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Carboniferous appinitic intrusions from the northern North China craton: geochemistry, petrogenesis and tectonic implications

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Laser ablation inductively coupled plasma mass spectrometry zircon U-Pb dating and geochemical study document Carboniferous (c. 320-317 Ma) appinitic intrusions from the northern North China craton. The rock suite mainly consists of hornblende diorites and monzodiorites, with an SiO^sub 2^ range from 46.8 to 55.4%. These rocks exhibit high alkali contents, strong enrichment in large ion lithophile elements and light rare earth elements, and depletion in high field strength elements, with radiogenic ^sup 87^Sr/^sup 86^Sr^sub i^ ratios of 0.7058-0.7093, unradiogenic ε^sub Nd^(t) of -9.3 to -13.9 and zircon ε^sub Hf^(t) from -8.5 to -18.4. These geochemical features suggest that their generation may involve a distinctive two-stage process: (1) a precursory metasomatism stage of mantle peridotites by melts from subduction-related sediments; (2) a delayed partial melting stage probably initiated by post-subduction transcurrent movements along pre-existing lithospheric shear zones. These mafic to intermediate intrusions, plus other coeval mafic- ultramafic complexes and high Ba-Sr granites from neighbouring regions, not only witness a heterogeneously enriched subcontinental lithospheric mantle along the northern North China craton, but also attest to a reworking-dominated metacratonic process within a post-subduction transtensional regime. [PUBLICATION ABSTRACT]
An Early Mesozoic transcontinental palaeoriver in South China: evidence from detrital zircon U-Pb geochronology and Hf isotopes

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Detrital zircon geochronology reveals that Late Triassic-Early Jurassic fluvial sandstones from the major basins of the South China Craton have similar age patterns and define four populations at 2.6-2.4 Ga, 2.0-1.7 Ga, 850-700 Ma and 480-210 Ma. The late Palaeoproterozoic group is predominant in all of the five samples, and yielded remarkable age peaks at c. 1.85 Ga. These zircons have ε^sub Hf^(t) values between -22.5 and +3.6, suggesting derivation from reworked Archaean crust and minor juvenile crustal additions in the late Palaeoproterozoic. These characteristics differ from those of the Yangtze Block but correlate well with those of samples from the eastern Cathaysia Block. Palaeocurrent analysis of the Early Mesozoic sandstones shows predominant west- and NW-directed palaeoflows, supporting derivation of the sediments from the Cathaysia Block. The remarkable similarities in provenance signatures and spatial changes of lithofacies of the Triassic-Jurassic around the South China Craton delineate an east-west-trending sedimentary zone extending from Korea to West China. Accumulation of these sediments was probably related to the development of an active continental margin produced by westward subduction of the Palaeo-Pacific Plate. A c. 2000 km long westerly draining transcontinental palaeoriver probably had existed in the Early Mesozoic and fed the basins in Korea, South China and West China. [PUBLICATION ABSTRACT]
Erratum for Faithfull et al., Journal of the Geological Society, London, 169 (2) 115-118

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A global leader in serving libraries of all types, ProQuest LLC (“ProQuest”) supports the breadth of the information community with innovative discovery solutions that power the business of books and the best in research experience. More than a content provider or aggregator, ProQuest is an information partner, creating indispensable research solutions that connect people and information. Through innovative, user-centered discovery technology, ProQuest offers billions of pages of global content that includes historical newspapers, dissertations, and uniquely relevant resources for researchers of any age and sophistication—including content not likely to be digitized by others.
Middle Triassic arc magmatism along the northeastern margin of the Tibet: U-Pb and Lu-Hf zircon characterization of the Gangcha complex in the West Qinling terrane, central China

