UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY Analytical results and sample locality map of stream-sediment, heavy-mineral-concentrate, rock, and soil samples from the Whipple Mountains Wilderness Study Area (CDCA-312) and Whipple Mountains Addition Wilderness Study Area (AZ-050-010), San Bemardino County, California By M. S. Erickson , S. P. Marsh , D. E. Detra , and B. F. Arbogast Open-File Report 87-631 This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards and stratigraphic nomenclature. Any use of trade names is for descriptive purposes only and does not imply endorsement by the USGS. *U.S. Geological Survey, DFC, Box 25046, MS 973, Denver, CO 80225 1987
Transcript
UNITED STATES DEPARTMENT OF THE INTERIOR
GEOLOGICAL SURVEY
Analytical results and sample locality map
of stream-sediment, heavy-mineral-concentrate, rock, and soil samples
from the Whipple Mountains Wilderness Study Area (CDCA-312) and
Whipple Mountains Addition Wilderness Study Area (AZ-050-010),
San Bemardino County, California
By
M. S. Erickson , S. P. Marsh ,
D. E. Detra , and B. F. Arbogast
Open-File Report 87-631
This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards and stratigraphic nomenclature. Any use of trade names is for descriptive purposes only and does not imply endorsement by the USGS.
*U.S. Geological Survey, DFC, Box 25046, MS 973, Denver, CO 80225
1987
CONTENTS
Page
Studies Related to Wilderness ............................................ 1Introduction.............................................................. 1Methods of Study.......................................................... 1
Samp!e Medi a......................................................... 1Sample Collection.................................................... 3
Stream-sediment samples......................................... 3Heavy-mineral-concentrate samples............................... 3Rock and soil samples........................................... 3
Rock Analysis Storage System (RASS)....................................... 4Description of Data Tables................................................ 5References Cited.......................................................... 5
ILLUSTRATIONS
Figure 1. Location and generalized geology of the Whipple Mountains Wilderness Study Area (CDCA-312) and Whipple Mountains Addition Wilderness Study Area (AZ-050-010), San Bernardino County, Cali forni a........................................................... 2
Plate 1. Map showing geology and locations for stream sediment, panned concentrate, rock, and soil samples in the Whipple Mountains Wilderness Study Area and Whipple Mountains Addition Wilderness Study Area (AZ-050-010), San Bernardino County, California.....in pocket
TABLES
Table 1. Limits of determination for Spectrographic analysis ofrocks and stream sediments........................................... 7
Table 2. Chemical methods used........................................... 8
Table 3. Results of analyses of stream-sediment samples.................. 9
Table 4. Results of analyses of heavy-mineral-concentrate samples........ 21
Table 5. Results of analyses of rock and soil samples.................... 34
STUDIES RELATED TO WILDERNESS
Bureau of Land Management Wilderness Study Areas
The Federal Land Policy and Management Act (Public Law 94-579, October 21, 1976) requires the U.S. Geological Survey and the U.S. Bureau of Mines to conduct mineral surveys on certain areas to determine their mineral values, if any. Results must be made available to the public and be submitted to the President and the Congress. This report presents the results of a geochemical survey of the Whipple Mountains Wilderness Study Area, California Desert Conservation Area and Whipple Mountains Addition Wilderness Study Area, San Bernardino County, California.
INTRODUCTION
In 1980, the U.S. Geological Survey conducted a reconnaissance geochemical survey of the Whipple Mountains Wilderness Study Area, San Bernardino County, California. Approximately 77,000 acres were sampled. This included 75,841 acres of the Whipple Mountains Wilderness Study Area as well as an additional 1,385 acres adjacent in the Whipple Mountains Addition Wilderness Study Area (fig. 1).
The Whipple Mountains Wilderness Study Area is located in the southeast corner of San Bernardino County, California, and lies about 6 mi northwest of Parker, Arizona, and 10 mi southwest of Lake Havasu City, Arizona. Access to the study area is provided on the south by California Street and Highway 62, and on the west side of the Colorado River by a paved road.
