High phosphorus and low iron-content groundwaters from the southern Nishinomya district (Miyamizu groundwater), Japan, were analyzed for rare earth element (REE) and some major element concentrations. The chondrite-normalized REE patterns of these groundwaters are characterized by strong heavy REE enrichments relative to light REE, and slight-to-moderate negative Ce anomalies. The magnitude of Ce anomaly increases with decreasing Fe and increasing NO₃^- contents and pH. Such correlations are explained by the redox changes with depth in the area. The heavy REE inclinations of the chondrite-normalized REE patterns correlate positively with Ca and Mg contents and negatively with Fe contents. Heavy REE enrichment is explained by successive water-rock interactions supplying REE to the water in which differential scavenging of light REE by particulate matters occurs. The high P characteristic is achieved by the decomposition of biogenic materials under oxidizing conditions. The low Fe concentration of these groundwaters is ascribed to precipitation of Fe-hydroxides and their subsequent filtration as groundwater flows through the aquifer. The low P and high Fe groundwaters are thought to originate from a deeper aquifer experiencing reducing conditions. The unique geochemical characteristics of the groundwaters of the study area may be closely related to a peculiar geological situation in which an organic-rich layer is seated at relatively shallow depths within an aquifer of relatively large permeability.

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Rb-Sr geochronometry has been used in several studies in an effort to date pseudotachylyte and therefore the fault hosting the pseudotachylyte and the tectonism that produced the faulting. The usual procedure has been the “thin-slab” technique, which in metamorphic rocks involves construction of an isochron using whole rock analyses of adjacent but compositionally different slices of rock, and is based on the assumption of isotopic equilibrium between the slices. In attempts to date pseudotachylyte, analyses have been obtained using a pseudotachylyte vein and the immediately adjacent host rock. Such studies commonly yield: 1) apparent ages with high errors owing to small a small range of Rb/Sr values or to “scatterchron” data; 2) host rocks not plotting on the same isochron or scatterchron defined by the pseudotachylyte; 3) apparent dates that are inconsistent with other estimates of the time of faulting; or 4) apparent ages that are not independently constrained. These studies commonly fail to record the type of pseudotachylyte vein utilized; injection veins are commonly larger and more obvious targets for collecting but are likely to yield geologically meaningless dates. A Rb-Sr geochronometric study of pseudotachylyte from the North Cascade Mountains, Washington, reveals: 1) an apparent age older than the likely age of the pseudotachylyte; 2) pseudotachylyte and host rock chemical and isotopic characteristics indicating that the pseudotachylyte was not the result of bulk melting of normal schist; and 3) metasomatism prior to pseudotachylyte formation likely affected both the protolith and what is now the host rock. In light of previous studies, the new data, and related information regarding fault-related metasomatism, three closed system models and one open system model for pseudotachylyte formation are proposed. These models make specific predictions regarding apparent whole rock-pseudotachylyte dates, microstructural features, and the relationship between the whole-rock pseudotachylyte date and the whole rock-biotite Rb-Sr dates in the same rock. The models suggests pseudotachylyte-host rock dating is unlikely to produce real ages of pseudotachylyte formation. Worse, because many pseudotachylytes apparently form during cooling and uplift, the technique will instead yield a seemingly reasonable but geologically meaningless date. Certain approaches to the problem, including a microstructural analysis coupled with a whole rock-biotite age on the same rock, may yield an actual age of pseudotachylyte formation, but the assumptions made heretofore about the behavior of the Rb-Sr system at the time of pseudotachylyte formation are questionable.

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The Shidao complex at the eastern extremity of the Sulu ultrahigh pressure (UHP) terrane is composed of oldest pyroxene syenite, quartz syenite and youngest granite intrusives of the K-rich shoshonitic series. U-Pb zircon dating yields nearly concordant ages of 225 ± 2, 211 ± 3 and 205 ± 5 Ma for pyroxene syenite, quartz syenite and granite, respectively. The ages closely postdate the 240 to 220 Ma UHP metamorphism and correspond to the rapid cooling and exhumation of UHP rocks. A close genetic relation may exist between the formation of the Shidao intrusives and the continental collision and UHP metamorphism. However, the K-rich Shidao intrusive rocks are different from common syn-collisional granites in association of K-rich and granitic magmatism. A breakoff model is postulated to explain the formation of the complex. The breakoff of the subducting slab caused the rapid exhumation of the UHP terrane. Mantle upwelling resulted in basaltic magmatism and formation of the K-rich complex. Formation of the Shidao complex marked the cessation of the UHP metamorphism and the oldest ages of 225 ± 2 Ma of the complex is the minimum timing for the UHP metamorphism.

