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D. E. Lee

Publications and source records attributed to D. E. Lee.

7 recordsLinked to original sources
USGS2012

Two-mica granites of northeastern Nevada

The field settings are described and analytical data are presented for six two-mica granites from north-eastern Nevada. High δ 18 O and 87 Sr/ 86 Sr values indicate that all are S-type granites, derived from continental crust. The major element chemistry and accessory mineral contents of these rocks also are characteristic of S-type granites. Chemical, X ray, and other data are presented for the micas recovered from these granites. The muscovites are notably high in Fe 2 O 3 , FeO, and MgO. Except for one hydrobiotite, each of the biotites has an MgO content near 6.0 weight percent. Two different types of two-mica granites are recognized in the area of this study. One type is distinguished by the presence of many biotite euhedra within muscovite phenocrysts and by an unusual suite of accessory minerals completely devoid of opaque oxides. This type probably resulted from anatexis of late Precambrian argillites under conditions of relatively low oxygen fugacity, along a line that roughly coincides with the westward disappearance of continental basement. In the other textural type of two-mica granite the micas are equigranular and there is a greater variety of accessory minerals. The magmatic evolution of this type also appears to reflect the influence of late Precambrian argillites; there may be age differences between the two types of two-mica granites.

Journal of Geophysical Research Solid Earth↗
USGS1984

Modification of δ D values in eastern Nevada granitoid rocks spatially related to thrust faults

Stable isotope data have been determined for 13 Mesozoic and Tertiary plutons in eastern Nevada and nearby Utah. In the southern Snake Range of eastern Nevada, where relations are best exposed and have been most intensively studied, δ D, δ 18 O, and apparent K-Ar ages depend on proximity to the Snake Range decollement. Where stresses resulting from late movement on the decollement have caused cataclasis of Oligocene (37 Ma) granitoid rock, δ 18 O, δ D, and K-Ar age values as low as −2.5‰, −155‰, and 18 Ma, respectively, have been determined. Where there has been no cataclasis, δ 18 O values of Jurassic, Cretaceous, and Oligocene granitoid rocks are apparently unaffected, but both δ D values and K-Ar ages have been modified for distances of tens of meters below the decollement. Results similar to those in the southern Snake Range have been observed in other eastern Nevada granitoid rocks spatially related to regional thrust faults, as in the Kern Mountains, the Toana Range, and the northern Egan Range. In each of these areas cataclasis or deformation of granitoid rocks has resulted in lowered δ 18 O, δ D, and K-Ar age values. Where there has been no cataclasis or deformation, δ 18 O values are unaffected, but both δ D and K-Ar age values have been lowered by stresses resulting from postcrystallization movement along overlying thrust faults. Many of the plutons discussed have not been deeply eroded, and spatially related thrust faults crop out. Where thrust faults are not in evidence and the granitoid rocks give δ D values lower than about −130‰ along with spuriously low K-Ar age results, modification of the δ D and K-Ar age values may have been caused by stresses related to late movement along an overlying (now eroded) thrust fault.

Contributions to Mineralogy and Petrology↗
USGS1983

The granite problem as exposed in the southern Snake Range, Nevada

A geochemically and mineralogically diverse group of granitoids is present within an area of 900 km2 in the southern Snake Range of eastern Nevada. The granitoids exposed range in age from Jurassic through Cretaceous to Oligocene and include two calcic intrusions, two different types of two-mica granites, and aplites. The younger intrusions appear to have been emplaced at progressively more shallow depths. All of these granitoid types are represented elsewhere in the eastern Great Basin, but the southern Snake Range is distinguished by the grouping of all these types within a relatively small area. The Jurassic calcic pluton of the Snake Creek-Williams Canyon area displays large and systematic chemical and mineralogical zonation over a horizontal distance of five km. Although major element variations in the pluton compare closely with Daly's average andesite-dacite-rhyolite over an SiO2 range of 63 to 76 percent, trace element (Rb, Sr, Ba) variations show that the zonation is the result of in situ fractional crystallization, with the formation of relatively mafic cumulates on at least one wall of the magma chamber. Models of trace element and isotopic data indicate that relatively little assimilation took place at the level of crystallization. Nonetheless, an initial 87Sr/86Sr value of 0.7071 and ??18O values of 10.2 to 12.2 permil suggest a lower crustal magma that was contaminated by upper crustal clastic sedimentary rocks before crystallization. The involvement of mantle-derived magmas in its genesis is difficult to rule out. Two other Jurassic plutons show isotopic and chemical similarities to the Snake Creek-Williams Canyon pluton. Cretaceous granites from eastern Nevada that contain phenocrystic muscovite are strongly peraluminous, and have high initial Sr-isotope ratios and other features characteristic of S-type granitoids. They were probably derived from Proterozoic metasediments and granite gneisses that comprise the middle crust of this region. Another group of granitoids (including the Tertiary aplites) show chemical, mineralogic, and isotopic characteristics intermediate between the first two groups and may have been derived by contamination of magmas from the lower crust by the midcrustal metasediments. ?? 1983 Springer-Verlag.