The Whipple Mountains Wilderness Study Area is situated in the geologically complex region just west of the California-Arizona border, northwest of Parker, Arizona. The Whipple Mountains consist primarily of a metamorphic basement or core complex overlain on the Whipple Mountains detachment fault by unmetamorphosed Tertiary volcanic and sedimentary rocks. This detachment fault separates the lower plate metamorphic domal core of the Whipple Mountains from the Tertiary upper plate rocks exposed around the flanks. The core complex has been intruded by Cretaceous and Tertiary Plutonic sheets and dikes, which are associated with mineralization in many areas of lower plate rocks. Detachment and normal faulting occurred in the Miocene and resulted in mobilization and redistribution of mineralization into upper plate rocks. Numerous studies have investigated the geology of the Whipple Mountains (Anderson and others, 1979; Carr and others, 1980; Dickey and others, 1980; Frost, 1980; Davis and others, 1980, 1982a; Anderson and Frost, 1981; Anderson and Rowley, 1981; Carr, 1981; and Anderson, 1981). The geology and description of map units are shown on plate 1.
The topographic relief in the area is about 3,000 feet rising to a maximum elevation of 4,131 feet in the central part of the area. The area is rugged with sloping flanks to the south and precipitous faces in the metamorphic core complex to the north. Several large northeast-trending canyons cut into the area from the north.
METHODS OF STUDY
Sample Media
Analyses of the stream-sediment samples represent the chemistry of the rock material eroded from the drainage basin upstream from each sample site.
34°30' 114°30'
EXPLANATIONu';$j Tertiary volcantci and scdnTMntary roclu.
undivided
E^KO^J Crctacaout yanlttc roclu
I mu I Cretaceous 5 and Pioteroioic rnyionltfc: rocks
C pCgi fl ProteroAJic granuoid roclu and gntttt
Prot«rozotc gneiss and Tcntary and Cretacwut dtk*s
FAULT
JL. WHIPPli MOUNTAINS THRUST FAULT
--{- ANTICLINE
SYNCUNEApproximate Bound*y 01 Whipple Mounlami
dernes* Study Ar ICOCA312)
T10 KILOMETERS
Figure 1. Location map and generalized geology of the Whipple Mountains Wilderness Study Area (COCA-312) and Whipple Mountains Addition Wilderness Study Area (AZ-050-010), San Bernardino County. California,
Such information is useful in identifying those basins which contain concentrations of elements that may be related to mineral deposits. Heavy-mineral-concentrate samples provide information about the chemistry of certain minerals in rock material eroded from the drainage basin upstream from each sample site. The selective concentration of minerals, many of which may be ore related, permits determination of some elements that are not easily detected in stream-sediment samples.
Analyses of unaltered or unmineralized rock samples provide background geochemical data for individual rock units. On the other hand, analyses of altered or mineralized rocks, where present, may provide useful geochemical information about the major- and trace-element assemblages associated with a mineralizing system.
Sample Collection
Samples were collected at 154 sites (see fig. 1 and plate 1). At nearly all of those sites, both a stream-sediment sample and a heavy-mineral- concentrate sample were collected. In addition, 45 rock and 5 soil samples were taken, average sampling density was about one sample site per square mile for the stream sediments and heavy-mineral concentrates. The area of the drainage basins sampled ranged from 1 mi^ to 5 mi .
Stream-sediment samples
The stream-sediment samples consisted of active alluvium collected primarily from first-order (unbranched) and second-order (below the junction of two first-order) streams as shown on USGS topographic maps (scale = 1:24,000). Each sample was composited from several localities that may extend as much as 10 ft from the site plotted on the map.
Heavy-mineral-concentrate samples
Heavy-mineral-concentrate samples were collected from the same active alluvium as the stream-sediment samples. Each bulk sample was screened with a 2.0-mm (10-mesh) screen to remove the coarse material. The less than 2.0-mm fraction was panned until most of the quartz, feldspar, organic material, and clay-sized material were removed.
Rock samples
Rock samples were collected from outcrops or exposures at locations shown on plate 1. Samples were collected from areas of hydrothermal or iron oxide alteration and from selected mining areas.
Soil samples
Soil samples were collected from areas of hydrothermal or iron oxide alteration to supplement rock samples taken from these areas.
Sample Preparation
The stream-sediment and soil samples were air dried, then sieved using 80-mesh (0.17-mm) stainless-steel sieves. The portion of the sediment passing through the sieve was saved for analysis.