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The tectonic setting of Mesozoic magmatic complexes in the northeastern margin of the Tibet plateau is disputed, and hence gives rise to uncertainty concerning the tectonic evolution of the northeastern Tibet Plateau and the timing of the closure of the Palaeo-Tethys ocean. The Gangcha complex is typical of these complexes, consisting of andesite, dacite, gabbro, gabbroic diorite, granodiorite, quartz diorite, and diorite with typical chemical traits of continental margin arc rocks. Andesite, gabbroic diorite, and mineralization-associated potassic-altered diorite yield weighted mean ^sup 206^Pb/^sup 238^U ages of 242.1 1.2 Ma, 243.8 1.0 Ma and 234.0 0.6 Ma respectively. Zircon ε^sub Hf^(t) for magmatic grains ranges from -3.5 to +5.7, interpreted to demonstrate that the Gangcha complex contains crustally contaminated mantle magmas. Inherited zircons in the complex yield similar U-Pb ages (777-310 Ma) to the A'nyemaqen composite ophiolite assemblage with ε^sub Hf^(t) of -17.4 to +11.6. This suggests that components of this older ophiolite melted and contributed to the Gangcha complex magmas. Hence the Gangcha complex is considered to have formed as a continental margin arc in northeastern Tibet by northward subduction during consumption of the Palaeo-Tethys ocean. Regionally, it corresponds to the arc magmatism along the eastern and western Kunlun sutures to the west and the Mianlue suture to the east. [PUBLICATION ABSTRACT]
The influence of depositional processes on the porosity of chalk

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Chalk constitutes challenging low-permeability reservoirs with porosity variations attributable to complex interactions between numerous processes. The influence of depositional processes, and thus the value of depositional models to predict porosity, is subject to continuing debate. In this study, a new approach is applied to investigate the influence of depositional and early post-depositional processes on chalk porosity, based on the 303 m thick Upper Cretaceous chalk succession in the Mona-1 core from the Danish North Sea. The influence of depositional processes on porosity is isolated by a mathematical correction of porosity data. Results confirm that mass-transport deposits are on average more porous than pelagites, whereas turbidites are less porous, given similar composition, burial history, and hydrocarbon migration history. The porosity variation between 12 chalk facies suggests that grain packing of the sediment in the consolidated state caused the facies-dependent porosity variation. Bioturbation caused a relatively tight grain packing compared with deposits that escaped bioturbation. Early plastic shear deformation of tightly packed bioturbated units resulted in dilative behaviour, which increased porosity, whereas more loosely packed units responded contractively, resulting in decreased porosity preservation. A firm understanding of chalk facies and thorough facies analyses are thus considered instrumental in chalk reservoir prediction. [PUBLICATION ABSTRACT]
Fracture development and diagenesis of Torridon Group Applecross Formation, near An Teallach, NW Scotland: millennia of brittle deformation resilience?

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The Late Proterozoic Torridon Group Applecross Formation in the foreland of the Moine Thrust Belt, NW Scotland, contains deformation bands, three fracture sets (from oldest to youngest A, B, and L) defined by orientation, crosscutting relations, and progressively less quartz cement in younger sets, and joints. Set A crosscuts deformation bands and strikes north-south. Set B has trimodal orientation defining three linked subsets that formed concurrently. Set L strike ranges from NE-SW to ENE-WSW, in parent crack-wing crack arrays that formed progressively; these are more abundant near small-displacement, oblique-slip faults that offset the overlying Cambrian Eriboll Formation and the Moine Thrust Belt. Applecross sandstones have low fracture abundance, possibly a consequence of low elastic moduli (Young's modulus 2.3-17.0 GPa, most values 6.9 GPa) and moderate to high subcritical crack index (45-78), resulting from compacted softlithic grains and clay-mineral cements. Low abundance contradicts models that postulate persistent incipient failure by subsurface fracture. The fracture sequence resembles that found in the overlying Cambrian Eriboll Formation quartzarenites, implying that no widespread late Proterozoic fracture sets exist in this part of the Applecross Formation, an uneventful record for a rock profoundly resistant to brittle deformation. [PUBLICATION ABSTRACT]
Large-scale, linked drainage systems in the NW European Triassic: insights from the Pb isotopic composition of detrital K-feldspar

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Pb isotopic data from K-feldspars in Middle Triassic (Anisian) sandstones in the Wessex Basin, onshore SW UK, and the East Irish Sea Basin, some 350 km to the north, show that the same grain populations are present. This indicates that the drainage system (the 'Budleighensis' river) feeding these basins originated from the same source/s, most probably the remnant Variscan uplands to the south. Fluvial and aeolian sandstones have the same provenance, suggesting that if water- and wind-driven sands were originally derived from different sources, this has been obscured through reworking prior to final deposition. Significant recycling of feldspar from arkosic sandstones in earlier sedimentary basins can be ruled out. The provenance data agree with previous depositional models, indicating transport distances in excess of 400 km, with a drainage pattern that linked separate basins. This supports the idea that the regional fluvial system was driven by topography and episodic flooding events of sufficient magnitude to overcome evaporation and infiltration over hundreds of kilometres. Importantly, this drainage system appears to have been isolated and independent from those operating contemporaneously to the NW of the Irish and Scottish massifs, where the remnant Variscan uplands apparently exerted no influence on drainage or sand supply. [PUBLICATION ABSTRACT]
Key factors controlling massive graphite deposition in volcanic settings: an example of a self-organized critical system

