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Geology topics

Michael Fleischer

Publications and source records attributed to Michael Fleischer.

At least 19 recordsLinked to original sources
USGS1969

Gold in minerals and the composition of native gold

Gold occurs in nature mainly as the metal and as various alloys. It forms complete series of solid solutions with silver, copper, nickel, palladium, and platinum. In association with the platinum metals, gold occurs as free gold as well as in solid solution. The native elements contain the most gold, followed by the sulfide minerals. Several gold tellurides are known, but no gold selenides have been reported, and only one sulfide, the telluride-sulfide mineral nagyagite, is known. The nonmetallic minerals carry the least gold, and the light-colored minerals generally contain less gold than the dark minerals. Some conclusions in the literature are conflicting in regard to the relation of fineness of native gold to its position laterally and vertically within a lode, the nature of the country rocks, and the location and size of nuggets in a streambed, as well as to the variation of fineness within an individual nugget.

Circular↗
USGS1965

Some aspects of the geochemistry of yttrium and the lanthanides

Recent data on the relative abundances of the lanthanides and yttrium in meteorites, basaltic rocks, granitic rocks and sedimentary rocks are reviewed. It is shown that the data are inadequate to substantiate or to disprove Taylor's derivation from these data of a 1:1 abundance ratio of basaltic to granitic rocks in the continental crust. Graphs are given to illustrate the variation of lanthanides in minerals with paragenesis. Both the paragenesis and the crystal chemistry of minerals affect the composition of the lanthanides.

Geochimica et Cosmochimica Acta↗
USGS1963

The abundance of scandium in volcanic rocks, a preliminary estimate

Using Rittman's classification to determine the clan, we suggest the following abundance figures: basalts (99), 38 p.p.m. Sc; andesites (72), 34 p.p.m. Sc; dacites (68), 21 p.p.m. Sc; rhyodacites (32), 14 p.p.m. Sc; quartz latites (14), 11 p.p.m; rhyolites (24), 5 p.p.m. The scandium was determined spectrographically on samples for which there were complete rock analyses. In addition we suggest that extrusive equivalents of peridotites should contain about 9 p.p.m. Sc; extrusive equivalents of perknites should contain about 30 p.p.m. Sc. We see no reason why these figures should not apply to the intrusive equivalents. We tentatively suggest a figure of 30 p.p.m. for Sc for the crust, using Poldervaart's suggested ratio of rock types.

Geochimica et Cosmochimica Acta↗
USGS1959

The geochemistry of rhenium, with special reference to its occurrence in molybdenite

Little has been added to our knowledge of the geochemistry of Re since the work of Noddack and Noddack in 1931, except that many determinations have been published of the Re content of molybdenite, the only present source. These determinations, 150 in all, have been assembled. The Re content of molybdenite ranges from none to 3,250 p.p.m. Re, and varies widely, even in samples from a single deposit. No generalizations are yet possible as to correlations of Re content with geological conditions of formation. Other possible sources of Re are considered briefly.

Economic Geology↗
USGS1955

Estimates of the abundances of some chemical elements and their reliability

During the past thirty years the development of improved methods of analysis, especially optical spectrography, x-ray spectrography, and colorimetric methods, has resulted in a wealth of new data on the abundances of many elements. Nevertheless, present estimates differ greatly in reliability; some, such as the estimate for bismuth, are based on very few actual determinations, whereas others, such as that for gallium, are based on analyses of many samples. This paper reviews the estimates of abundance for the elements bismuth, germanium, gallium, and yttrium, taken as examples to illustrate the wide variation in reliability. For gallium and yttrium, a study has been made of spectrographic analyses by four laboratories of more than 600 chemically analyzed rocks from many areas of the world. Comparison shows that these furnish valuable data on abundance, although attention must be directed to regional variation. The comparison also shows the need for continued interlaboratory standardization. The estimate for bismuth is based on so few determinations that no appraisal of its accuracy can be made. The estimate for germanium is based on very few determinations but is almost certainly of the right order of magnitude, though perhaps slightly too high. The estimates for gallium and yttrium, based on many determinations, are almost certainly of the right order of magnitude, though that for gallium may be slightly low and that for yttrium may be substantially low.

GSA Special Papers↗