After the samples were air dried, bromoform (specific gravity 2.8) was used to remove the remaining quartz and feldspar from the heavy-mineral- concentrate samples that had been panned in the field. The resultant heavy- mineral sample was separated into three fractions using a large electromagnet (in this case a modified Frantz Isodynamic Separator). The most magnetic material, primarily magnetite, was not analyzed. The second fraction, largely ferromagnesian silicates and iron oxides, was saved for analysis/archival storage. The third fraction (the least magnetic material which may include the nonmagnetic ore minerals, zircon, sphene, etc.) was split using a Jones splitter. One split was hand ground for spectrographic analysis; the other split was saved for mineralogical analysis. These magnetic separates are the same separates that would be produced by using a Frantz Isodynamic Separator set at a slope of 15° and a tilt of 10° with a current of 0.2 ampere to remove the magnetite and ilmenite, and a current of 0.6 ampere to split the remainder of the sample into paramagnetic and nonmagnetic fractions.
Rock samples were crushed and then pulverized to minus 0.15 mm with ceramic plates.
Sample Analysis
Spectrographic nethod
The stream-sediment, heavy-mineral-concentrate, rock samples and soil samples were analyzed for 31 elements using a semiquantitative, direct-current arc emission spectrographic method (Grimes and Marranzino, 1968). The elements analyzed and their lower limits of determination are listed in table 1. Spectrographic results were obtained by visual comparison of spectra derived from the sample against spectra obtained from standards made from pure oxides and carbonates. Standard concentrations are geometrically spaced over any given order of magnitude of concentration as follows: 100, 50, 20, 10, and so forth. Samples whose concentrations are estimated to fall between those values are assigned values of 70, 30, 15, and so forth. The precision of the analytical method is approximately plus or minus one reporting interval at the 83 percent confidence level and plus or minus two reporting intervals at the 96 percent confidence level (Motooka and Grimes, 1976). Values determined for the major elements (iron, magnesium, calcium, and titanium) are given in weight percent; all others are given in parts per million (micrograms/gram).
Chemical methods
Other methods of analysis used on samples from the Whipple Mountains Wilderness Study Area are summarized in table 2.
Analytical results for stream-sediment, heavy-mineral-concentrate, and rock and soil samples are listed in tables (3, 4, and 5, respectively).
ROCK ANALYSIS STORAGE SYSTEM
Upon completion of all analytical work, the analytical results were entered into a computer-based file called Rock Analysis Storage System (RASS). This data base contains both descriptive geological information and analytical data. Any or all of this information may be retrieved and converted to a binary form (STATPAC) for computerized statistical analysis or publication (VanTrump and Miesch, 1977).
DESCRIPTION OF DATA TABLES
Tables 3-5 list the results of analyses for the samples of stream sediment, heavy-mineral concentrate, rock and soils, respectively. For the three tables, the data are arranged so that column 1 contains the USGS- assigned sample numbers. These numbers correspond to the numbers shown on the site location maps (plate 1). Columns in which the element headings show the letter "s" below the element symbol are emission spectrographic analyses; "cm" indicates colorimetric; "instr" indicates Jerome gold-film mercury detector; and "aa" indicates atomic absorption analyses. A letter "N" in the tables indicates that a given element was looked for but not detected at the lower limit of determination shown for that element in table 1. If an element was observed but was below the lowest reporting value, a "less than" symbol (<) was entered in the tables in front of the lower limit of determination. If an element was observed but was above the highest reporting value, a "greater than" symbol (>) was entered in the tables in front of the upper limit of determination. If an element was not looked for in a sample, two dashes ( ) are entered in tables 3-5 in place of an analytical value. Because of the formatting used in the computer program that produced tables 3-5, some of the elements listed in these tables (Fe, Mg, Ca, Ti, Ag, and Be) carry one or more nonsignificant digits to the right of the significant digits. The analysts did not determine these elements to the accuracy suggested by the extra zeros.
REFERENCES CITED
Anderson, J. L., and Frost, E. G., 1981, Petrologic, geochronologic, and structural evaluation of the allochthonous crystalline terrane in the Copper Basin area, Eastern Whipple Mountains, southeastern California: February 1981, unpublished report, 63 p.
Anderson, J. L., 1981, Conditions of mylonitization in a Cordilleranmetamorphic complex, Whipple Mountains, California, Ein R. Techtonic framework of the Mojave and Sonoran Deserts, California and Arizona: U.S. Geological Survey Open-File Report 81-503, p. 1-3.
Anderson, J. L., and Rowley, M. C., 1981, Synkinematic intrusion of two-mica and associated metaluminous granitoids, Whipple Mountains, California: Canadian Mineralogist, v. 19, p. 83-101.
