[1] We report on ages derived from impact crater counts for exposed mare basalt units in the northern part of the lunar nearside hemisphere (Mare Frigoris), the eastern and northeastern part of the nearside hemisphere (Lacus Temporis, Joliot, Hubble, Goddard, Mare Marginis, and Mare Smythii), the central part of the nearside hemisphere (Palus Putredinis, Mare Vaporum, and Sinus Medii), and the ...

pillow lavas are locally conspicuous. A unit consisting of dark, thinly bedded sandstone and siltstone, lccally ranging to several hundred feet thick, is lowermost in the exposed section. The middle division consists of about 3,500 feet of mixed andesi.:e and basalt volcaniclastic rocks ~ lahar, tuff breccia, volcanic sandstone, and conglomeratic beds which rest on relatively thin, fossiliferou...

Sediment-covered basalt on the flanks of mid-ocean ridges constitutes most of Earth's oceanic crust, but the composition and metabolic function of its microbial ecosystem are largely unknown. By drilling into 3.5-million-year-old subseafloor basalt, we demonstrated the presence of methane- and sulfur-cycling microbes on the eastern flank of the Juan de Fuca Ridge. Depth horizons with functional...

Basement rocks in the 17,000-square-mile region of southern Oklahoma crop out in the Wichita and Arbuckle Mountains and have been studied in subsurface samples from 175 wells. The rocks are divided into two contrasting provinces, each completely different from the other in age and petrologic character. Each province has played a different role in guiding the stratigraphic and structural evoluti...

Samples of basalt were collected during the Rapid Response cruise to Loihi seamount from a breccia that was probably created by the July to August 1996 Loihi earthquake swarm, the largest swarm ever recorded from a Hawaiian volcano. Po–Pb dating of two fresh lava blocks from this breccia indicates that they were erupted during the first half of 1996, making this the first documented historical ...

A flinty, spherulitic dyke of peralkaiine trachyte in a Precambrian dyke-swarm consists mainly of albite and aegirine. Within this, euhedral crystals of narsarsukite, NadTi,Fe)Si401o(F), occur as short prisms elongate parallel to c. This distinguishes them from all previously described narsarsukites, which have tabular habits. Minor phases present include micas, apatite, quartz, pectolite, nord...

Crustal assimilation (e.g. Hildreth and Moorbath, 1988) and/or subduction erosion (e.g. Stern, 1991; Kay et al., 2005) are believed to control the geochemical variations along the northern portion of the Chilean Southern Volcanic Zone. In order to evaluate these hypotheses, we present a comprehensive geochemical data set (major and trace elements and O–Sr–Nd–Hf–Pb isotopes) from Holocene primar...

Petrography and physicomechanical properties of alkali granites, alkali quartz syenite, and nepheline syenite from Ambela, NW Pakistan, have been investigated. Whereas the alkali quartz syenite and most of the alkali granites are megaporphyritic, the nepheline syenite and some of the alkali granites are microporphyritic. Their phenocryst shape and size and abundance of groundmass are also diffe...

The results of our infrared reflectance studies of single and mixed alkali borate glasses are reviewed and discussed in the context of the network structure and the interactions between alkali cations and their sites in the glass. In particular, we focus on the strong influence of the alkali cation type, content, and alkali subsitution on the structure of the network building units. The dominan...

Introduction: In understanding the evolution of the Moon, a number of its fundamental magmatic characteristics must be explained in the context of other geophysical and geological observations. Volcanic activity subsequent to the formation of anorthositic crust was dominated by the eruption of mare basalt. (1) The main phase of mare volcanism began ~500 Myr after the crystallization of the anor...