This study contributes to the understanding of the orgin of such gold-quartz veins, through analysis of the physical and chemical controls governing these deposits. Location and Topography The Lone Jack mine consists of five patented and eleven unpatented claims located in sections 22 and 23, T40N, R9E, northern Whatcom County, Washington (figures 1 and 2).