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Dissolved yttrium and rare earth elements (YREEs) have been measured in the Antarctic Circumpolar Current Region, southwest of Australia. Their vertical features are fairly smooth, irrespective of the different water masses in the water column, suggesting that the biogeochemical processes including reversible scavenging reactions and sinking particulate matter are important control on their distribution. Comparison to the previous data at nearly the same latitude of ∼40°S in the Southern Ocean of the Atlantic sector (German et al., 1995) indicates that our concentrations are significantly depleted in the lighter REEs. The difference in their mean concentrations systematically decreases with increasing atomic number, i.e., 67% for La, 40% for Nd, 15% for Sm and less than 5% for the REEs heavier than Tb and Y. Gadolinium is an exception to this trend with a deficit that is anomalously high at ∼36% compared to those of its neighbors, Eu and Tb. Negative Gd-anomalies exceeding 30% are recorded for the subsurface waters, which contrast with positive Gd anomalies of up to ∼20% in the North Pacific Deep Water (Alibo and Nozaki, 1999). The relative deficit of 62% for Ce(IV), perhaps fortuitously, fits well between those of La and Nd, despite its vertical profile being different from those of strictly tri-valent YREE(III)s. These observations cannot be explained simply by the REE fractionation during scavenging of particulate matter and/or regional variation of scavenging intensity alone, and suggest that there must be a REE compositional difference in the external sources, e.g., from shallow water sediments and lithogenic materials sinking through the water column. The unique REE(III) patterns of the Circumpolar Deep Water (CDW) and the Antarctic Bottom Water (AABW) with a LREE depletion in the southeastern Indian Ocean appear to be originated from igneous rocks around the Indonesian Archipelago. This is in contrast to the REE(III) patterns of a LREE enrichment with a maximum at Nd-Sm, reflecting continental sedimentary rocks, in the CDW and AABW in the South Atlantic and the western Indian Ocean. The markedly different REE patterns in the eastern and western components of CDW and AABW indicate that they can serve as novel tracers in elucidating the deep water circulation of the Indian Ocean.

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The mantle lithosphere beneath the North China Block (NCB) was significantly thinned during the last 400 million years. Comparative studies of early Paleozoic and Cenozoic lithospheric mantle have shown that the lost lithospheric mantle should be of similar character to an Archean enriched mantle reservoir, but this hypothesis has been difficult to test due to the absence of basalt-born mantle xenoliths from the late Paleozoic to Mesozoic. Late Mesozoic (early Cretaceous) mafic intrusive and volcanic rocks occurring in west Shandong Province within the NCB are characterized by large ion lithophile element (LILE), light rare earth element (LREE) enrichment and high filed strength element (HFSE) depletion (Nb, Zr, Hf and Ti) as well as EM1-like Sr-Nd isotopic ratios (initial ⁸⁷Sr/⁸⁶Sr(i) = 0.7040 to 0.7055 and ε_Nd(i) =-18.9 to -9.2), that originated from an aged and enriched lithospheric mantle. The inferred Mesozoic subcontinental lithospheric mantle (SCLM) mainly comprised chemically refractory peridotites with disseminated phlogopite, completely different from that present in Cenozoic time. The Mesozoic SCLM was geochemically and isotopically different compared with the early Paleozoic kimberlite-born peridotite xenoliths that contain high modal proportions of phlogopite. These older xenoliths have no or insignificant HFSE anomalies but EM2-like isotopic features that might represent the lowermost part of Archean lithosphere. The widespread occurrence of EM1-like Sr-Nd isotopic characteristics in basaltic magmas of west Shandong Province during the late Mesozoic indicates that the most of the Archean lithospheric mantle was progressively removed through thermal-mechanical erosion by a hot convective mantle, and further modified by subsequent partial melting processes in response to extensional tectonics.

