Organic carbon, age, lithology, and CPI-alkenes at DSDP Sites 57-440 and 56-436

"Bound" and "free" solvent-extractable lipids have been examined from Sections 440A-7-6, 440B-3-5, 440B-8-4, 440B-68-2, and 436-11-4. The compound classes studied include aliphatic and aromatic hydrocarbons, ketones, alcohols, and carboxylic acids. Carotenoids and humic acids have also been examined. The quantitative results are considered in terms of input indicators, diagenesis parameters, and structural classes. A difference in input is deduced across the Japan Trench, with a higher proportion of autochthonous components on the western inner trench slope compared with the more easterly, outer trench, wall and greater input in the early Pleistocene than in the Miocene. A variety of diagenetic transformations is observed at Site 440 as sample depth increases. Results are compared with those of samples from Atlantic Cretaceous sediments and from the Walvis Bay high productivity area.

Geochemistry of rocks from Palmer Archipel

During the antarctic summer season in 1984 and 1986 field studies and laboratory investigations of the Mesozoic Intrusive Suite of the Palmer Archipel were carried out in cooperation with the Chilean Antarctic Institute and the University of Concepcion, Volcanic formations and intrusive series are the dominant exposed rocks together with very subordinate metasediments. Different petrological and isotopic data allow to divide the Antarctic Intrusive Suite into two intrusive types: a) Palmer Batholith (Lower Cenozoic) b) Costa Danco intrusive rocks (Upper Cretaceous). Both types belong to a calc-alkaline series. The granitoid rocks show an I-type-affinity. Ore minerals (pyrite, chalcopyrite, bornite, covellite, cuprite, pyrrhotite, magnetite and ilmenite) are mainly restricted to the intermediate rock types (e. g. granodiorites}. Propylitisation and kaolinisation are the observed alteration types, which suggest, together with the disseminated and vein-like ore fabrics the comparison with the andean Porphyry-Copper- and vein-type-deposits. The volcanic formations are subdivided into a) the Upper Cretaceous Wiencke Formation, which is composed of andesites and andesitic breccias, and b) into the Jurassic Lautaro Formation with basaltic, andesitic, dacitic and some rhyolitic rocks together with volcanic breccias. These calc-alkaline volcanic rocks apparently are part of an island are. A strong alteration of primary minerals is very common; however, the low ore mineral content does not change significantly within the different alteration types.

C1-C7 volatile organic compounds in sediments at DSDP Legs 56-57 Holes

Volatile C1-C7 components in sediments were examined for Japan Trench DSDP Sites 438, 439, 435, 440, 434 and 436, proceeding from west to east. Levels of all components are lowest in the highly fractured sediments of Sites 440 and 434. A number of alkenes, furans, and sulfur compounds were detected in concentrations higher than noted in any other DSDP sediments examined to date. The types, amounts, and specificity of occurrence are similar to those for 1-meter gravity cores we have examined which bear a significant biological imprint. Site 436 shows high levels of saturated and aromatic hydrocarbons, as well as olefins, including traces of dimethycyclopentanes and the highest level of cyclohexene detected in any DSDP sediment we have examined to date. The results from Site 436 were unexpected, considering the low organic-carbon content, absence of biogenic methane, and evidence of an aerobic depositional environment at this site.

Chemical and isotope composition of rocks from the Omgon Range, Western Kamchatka coastal area

Hypabyssal rocks of the Omgon Range, Western Kamchatka that intrude Upper Albian-Lower Campanian deposits of the Eurasian continental margin belong to three coeval (62.5-63.0 Ma) associations: (1) ilmenite gabbro-dolerites, (2) titanomagnetite gabbro-dolerites and quartz microdiorites, and (3) porphyritic biotite granites and granite-aplites. Early Paleocene age of ilmenite gabbro-dolerites and biotite granites was confirmed by zircon and apatite fission-track dating. Ilmenite and titanomagnetite gabbro-dolerites were produced by multilevel fractional crystallization of basaltic melts with, respectively, moderate and high Fe-Ti contents and contamination of these melts with rhyolitic melts of different compositions. Moderate- and high-Fe-Ti basaltic melts were derived from mantle spinel peridotite variably depleted and metasomatized by slab-derived fluid prior to melting. The melts were generated at variable depths and different degrees of melting. Biotite granites and granite aplites were produced by combined fractional crystallization of a crustal rhyolitic melt and its contamination with terrigenous rocks of the Omgon Group. The rhyolitic melts were likely derived from metabasaltic rocks of suprasubduction nature. Early Paleocene hypabyssal rocks of the Omgon Range were demonstrated to have been formed in an extensional environment, which dominated in the margin of the Eurasian continent from Late Cretaceous throughout Early Paleocene. Extension in the Western Kamchatka segment preceded the origin of the Western Koryakian-Kamchatka (Kinkil') continental-margin volcanic belt in Eocene time. This research was conducted based on original geological, mineralogical, geochemical, and isotopic (Rb-Sr) data obtained by the authors.

Geochemistry at DSDP Legs 56-57 Holes

About 200 volcanic ash layers were recovered during DSDP Leg 57. The volcanic glass in some of these layers was investigated petrographically and chemically in this study. Volcanic glass is mainly rhyolitic and/or rhyodacitic in chemical composition, and its refractive index ranges from 1.496 to 1.529. Some volcanic ash layers consist of multiple grains of different chemical compositions. All the volcanic glass belongs to the tholeiitic and the calc-alkalic volcanic rock series, in SiO2-(Na2O + K2O) diagram and FeO*/MgO-SiO2 diagram. We correlated successfully three volcanic ash layers from the standpoint of chemical composition and biostratigraphy. Hydration of volcanic glass from Leg 57 is less intense than in other DSDP cores.