| of a Part of the Harcuvar | Mountains Wilderness Study Area (AZ-020-075), | La Paz County, Arizona I I tI "'1 rI I i MINERAL RESOURCES OF A PART OF THE HARCUVAR MOUNTAINS WILDERNESS STUDY AREA (AZ-020-075), LA PAZ COUNTY, ARIZONA I I I I by ,I Steven E. Tuftin RECE~\/FO ,I MLA 29-88 1988 JUL 2 2 t988 I p, r - I Intermountain Field Operations Center I Denver, Colorado I I UNITED STATES DEPARTMENT OF THE INTERIOR I Donald P. Hodel, Secretary BUREAU OF MINES I TS Ary, Director I illi PREFACE I The Federal Land Policy and Management Act of 1976 (Public Law 94-5?9) requires the U.S. Geological Survey and the U.S. Bureau of Mines to conduct I mineral surveys on certain areas to determine mineral values, if any, that may be present. Results must be made available to the public and be submitted to I the President and the Congress. This report presents the results of a mineral I survey of a part of the Harcuvar Mountains Wilderness Study Area (AZ-020-075), La Paz County, Arizona. I I I I i il FII This open-file report summarizes the results of a Bureau of Mines wilderness study. The report is preliminary and has not been edited or reviewed for conformity with the Bureau of Mines editorial standards. This study was conducted by personnel from the Branch of Mineral Land Assessment (MLA), Intermountain Field Operations Center, P.O. Box 250B6, Denver Federal Center, Denver, CO B0225. I CONTENTS I Page Summary .................................................................. 1 I Introduction ......... r ................................................... 2 Geographic setting .................................................. 3 I Previous studies .................................................... 3 I Methods of investigation ............................................ 3 Geologic setting .................................................... 5 I Mining activity .......................................................... 5 Oil and gas .............................................................. 6 I Appraisal of sites examined.............................................. 6 I Webber Mine area .................................................... 8 Happy Camp Canyon area .............................................. 9 I Miscellaneous occurrences ........................................... II Conclusions .............................................................. II I References ............................................................... 13 Appendix--Results and lower detection limits of multi-element analysis I for selected samples ........................................... 20 ILLUSTRATIONS I Plate I. Mine and prospect map of the Harcuvar Mountains study at area, La Paz County, Arizona ................................ back I EXPLANATION OF SYMBOLS FOR FIGURES 3-5 ............................. 14 I Figure 1. Index map of the Harcuvar Mountains study area, La Paz County, Arizona ............................................. Map showing oil and gas leases and lease applications within I and near the Harcuvar Mountains study area, La Paz County, Arizona ..................................................... I I ii I ii ¸:, ILLUSTRATIONS--Continued I Page Figure. 3A. Map of the Webber Mine area................................. 15 I 3B. Plan and longitudinal section of the Webber adit ............ 16 4. Plan map and longitudinal section of the western adit and I prospects in Happy Camp Canyon.............................. 17 . Map of the eastern adit and prospects, Happy Camp Canyon.... 18 I TABLES Table I. Data for samples from miscellaneous prospects in and near I the Harcuvar Mountains study area........................... 19 l UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT I ° degree ft foot I in. inch I mi mile ppm part per million I % percent I oz/st troy ounce per short ton I i I I I iii I MINERAL RESOURCES OF A PART OF THE HARCUVAR MOUNTAINS WILDERNESS STUDY AREA (AZ-020-075), LA PAZ COUNTY, ARIZONA I by I Steven E. Tuftin, U.S. Bureau of Mines SUMMARY I In January 1987, the Bureau of Mines conducted a mineral investigation of 25,28? acres of the ?4,?78 acre Harcuvar Mountains Wilderness Study Area, in i La Paz County, Arizona, on land administered by the Bureau of Land Management. The Bureau of Mines studied that part of the Wilderness Study I Area deemed preliminarily suitable for inclusion in the National Wilderness i Preservation System. The mineral investigation was requested by the Bureau of Land Management and authorized by the Federal Land Policy and Management Act I of 1976 (Public Law 94-5?9). The Harcuvar Mountains are composed of metamorphic and granitic rocks of i Precambrian and Cretaceous age. Mineralized faults in granite gneiss in the I central and eastern parts of the study area are exposed in several prospects and small mines. Prospects and a small adit included in the Webber Mine, in I the central part of the study area, are on a northwest-striking fault in gneiss. An inferred subeconomic resource of 600 tons of 3.3% copper has been i determined for the Webber adit, and an inferred