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Based on the few reliable analyses available at the time, Wiik (1956) demonstrated that bulk analyses of chondrites plotted along two lines of constant iron content. We have tested Wiik's conclusions based on a statistical analysis of bulk compositions of 550 Antarctic meteorites (Yanai et al., 1995). The distribution of total iron content for chondrites from this larger dataset confirms Wiik's perceptive interpretation and provides a boundary condition for chondritic parent body thermal evolution calculations.

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Clay mineral assemblages in relation to the chemical characteristics of Bajocian-Bathonian shales at G. Al-Maghara, North Sinai, Egypt, have been determined to infer the climatic conditions and the factors regulating their distribution. Mineralogical analyses using XRD revealed the dominance of kaolinite relative to illite and smectite. Quartz, calcite, goethite, feldspars and plagioclase represent the non-clay minerals encountered. Chemical data reflect the enrichment of chemically immobile elements (Al, Ti, Zr and Sc) and the depletion of mobile elements (Fe, Ca, Na, K and Mg). Major element concentrations reflect the dominant mineralogical composition and the weathering history of the source area. Moreover, the enrichment of trace elements (Sc, Zr and partially Cr) could be attributed to the source rock chemistry and its weathering history. High values of the Chemical Index of Alteration (CIA) (Al₂O₃/(Al₂O₃ + CaO + K₂O + Na₂O) × 100) were found. The high proportion of kaolinite associated with the enrichments of immobile particularly major elements (Al and Ti) and the high values of CIA suggest intensive chemical weathering of the source rock under tropical to subtropical humid climatic conditions. The abundance of kaolinite relative to smectite was also influenced by hydraulic sorting and relative sea level changes.

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The seasonal change of the precipitates from the acid coal mine drainages is remarkable in the Taebaek coal field in the middle eastern part of the Korean peninsula. The mineral precipitates in the creeks show various colors such as brownish yellow, white, and reddish brown, depending on the chemical conditions of stream waters. The brownish yellow precipitate consist maily of schwertmannite, the white one of poorly crystalline Al-sulfate, and the reddish brown one of ferrihydrite. Neutralization of acid mine drainage took place by mixing with unpolluted waters and/or buffering by dissolution of carbonate or aluminosilicates. The main factors leading to the seasonal change of precipitates are precipitation of hydroxide mineral, water mixing from adjacent unpolluted branch streams, and water-rock interaction.

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Samples of bentonite layers from altered volcanic ash layers of the Anthering Formation in Salzburg, Austria, which most likely covers the Paleocene/Eocene boundary, were analyzed for their chemical composition. The results of the major and trace element determination confirm the previously suggested appearance from at least two different primary localities. One sample has low abundances in TiO₂ and Ir (0.77 wt.% and 47 ± 16 ppt, respectively), whereas all others have iridium concentrations between 200-450 ppt. On the basis of the chemical composition the bentonite layers are distant equivalents of coeval ash deposits from the Fur and Balder Formation in Denmark and the North Sea, respectively, as was suggested from petrological and mineralogical investigations.

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Radiocarbon dating was performed for the extracted organic fractions (cellulose-rich and humic acid fractions of plant fragment; fulvic acid, humic acid and humin fractions of humus substance) and shell from core sediments of the Erhai Lake, SW China. The ¹⁴C dating results reveal that there are considerable differences, but there apparently is a humic acid ≤ humin < fulvic acid fraction sequence of ¹⁴C age increase. The variability in radiocarbon ages of organic fraction of lake sediment suggests that special caution is necessary when radiocarbon ages of bulk sediments are used. The linear correlation between ¹⁴C age of allochthonous terrestrial macrofossil (plant fragment and shell) and depth indicates roughly a constant sedimentation rate of ca. 0.7 mm yr^-1 in central Erhai Lake since 4500 yr BP. The ¹⁴C ages of the autochthonous humic acid fraction are 210∼4800 yr shift from “the true ¹⁴C age” obtained by interpolating the corresponding horizontal level to the above ¹⁴C age-depth correlation. Such age difference may be alternatively attributed to a uniform reservoir effect (most likely ca. 300 yr). The period with large ¹⁴C age shift synchronizes with the period of changes in δ¹³C and ARM intensity and ARM/susceptibility values.

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