Anderson, J. L., Davis, F. A., and Frost, E. G., 1979, Field guide to regional Miocene detachment faulting and early Tertiary(?) mylonitization, Whipple-Buckskin-Rawhide Mountains, southeastern California and western Arizona, in Geologic Excursions in the southern California area, Abbott, P. L., ed., San Diego State University, San Diego, California.
Carr, W. J., 1981, Tectonic history of the Vidal-Parker region, California and Arizona, in Tectonic framework of the Mojave and Sonoran Deserts, California and Arizona: U.S. Geological Survey Open-File Report 81-503, p. 18-20.
Carr, W. J., Dickey, D. D., and Quinlivan, W. D., 1980, Geologic map of the vidal NW, Vidal Junction, and parts of the Savahia Peak SW and Savahia Peak quadrangles, San Bernardino County, California: U.S. Geological Survey Miscellaneous Investigations Map 1-1126.
Davis, G. A., Anderson, J. L., Frost, E. G., and Shackelford, T. J., 1980, Mylonitization and detachment faulting in the Whipple-Buckskin-Rawhide Mountains terrain, southeastern California and western Arizona, i^ Crittenden, M. D., Davis, G. A., and Coney, P. J., eds., 1980, cordilleran metamorphic core complexes, Geological Society of America Memoir 153, p. 79-129.
Davis, G. A., Anderson, J. L., Martin, D. L., Krummenacher, D., Frost, E. G., and Armstrong, R. L., 1982a, Geologic and geochrono"logic relations in the lower plate of the whipple detachment fault, Whipple Mountains, southeastern California: A progress report, jn Frost, E. G., and Martin, D. L., eds., 1982, Mesozoic-Cenozoic Tectonic Evolution of the Colorado River Region, California, Arizona, and Nevada (Anderson-Hamilton Volume): San Diego, Cordilleran Publishers, p. 408-432.
Dickey, D. D., Carr, W. J., and Bull, W. B., 1980, Geologic map of the Parker NW, Parker and parts of the Whipple Mountains SW and Whipple Wash quadrangles, California and Arizona: U.S. Geological Survey Miscellaneous Investigations Map 1-1124.
Frost, E. G., 1980, Appraisal design data, structural geology and water- holding capability of rocks in the Whipple Wash area, San Bernardino County, California: Unpublished report for United States Water and Power Resources Service Lower Colorado Regional Office, Boulder City, Nevada, June 1980, P.O. 0-01-30-07110, 88 p.
Grimes, D. J., and Marranzino, A. P., 1968, Direct-current arc andalternating-current spark emission spectrographic field methods for the semiquantitative analysis of geologic materials: U.S. Geological Survey Circular 591, 6 p.
Motooka, J. M., and Grimes, D. J., 1976, Analytical precision of one-sixth order semiquantitative spectrographic analyses: U.S. Geological Survey Circular 738, 25 p.
Thompson, C. E., Nakagawa, H. M., and Van Sickle, G. H., 1968, Rapid analysis for gold in geologic materials, rn Geological Survey research 1968: U.S. Geological Survey Professional Paper 600-B, p. B130-B132.
VanTrump, George, Jr., and Miesch, A. T., 1977, The U.S. Geological Survey RASS-STATPAC system for management and statistical reduction of geochemical data: Computers and Geosciences, v. 3, p. 475-488.
Vaughn, W. W., and McCarthy, J. H., Jr., 1964, An instrumental technique for the determination of submicrogram concentrations of mercury in soils, rocks, and gas, jn Geological Survey research 1964: U.S. Geological Survey Professional Paper 501-D, p. D123-D127.
Ward, F. N., Lakin, H. W., Canney,, F. C., and others, 1963, Analyticalmethods used in geochemical exploration by the U.S. Geological Survey: U.S. Geological Survey Bulletin 1152, 100 p.
Welsch, E. P., and Chao, T. T., 1975, Determination of trace amounts of antimony in geologic materials by atomic absorption spectrometry: Analytica Chimica Acta, v. 76, p. 65-69.
Welsch, E. P., 1983, Spectrophotometrical determination of tungsten in geological materials by complexing with dithiol: Talanta, v. 30, p. 876-878.
TABLE 1. Limits of determination for the spectrographic analysis of rocks andstream sediments, based on a 10-ng sample
[The spectrographic limits of determination for heavy-mineral-concentrate samples are based on a 5-mg sample, and are therefore two reporting intervals higher than the limits given for rocks and stream sediments]
Elements Lower determination limit Upper determination limit
