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A new set of age data on some granitic batholiths of southeast China is reported. It is shown that these new data support the postulate of Larsen and Putman (1972) that, during the late Mesozoic, the Pacific sea floor was spreading from at least five spreading centers joined at two triple points. Attention is called to the coeval occurrence of paired metamorphism and intrusion on both sides of the Pacific during the Mesozoic.
Results are presented of three early applications of imagery from the NASA Earth Resources Technology Satellite to geologic studies in California. In the Coast Ranges near Monterey Bay, numerous linear drainage features possibly indicating unmapped fracture zones were mapped within one week after launch of the satellite. A similar study of the Sierra Nevada near Lake Tahoe revealed many drainage features probably formed along unmapped joint or faults in granitic rocks. The third study, in the Peninsular Ranges, confirmed existence of several major faults not shown on published maps. One of these, in the Sawtooth Range, crosses in Elsinore fault without lateral offset; associated Mid-Cretaceous structures have also been traced continuously across the fault without offset. It therefore appears that displacement along the Elsinore fault has been primarily of a dip-slip nature, at least in this area, despite evidence for lateral displacement elsewhere.
Extensive geological and geophysical surveys were carried out at the Marysville geothermal area during 1973 and 1974. The area has high heat flow (up to microcalories per square centimeter-second, a negative gravity anomaly, high electrical resistivity, low seismic ground noise, and nearby microseismic activity. Significant magnetic and infrared anomalies are not associated with the geothermal area. The geothermal anomaly occupies the axial portion of a dome in Precambrian sedimentary rocks intruded by Cretaceous and Cenozoic granitic rocks. The results from a 2.4-km-deep test well indicate that the cause of the geothermal anomaly is hydrothermal convection in a Cenozoic intrusive. A maximum temperature of 95 C was measured at a depth of 500 m in the test well.
Boulder 1 from Station 2 at the foot of South Massif is unique in being the only stratified boulder sampled by the Apollo 17 astronauts. Our studies of two of the four specimens that were collected from separate layers show that the boulder is composed of glass-poor, fragment-rich breccias which are aggregates of differentially annealed terra material, mainly ANT, but including basaltic troctolite, pigeonite basalt, granitic particles, dark breccia-rimmed anorthositic clasts, and a KREEPless norite that has not been recognized elsewhere at the Apollo 17 site. The boulder appears to derive from the uppermost blue-gray layer on South Massif, which we believe consists of ejecta deposited from a single large impact event (possibly the one which excavated the Serenitatis Basin).
We report the concentrations of Th, K, Fe, Mg, and Ti in 28 geographic regions overflown by the Apollo 15 and 16 spacecraft, as determined by gamma-ray spectrometry. The observed chemical compositions are consistent with ground truth, and the two missions give reasonable agreement in a region observed by both. The chemical compositions observed require a more complex model for interpretation than the previously reported radioactivity maps. Both highlands and maria show significant variations in composition. The van de Graaff region is unique; it may possibly be the source region for 'granitic' materials such as rock 12013.
The K-U, Th-U, and Th-Al systematics for lunar samples from the Apollo 11-17 missions and the Luna 16 and 20 missions are summarized. With few exceptions (granitic portion of 12013 and the Apollo 17 mare basalts) the Th/U ratio is 3.8 plus or minus 0.2. The K/U ratio for lunar samples is about 2600 and is distinctly different from the K/U ratio found in terrestrial samples and in the majority of meteorites. The K-U systematics are similar to the K-La, K-Sm, K-Ba, and K-Zr systematics, suggesting that the moon accreted approximately homogeneously. Based on a model the moon contains an average abundance of about 80 ppb U, about 200 ppm K, and about 7 times chondritic abundances for all the refractory elements such as Al, Ca, Ti, Zr, Ba, Sr, and REE. The Th-Al systematics of many lunar highland rocks are dominated by the presence of the rock-type KREEP.
