Outcrop samples

Petrographic observations were made on polished thin sections, for 313 outcrop samples. Average sample spacing was one sample per 1 km within a radius of 15 km or less from the known porphyry Cu-Mo deposits, and one sample per 2 km outside this area. Five rock types are distinguished in the district andesites, diorites, granodiorites, dacites, rhyolites and sandstones. Rhyolites and dacites dominate in the zone of known porphyry Cu-Mo deposits. Sandstones are much less common and were not studied. 

Lithogeochemistry was initially applied to the rocks from the Sherridon complex in an attempt to help clarify the stratigraphy of the volcanic sequence. To date, the major- and trace-element compositions of 1964 samples of drill core and 751 outcrop samples have been analysed by... 

Two general areao in Colorado exhibit extensive alteration of coalo by igneouo intrusives. The first locality it near Somerset in the west central part of the state, and the second area is the Spanish Peaks region near Trinidad and Walsenburg. Drill core samples, outcrop samples, materials from active mines, and thin sections of the intrusive rocks were studied. The results show that mean maximum reflectance of the altered coal or natural coke increases as the distance from an intrusive body decreases. Carbon and ash values increase as the distance from intrusive decreases whereas volatile matter values decrease. Sulfur data are variable. Hydrogen values increase as the distance from an intrusive increases. Hydrogen and reflectance are considered the most sensitive and reliable indicators of degree of alteration. 

The Battle Creek, Wyoming outcrop sample has substantial amounts of vanadyl porphyrins, indicating that petroporphyrins may be preserved even after prolonged exposure to weathering agents. 

Table II shows the results obtained by extracting several Uinta Basin, Utah outcrops with successive organic solvents. All outcrop samples are fairly low in sulfur, most are quite high in nitrogen, and all have low ratios of vanadium to nickel. Only the Raven Ridge sample, which was collected in a creek bed, has a very large fraction of organic material that is not soluble in heptane Benzene-methanol (1 1) and pyridine did not extract much material from any of these samples, so analytical data from these materials are not included in the table. The asphaltenes extracted from P. R. Spring and Southeast Asphalt Ridge tar sands are quite rich in nickel (5/jtmol/g), and nickel porphyrins are found in the heptane-soluble fractions of these tar sands as well as is the heptane-soluble fraction of Whiterocks tar sands. Crudes derived from nonmarine sources are usually much higher in nickel content than in vanadium content, and the Uinta Basin tar sands deposits are all of lacrustine origin and are of tertiary age.

Another type of variation, observed for outcrop samples in Labrador as well as in the eastern United States (9,JO), is shown in Figure 4. In this case, each separate outcrop located within several miles of the other... 

The matching of outcrop samples with debitage and other artifactual material is an ideal problem for computer-assisted pattern recognition techniques (8). The use of ARTHUR for the analysis of the soapstone from Labrador will be discussed in a future publication, but the important parameters for comparing soapstone are given in Table II. For this table, the samples from a given quarry were taken as one or two groups. The... 

Although our study is based upon outcrop samples, and consequently does not directly relate to groundwater or hydrocarbon production problems, the Zia Formation in the subsurface is an important local aquifer, and similar alluvial units form significant aquifers and hydrocarbon reservoirs elsewhere. Thus the cementation relationships observed in the Zia Formation are of more than local interest. Calcite cementation in the Zia Formation has adversely affected potential reservoir/aquifer quality in two main ways ... 

Figure 5. Distribution of particle-size parameter (average diameter of cross-sectional area) for geothite (a-FeOOH) in samples of Middle Kittanning coal. Key A, high wall sample O, middle sample , outcrop sample and P, original pyrite sample. See Table / for definition of class limits.

Ye et al. (1999) investigated outcrop samples of the Bluejacket Sandstone (Middle Peimsylvania) and correlated permeability anisotropy with the internal facies architecture meandering channel-fill facies shows strong permeability anisotropy compared with low anisotropy of braided channel-fill facies. 

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