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Massive graphite deposition resulting in volumetrically large occurrences in volcanic environments is usually hindered by the low carbon contents of magmas and by the degassing processes occurring during and after magma emplacement. In spite of this, two graphite deposits are known worldwide associated with volcanic settings, at Borrowdale, UK, and Huelma, Spain. As inferred from the Borrowdale deposit, graphite mineralization resulted from the complex interaction of several factors, so it can be considered as an example of self-organized critical systems. These factors, in turn, could be used as potential guides for exploration. The key factors influencing graphite mineralization in volcanic settings are as follows: (1) an unusually high carbon content of the magmas, as a result of the assimilation of carbonaceous metasedimentary rocks; (2) the absence of significant degassing, related to the presence of sub-volcanic rocks or hypabyssal intrusions, acting as barriers to flow; (3) the exsolution of a carbon-bearing aqueous fluid phase; (4) the local structural heterogeneity (represented at Borrowdale by the deep-seated Burtness Comb Fault); (5) the structural control on the deposits, implying an overpressured, fluid-rich regime favouring a focused fluid flow; (6) the temperature changes associated with fluid flow and hydration reactions, resulting in carbon supersaturation in the fluid, and leading to disequilibrium in the system. This disequilibrium is regarded as the driving force for massive graphite precipitation through irreversible mass-transfer reactions. Therefore, the formation of volcanic-hosted graphite deposits can be explained in terms of a self-organized critical system. [PUBLICATION ABSTRACT]
Occurrence of inherited supra-subduction zone mantle in the oceanic lithosphere as inferred from mantle xenoliths from Dragon Seamount (southern Tore-Madeira Rise)

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Spinel-bearing peridotite and pyroxenite xenoliths dredged from the Dragon Seamount (southern Tore-Madeira Rise, West Iberia and Morocco margin) give an insight into the composition of the underlying lithosphere. These xenoliths are devoid of evidence of strong host lava-peridotite interaction and re-equilibration or late impregnation in the plagioclase facies. The spinels and pyroxenes from the Dragon peridotites have compositions distinct from those of both lherzolites and harzburgites from the Iberia margin and the Mid-Atlantic Ridge. They display a highly depleted composition, in particular, high Cr-number, up to 0.63 in the spinels, consistent with a melting degree between 12 and 19%. Because of the strong chemical similarities between the Tore-Madeira Rise, Newfoundland peridotites, and peridotites from supra-subduction zones, we propose that the Dragon peridotites formed in a similar context. The pyroxenites display a cumulate texture and are probably a high-temperature-high-pressure cumulate formed by fractional crystallization from a melt. The Tore-Madeira Rise peridotites may represent a former mantle wedge in an oceanic arc, later included into the continental lithosphere and finally tectonically disseminated within the lithosphere during the rifting of the Newfoundland-Iberia continental lithosphere. As a consequence, rifting processes may produce heterogeneities in the oceanic lithosphere and influence isotopic compositions of ocean island basalt-type lavas during plume-lithosphere interactions, as inferred for the southern Tore-Madeira Rise. [PUBLICATION ABSTRACT]
Oxygen isotope variability in conodonts: implications for reconstructing Palaeozoic palaeoclimates and palaeoceanography