Geological analysis of LANDSAT-1 Scene MSS 1053-17540 suggests that certain known mineral districts in east-central Nevada frequently occur near faults or at faults or lineament intersections and areas of complex deformation and flexures. Seventeen (17) areas of analogous characteristics were identified as favorable targets for mineral exploration. During reconnaissance field trips eleven areas were visited. In three areas evidence was found of mining and/or prospecting not known before the field trips. In four areas favorable structural and alteration features were observed which call for more detailed field studies. In one of the four areas limonitic iron oxide samples were found in the regolith of a brecciated dolomite ridge. This area contains quartz veins, granitic and volcanic rocks and lies near the intersection of two linear fault structures identified in the LANDSAT-1 imagery. Semiquantitative spectroscopic analysis of selected portions of the samples showed abnormal contents of arsenic, molybdenum, copper, lead, zinc, and silver. These limonitic samples found were not in situ and further field studies are required to assess their source and significance.
The author has identified the following significant results. Late autumn imagery provides the advantages of topographic shadow enhancement and low cloud cover. Mapping of rock units was done locally with good results for alluvium, basin fill, volcanics, inclined Paleozoic and Mesozoic beds, and host strata of bentonite beds. Folds, intrusive domes, and even dip directions were mapped where differential erosion was significant. However, mapping was not possible for belt strata, was difficult for granite, and was hindered by conifers compared to grass cover. Expansion of local mapping required geologic control and encountered significant areas unmappable from ERTS imagery. Annotation of lineaments provided much new geologic data. By extrapolating test site comparisons, it is inferred that 27 percent of some 1200 lineaments mapped from western Montana represent unknown faults. The remainder appear to be localized mainly by undiscovered faults and sets of minor faults or joints.
Large plateaus of Eocene limestone and exposed limestone escarpments, in Egypt and Saudi Arabia, respectively, were indicated by cool brightness temperatures recorded by the Nimbus-5 electrically scanning microwave radiometer (ESMR), over a 2-year period. Nubian sandstone, desert eolian sand, and igneous-metamorphic rock of the Pliocene, Miocene, Oligocene, and Cretaceous periods were differentiated from these limestone areas by warm T sub B values. These brightness temperature differences are a result of seasonal in-situ ground temperatures and differential emissivity of limestone and sand, sandstone and granite, whose dielectric constants are 6 to 8.9 and 2.9 and 4.2 to 5.3, respectively, at 19.35 GHz.
The major-element compositions of 93 low-specific-gravity (less than 2.60) high-silica (greater than 60%) glass particles from a sample of lunar fines (14259,20) were determined by electron microprobe analyses. The size, shape, abundance, mineralogy, and major-element composition of more than 60% of the high-silica glasses is consistent with their being fragments of interstitial glass from mare basalts. However, one group of 30 glasses with between 72% and 78% SiO2 and an average of approximately 2.6% FeO can be distinguished from other high-silica glasses both chemically and petrographically. Glass particles with this composition do not contain crystalline inclusions and are fairly homogeneous not only within a single particle but also from particle to particle. The chemistry and petrology of these glasses suggest that they are not fragments of interstitial glass or shock-melted particles from a 'granitic' source rock. Rather, the homogeneity and lack of crystalline inclusions suggest that this group of high-silica glasses was the product of lunar acidic volcanism.
The importance of hypervelocity impacts as a geologic process is demonstrated by the example of the Bushveld Complex and the (nearby) Vredefort Ring. Each is interpreted as the result of four simultaneous impacts modified by large-scale endogenic processes triggered by the impact event. The layered mafic sequence and the voluminous red granite associated with the complex are endogenic magmas, probably generated by pressure release accompanying crater excavation. Shock melting of older sedimentary rocks must have produced a layer of impact melt (the Rooiberg Felsite), the upper part of which was extruded over its originally chilled crust as a series of thick lava flows. Field evidence and radiometric age determinations indicate that the Bushveld Complex formed approximately 2000 billion years ago.
Results are reported for analysis of the uranium in multiple samples of each of six igneous-rock standards (dunite, granite, lujavrite, norite, pyroxenite, and syenite) prepared as geochemical reference standards for elemental and isotopic compositions. Powdered rock samples were examined by measuring delayed neutron emission after irradiation with a flux of the order of 10 to the 13th power neutrons/sq cm per sec in a nuclear reactor. The measurements are shown to compare quite favorably with previous uranium determinations for other standard rock samples.
