The Isua greenstone belt (Fig. 1) contains the oldest known, relatively well preserved, metavolcanic and metasedimentary rocks on Earth. The rocks are all deformed and many were substantially altered by metasomatism, but both the deformation and metasomatism were heterogeneous. Transitional stages can be seen from relatively well preserved primary volcanic and sedimentary structures to schists ...

Osmium isotope compositions and concentrations of Re, platinum group elements (PGE), and Au were determined for host peridotites (serpentinites and harzburgites) and hydrothermally altered ultramafic wall rocks associated with Mother Lode-type hydrothermal gold-quartz vein mineralization in the Alleghany district, California. The host peridotites have Os isotope compositions and Re, PGE, and Au...

The role of the subducting lithospheric slab in the genesis of mantle-derived (primitive) magmas is investigated through a study of volcanic rocks formed in the tectonically strike-slip–dominated western Aleutian arc. Two types of chemically and petrologically distinctive primitive andesites have been found among the Miocene– late Pleistocene–age volcanic rocks in the western Aleutians. These a...

Two-dimensional measurement of radiation produced by natural irradiation of granitic rocks was performed by the use of an imaging plate, which is a storage film coated with photostimulated phosphor (BaFBr:Eu2+). Radiation images of small volume specimens, such as thin sections were obtained with the imaging plate. Irradiation images of granitic rocks are inhomogeneous and the intensity of photo...

Introduction The special issue of this journal (Nov. 2000) that was devoted to “Some Great Ideas for Geoscience Courses,” included nine ideas under the heading “Earth materials.” Six of those papers involved classification (Thomas and Thomas, 2000; Dowse, 2000; Reynolds and Semken, 2000; Harper, 2000; Christman, 2000; Niemitz, 2000). Classification of rocks and minerals is obviously a necessary...

ONE petrological approach to upper mant le studies is to determine which ultramafic rocks represent mantle material. Ultramafic rocks occur in a variety of field and petrographic associations : in recent reviews, Wyllie [1967b, 1968] outlined eleven petrographic associations, some with subdivisions. In this summary, it is convenient to consider these in four larger groups: (1) layered, stratifo...

The jumping spider Habronattus dossenus Griswold 1987 (Salticidae) communicates using seismic signals during courtship and can be found on rocks, sand and leaf litter. We examined the filtering properties of, and tested the efficacy of male courtship signals on, these natural substrates. These substrates have drastically different filtering properties at the distances at which the males court. ...

High power carbon dioxide lasers have successfully been used in drilling or cutting ngineering materials such as metals, polymers and ceramics over the years. Can a arbon dioxide laser be used to efficiently drill different rocks in a deep gas well? esearch sponsored by US Department of Energy has been carried out to answer this uestion. This paper will report the study results of using a super...

We performed a ground level geomagnetic survey of Greene County, Ohio in the fall of 1976. The geomagnetic map showed a positive magnetic anomaly running from the northwestern section to the southeastern section of the county while the remainder of the map was relatively undisturbed. We analyzed the localized anomaly of the southeastern section by the Peters methods and by fitting to the model ...

The Ok Tedi Complex hosts a world-class porphyry copper-gold deposit. Samples from the Ok Tedi Complex and the neighbouring Mount Ian Complex were analyzed for major and trace elements using XRF and HR-ICP-MS, and the isotopic composition of S in sulphides was analyzed by Elemental Analyzer. Major element geochemistry indicates that both complexes are alkaline and contain rocks ranging in compo...