subeconomic resource of 8,000 I tons of 1.8% copper has been determined for the Webber Mine area. Workings along Happy Camp Canyon, inside the eastern border of the study area, are on i three northwest-trending faults. A mine and prospect on the western fault are on a vuggy quartz vein with gold concentrations varying from 0.011-.073 I oz/st. An inferred subeconomic resource of 300 tons of 0.045 oz gold/st and I 1.15% copper, and an inferred subeconomic resource of 2,000 tons of 0.030 oz I I I gold/st and 1.15% copper has been determined for this structure. Several I million tons of ore would be needed to make these resources economical. The veins and mineralized faults in the vicinity of the workings in I Webber Canyon and Happy Camp Canyon area are oxidized. There may be a zone of secondary copper enrichment at depth. The mineralized fault-zones and veins I are generally less than 2 ft thick. i One mile west of the study area, a sample from the dump of a shaft in Tertiary-age sedimentary rock contains a gold concentration of 0.051 oz/st, I and 0.26% copper. A sample from another prospect in the Tertiary strata has a much lower concentration of copper. This strata is in the upper plate of a I detachment fault and does not occur in the study area. I INTRODUCTION In January 19B7, the Bureau of Mines, in a cooperative program with the I U.S. Geological Survey (USGS), studied the mineral resoures of a part of the Harcuvar Mountains Wilderness Study Area (WSA), La Paz County, Arizona, on I lands administered by the Bureau of Land Management (BLM), Phoenix District I Office. The Harcuvar Mountains WSA comprises 74,778 acres; the Bureau studied the 25,2B7 acres deemed preliminarily suitable for inclusion in the National I Wilderness Preservation System. "Study area" as used in this report, refers only to the smaller area. The Bureau surveys and studies mines, prospects, I and mineralized areas to appraise reserves and identified subeconomic i resources. The USGS assesses the potential for undiscovered mineral resources based on regional geological, geochemical, and geophysical surveys. This I report presents the results of the Bureau of Mines study which was completed prior to the USGS investigation. The USGS will publish the results of its I studies. A joint USGS-Bureau report, to be published by the USGS, will I integrate and summarize the results of both surveys. 2 I Geographic setting The study area is about 11 mi long and 4 mi wide and includes a rugged segment of the northeast-trending Harcuvar Mountains in the Basin and Range physiographic province. Butler Valley lies to the northwest and McMullen Valley lies to the southeast of these mountains. In the study area, the peaks and ridges along the crest of the range are about 4,600-4,900 ft in elevation, rising about 2,800 ft above the valley floor. The highest point in the study area is 4,957 ft in the northeast corner near Smith Peak. The southwest corner of the study area lies about 9 mi north of Nenden, and about 1.5 mi east of Cunningham Pass (fig. 1). Access to the area is by secondary gravel and dirt roads off the paved Cunningham Pass road. Previous studies The regional geology of west-central Arizona is summarized by Reynolds (1980), who describes the Late Cretaceous-Tertiary metamorphic and igneous complexes that include the Harcuvar Mountains. Mesozoic structural features in the region are described by Reynolds and others (1986). A model for hydrothermal mineralization as related to detachment faults is discussed by Wilkins and others (1986). Structural controls of mineralization associated with Tertiary detachment faults are described by Spencer and Welty (1986). The Bullard detachment fault in the far eastern part of the Harcuvar Mountains is described by Reynolds and Spencer (1985). Metallic mineral districts in the region are summarized by Keith and others (1983). Methods of investigation Prior to field work, a literature search was conducted for minerals information pertinent to the study area. Bureau of Land Management records were checked for current mining claims and oil and gas leases. Two Bureau geologists conducted a five-day field examination of the study area. 3 R. IO W. R. 13 W. R. 12 W. 113°30 ' R. II W. 113°20 ' I q¢' 9 I Ill ^ BLACK BUTTE ~ I % N. NTAINS e ~ ° . 34000 ' 'mI. ;. 0 i T. 7 N. I - PEA/(" : ~ t,I I 4619ff = ~ ~ r., I "1". I 6 N. i 3'3050 ' -- 33o50' Wenden~ J 113 30' 113°?-0' L / 0 5 IOmi / I"-"---"'1 ~ P--'----'--I I"-'-'-'-I ~ I EXPLANATION ==~=== U.S. HIGHWAY - N- / PAVED ROAD SECONDARY GRAVEL OR DIRT ROAD MAP LOCATION Figure 1.--Index map of the Harcuvar Mountains study area, La Paz County, Arizona. 4 | Twenty-five chip and dump samples were collected from mines and prospects I in and near the study area. Gold concentrations were determined by fire assay with .an atomic absorption spectrometry finish; silver and copper I concentrations were determined by atomic absorption spectrometry. Five of these samples were selected for multi-element analyses by inductively coupled I plasma-atomic emission spectrometry (appendix).