Geology topics
J. M. Nishi
Publications and source records attributed to J. M. Nishi.
The concentration and mobility of elements in subalpine forest soils in Colorado and Idaho
Leaching studies of subalpine forest soils collected at seven sites in Colorado and Idaho show that copper, cobalt, chromium, magnesium, barium, tin, strontium, and yttrium are highly mobile elements in these soils; that zirconium, lanthanum, nickel, and scandium are moderately mobile; and that titanium is rather immobile. Furthermore, the results of the studies indicate that elements are most highly concentrated in the ash of the mull (02) horizon. In these soils, the mull horizon is a more favorable zone for the accumulation of metals and other elements than are the mineral (A,B,C) soil horizons.
Anomaly patterns for selected metals in heavy mineral concentrates and oxalic acid residues, Dwyer Quadrangle, Grant and Luna counties, New Mexico
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Map showing anomalous lead distribution in stream sediment concentrates, Hillsboro and San Lorenzo quadrangles, exclusive of the Black Range Primitive Area, Sierra and Grant counties, New Mexico
This map shows the distribution of anomalous lead in the two sample fractions, magnetic (M-1) and nonmagnetic (NM-1) plotted on a base which includes sample localities, topography, and generalized geology modified from Hedlund (1975a, b). It is part of a series of maps for several metals that accompany this folio. Distributions of the lead values are shown on the accompanying histograms.
A statistical summary and listing of the spectrographic analyses of heavy mineral concentrate and conventional, sieved stream-sediment samples, Silver City area, New Mexico
Geochemical sampling of a tier of eight 7 1/2-minute quadrangles bordered by latitudes 32° 45'and 33° 00' N. and longitudes 108° 00' and 108° 30' W. was begun in the fall of 1974 and continued seasonally until completion in the fall of 1976. These quadrangles are in southwest New Mexico and include the well-known mineral deposits of the Silver City area. The sampling was designed to gain semidetailed information on the metal-anomaly characteristics of the strongly mineralized area surrounding Silver City, New Mexico, and to seek geochemical clues for the continuation of these mineral deposits beneath overlying Tertiary volcanic rocks to the north. The data obtained within areas of known mineral deposits provide information on the metallogenic processes and metal suites that both relate and distinguish metal systems. Evaluation of this information relative to the regional geologic framework and the distribution of known mineral deposits will result in the identification of additional target areas for exploration, as well as further our understanding of the geochemical characteristics of mineralized areas. Extrapolation of models developed from the study of areas of known, exposed mineralization to areas covered by Tertiary volcanic rocks, such as the northern part of this tier of quadrangles, is a promising procedure for continuing research into geochemical-anomaly characteristics of covered mineral deposits. Preliminary interpretation of the data indicates that the southern part of the area in which Paleozoic-Mesozoic rocks and mineral deposits are exposed, should be reassessed to the classification and genesis of some of the deposits and to the types of mineral commodities that may be present. Some wholly new exploration targets within these areas are also indicated by some of the data. In addition, geochemical clues to buried mineral deposits, possibly representing continuation northward of some features of the Silver City mining district, have been observed in data from the northern, Tertiary volcanic areas. The meanings of these clues are still speculative. For this study, 917 stream-sediment and 921 stream-sediment concentrate samples were collected. The stream-sediment-concentrate samples, which consist of heavy minerals, were split into magnetic and nonmagnetic fractions, each of which was analyzed. This resulted in the analysis of 1,842 heavy-mineral and 917 sieved stream-sediment samples. Analytical results for all of the sample types are summarized statistically on table 1 and tabulated in their entirety on table 2.
Spectrochemical determination of trace elements in galena
A semiquantitative spectrochemical method is described by means of which 10-mg samples of galena can be analyzed for their trace element content. Results on 40 elements are reported as six logarithmically spaced intervals per order of magnitude and obtained by visual comparison with standards prepared in spectrographically pure lead sulfide. Detection limits are generally between 1 and 20 ppm (except for Ce, Na, Sr, Ta, and Zn, which are 50 to 100 ppm). Replicate analyses of galena samples indicate a precision comparable to other semiquantitative spectrochemical methods used for the analysis of geochemical samples. Results obtained from the analysis of 129 galena samples are summarized.