Contributions to Mineralogy and Petrology↗
USGS1981

The distribution of uranium and thorium in granitic rocks of the basin and range province, Western United States

Some secondary uranium deposits are thought to have formed from uranium derived by the weathering of silicic igneous rocks such as granites, rhyolites, and tuffs. A regional geochemical survey was made to determine the distribution of uranium and thorium in granitic rocks of the Basin and Range province in order to evaluate the potential for secondary uranium occurrences in the area. The resulting geochemical maps of uranium, thorium, and the Th:U ratio may be useful in locating target areas for uranium exploration. The granites were sampled according to a five-level, nested, analysis-of-variance design, permitting estimates to be made of the variance due to differences between:(1) two-degree cells; (2) one-degree cells; (3) plutons; (4) samples; and (5) analyses. The cells are areas described in units of degrees of latitude and longitude. The results show that individual plutons tend to differ in uranium and thorium concentrations, but that each pluton tends to be relatively homogeneous. Only small amounts of variance occur at the two degree and the between-analyses levels. The three geochemical maps that were prepared are based on one-degree cell means. The reproducibility of the maps is U > Th ⪢ Th:U. These geochemical maps may be used in three methods of locating target areas for uranium exploration. The first method uses the concept that plutons containing the greatest amounts of uranium may supply the greatest amounts of uranium for the formation of secondary uranium occurrences. The second method is to examine areas with high thorium contents, because thorium and uranium are initially highly correlated but much uranium could be lost by weathering. The third method is to locate areas in which the plutons have particularly high Th:U ratios. Because uranium, but not thorium, is leached by chemical weathering, high Th:U ratios suggest a possible loss of uranium and possibly a greater potential for secondary uranium occurrences to be found in the area.

Arizona, California, Nevada, Utah↗
USGS1963

Glaucophane-bearing metamorphic rock types of the Cazadero area, California

A detailed field and laboratory study has been made of a well-exposed glaucophane schist sequence within the Jurassic and Cretaceous Franciscan Formation of northern California. Three types of glaucophane-bearing metamorphic rocks have been distinguished in and around the area of the detailed study. Each is characterized by distinctive textures and mineral assemblages that are interpreted to represent different grades of metamorphism within the glaucophane schist facies. From the combination of small- and large-scale mapping in the area described it is clear that coarsely schistose blocks, tens of feet in diameter, commonly rest directly upon and within less intensely metamorphosed terrain. In the Cazadero area these isolated blocks of coarsely crystalline rocks are concentrated in a band that is roughly concordant with some of the major faulting, and their metamorphic fabric shows no consistent relation to local or regional structures. It is tentatively suggested that these blocks have been transported upward tectonically and that they are not stratigraphically equivalent to the other types of glaucophane-bearing metamorphic rocks in the area. Chemical and petrographic evidence indicates that basalt and sediments have been converted to glaucophane-bearing rocks under conditions of metamorphism that were essentially isochemical, except for fugitive components and some minor elements.

California↗
USGSDate not supplied

Garnet types from the Cazadero area, California

This is the third in a series of papers on glaucophane schists from the Franciscan Formation near Cazadero, California. Previous papers describe three distinct types of glaucophane-bearing Franciscan metamorphic rocks near Cazadero. The purpose of this study is to investigate the garnets present in metamorphic types III (bedrock schists) and IV (tectonic blocks) as defined by Coleman & Lee (1963). Twenty-four garnet analyses are presented. Sixteen of these are from (aragonite-bearing) type III glaucophane schists, and eight are from type IV glaucophane schists. Type IV rocks include California eclogites. Type III rocks include metabasalt, metachert, metashale, meta-ironstone, and metacarbonate that were formed under high pressure and relatively low temperature. These rocks contain garnets that display a wide range of composition, but the dominant molecules represented are consistently almandine, spessartine, and grossular. Type IV rocks are mainly metabasalts that were probably formed under higher temperatures and pressures than type III rocks. There is a distinct difference between garnets from type III rocks and those from type IV (including eclogites); the lattercontain less spessartine and more pyrope, and the dominant molecules are almandine and grossular. The four analyses of garnets from California eclogites have an average pyrope content of about ten molecular per cent, and they extend the range of composition reported for eclogite garnets. Quantitative spectrographic determinations of minor elements are listed for each of the garnets described. The values determined for some of the minor elements have a wide range and a capricious distribution over a few feet of outcrop area. As a group, both the garnets from type III rocks and those from type IV are pyralspites with large contents (as much as 35 molecular per cent) of ugrandite. This unusual admixture of the pyralspite and ugrandite garnet series may have resulted in part from the conditions (high pressures and relatively low temperatures) under which the enclosing rocks were recrystallized.

California↗