Wafer-like crystals suitable for making solar cells are formed by pouring molten Si containing suitable dopants into a mold of the desired shape and allowing it to solidify in a temperature gradient, whereby the large surface of the melt in contact with the mold is kept at less than 200 D and the free surface is kept at a temperature of 200-1000 D higher, but below the melting point of Si. The mold can also be made in the form of a slit, whereby the 2 sides of the mold are kept at different temperatures. A mold was milled in the surface of a cylindrical graphite block 200 mm in diameter. The granite block was induction heated and the bottom of the mold was cooled by means of a water-cooled Cu plate, so that the surface of the mold in contact with one of the largest surfaces of the melt was held at approximately 800 D. The free surface of the melt was subjected to thermal radiation from a graphite plate located 2 mm from the surface and heated to 1500 D. The Si crystal formed after slow cooling to room temperature had a columnar structure and was cut with a diamond saw into wafers approximately 500 mm thick. Solar cells prepared from these wafers had efficiencies of 10 to 11%.
Digital LANDSAT MSS data for an area in the southwestern Arabian Shield were computer-enhanced to improve discrimination of rock classes, and recognition of gossans associated with massive sulphide deposits. The test area is underlain by metamorphic rocks that are locally intruded by granites; these are partly overlain by sandstones. The test area further includes the Wadi Wassat and Wadi Qatan massive sulphide deposits, which are commonly capped by gossans of ferric oxides, silica, and carbonates. Color patterns and boundaries on contrast-stretched ratio color composite imagery, and on complementary images constructed using principal component and canonical analyses transformations, correspond exceptionally well to 1:100,000 scale field maps. A qualitative visual comparison of information content showed that the ratio enhancement provided the best overall image for identification of rock type and alteration products.
Optical examination of nine polished grain mounts of Luna-24 drill-core material (0.09-0.50 mm size) revealed melt inclusions in olivine crystals. Two inclusions consist of clear glass with exceptionally high Si, yet contain no visible daughter minerals and have had no reaction effects with the olivine walls. Their compositions (one has SiO2 93.8, Al2O3 1.51, FeO 2.32, MgO 1.61, CaO 0.06, Na2O less than 0.05, K2O 0.11, total 99.41%; the other is similar) are unique and quite unlike the high-Si high-K melt of granitic composition that is found as inclusions in late-stage minerals of these (and the Apollo) samples, from silicate liquid immiscibility. The host olivines are Fo73 and Fo51. The origin of the melt in the inclusions and the lack of reaction effects are perplexing unsolved problems.
Linear strain of a rock sample as a function of hydrostatic pressure can be measured with a precision of 2 millionths. Such high-precision data for three orthogonal directions allow calculation of the distribution function for the porosity due to cracks' closing completely at a given pressure. Such data for at least six independent directions yield the zero-pressure strain tensor due to cracks' closing completely at a given pressure. The principal values and axes of this tensor distribution function provide information about the orientation of cracks as a function of closure pressure. The mathematical basis for the technique is developed, and the technique is illustrated with differential strain data for two samples, the Westerly (Rhode Island) granite and the Twin Sisters (Washington) dunite. Strain-tensor calculations reveal that each of these samples has a different type of anisotropic crack distribution.
The basement rocks of Manicouagan exhibit a wide compositional range (40-72% SiO2). Least squares mixing calculations indicate that the average composition of the Manicouagan melt sheet can be modeled for 9 major and 11 trace elements by a mixture of 4.5% anorthosite, 55.5% mafic gneiss, and 40.0% tan gneiss with a granitic-granodioritic composition. The underrepresentation of anorthosite relative to its present distribution is considered. The homogeneous composition of the melt (57.75 + or - 1.21% SiO2) relative to that of the postulated target is explained in a model outlining the dynamic conditions existing during the formation of the melt and its accompanying movement into the excavated cavity.
The lunar sample 12013, a complex mixture of gray breccia and black breccia, is described. The gray breccia consists of mostly basaltic and gabbroic lithic clasts as well as plagioclase and pyroxene mineral clasts set in a matrix of smaller clasts and a felsite of granitic composition, while the black breccia is comprised of mostly mineral clasts, some lithic clasts, and felsite blebs enclosed in an aphanitic groundmass of basaltic composition. Textural relationships indicate that the felsite and the black breccia groundmass crystallized from melts which coexisted prior to the final lithification of 12013 but failed to mix. Both the felsite and the black breccia groundmass have extreme enrichments of incompatible elements. The critical feature of their compositions is a 'splitting up' of incompatible element associations so that the highest REE and P concentrations are in the black breccia groundmass, and the highest K, Ba, and Rb concentrations are in the felsite.