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Conodonts have the potential to elucidate the intricacies of Palaeozoic climates, especially if δ^sup 18^O values of single apatitic tooth-like 'elements' can be used to map evolving sea surface temperatures and differentiate oceanic water masses. Their ecological distribution as pelagic and nektobenthic organisms, high-resolution biostratigraphy, and abundance in Cambrian-Triassic rocks qualifies them as potentially robust climate archives. Previous ion microprobe conodont δ^sup 18^O studies have proceeded directly to palaeotemperature interpretation without appreciation of inter- and intra-element variability or post-mortem artefacts. Here, ion microprobe analyses of Ordovician and Silurian conodonts establishes that: intra-element crown tissue δ^sup 18^O typically varies by ≤1[per thousand] (53% of conodonts analysed), is normally ≤2[per thousand] (92% of analyses), and rarely varies by 2-4[per thousand]; δ^sup 18^O can vary across elements, suggesting a microstructural and/or diagenetic control; δ^sup 18^O can vary between species representatives by c. 3[per thousand]; δ^sup 18^O of pelagic and nektobenthic taxa can be offset by 2-3[per thousand]; elements processed with formic acid have highly variable δ^sup 18^O; and thermal alteration does affect δ^sup 18^O. Conodont ion microprobe δ^sup 18^O values are comparable with those of bulk methods, but utilization of material with no consideration of geological context or processing history may introduce significant artefacts. A protocol for future conodont oxygen isotope ion microprobe studies is proposed. [PUBLICATION ABSTRACT]
Conducting Environmental Health Research in the Arabian Middle East: Lessons Learned and Opportunities

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A global leader in serving libraries of all types, ProQuest LLC (“ProQuest”) supports the breadth of the information community with innovative discovery solutions that power the business of books and the best in research experience. More than a content provider or aggregator, ProQuest is an information partner, creating indispensable research solutions that connect people and information. Through innovative, user-centered discovery technology, ProQuest offers billions of pages of global content that includes historical newspapers, dissertations, and uniquely relevant resources for researchers of any age and sophistication—including content not likely to be digitized by others.
Mercury Production and Use in Colonial Andean Silver Production: Emissions and Health Implications

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From:ProQuest LLC

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A global leader in serving libraries of all types, ProQuest LLC (“ProQuest”) supports the breadth of the information community with innovative discovery solutions that power the business of books and the best in research experience. More than a content provider or aggregator, ProQuest is an information partner, creating indispensable research solutions that connect people and information. Through innovative, user-centered discovery technology, ProQuest offers billions of pages of global content that includes historical newspapers, dissertations, and uniquely relevant resources for researchers of any age and sophistication—including content not likely to be digitized by others.
CORRECTION - PDF

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From:ProQuest LLC

Document Overview:

A global leader in serving libraries of all types, ProQuest LLC (“ProQuest”) supports the breadth of the information community with innovative discovery solutions that power the business of books and the best in research experience. More than a content provider or aggregator, ProQuest is an information partner, creating indispensable research solutions that connect people and information. Through innovative, user-centered discovery technology, ProQuest offers billions of pages of global content that includes historical newspapers, dissertations, and uniquely relevant resources for researchers of any age and sophistication—including content not likely to be digitized by others.
Arsenic, Organic Foods, and Brown Rice Syrup

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Document Overview:

A global leader in serving libraries of all types, ProQuest LLC (“ProQuest”) supports the breadth of the information community with innovative discovery solutions that power the business of books and the best in research experience. More than a content provider or aggregator, ProQuest is an information partner, creating indispensable research solutions that connect people and information. Through innovative, user-centered discovery technology, ProQuest offers billions of pages of global content that includes historical newspapers, dissertations, and uniquely relevant resources for researchers of any age and sophistication—including content not likely to be digitized by others.
Migration Associated with Climate Change

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Document Overview:

A global leader in serving libraries of all types, ProQuest LLC (“ProQuest”) supports the breadth of the information community with innovative discovery solutions that power the business of books and the best in research experience. More than a content provider or aggregator, ProQuest is an information partner, creating indispensable research solutions that connect people and information. Through innovative, user-centered discovery technology, ProQuest offers billions of pages of global content that includes historical newspapers, dissertations, and uniquely relevant resources for researchers of any age and sophistication—including content not likely to be digitized by others.

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Carboniferous appinitic intrusions from the northern North China craton: geochemistry, petrogenesis and tectonic implications

An Early Mesozoic transcontinental palaeoriver in South China: evidence from detrital zircon U-Pb geochronology and Hf isotopes

Erratum for Faithfull et al., Journal of the Geological Society, London, 169 (2) 115-118

Middle Triassic arc magmatism along the northeastern margin of the Tibet: U-Pb and Lu-Hf zircon characterization of the Gangcha complex in the West Qinling terrane, central China

The influence of depositional processes on the porosity of chalk

Fracture development and diagenesis of Torridon Group Applecross Formation, near An Teallach, NW Scotland: millennia of brittle deformation resilience?

Large-scale, linked drainage systems in the NW European Triassic: insights from the Pb isotopic composition of detrital K-feldspar

Key factors controlling massive graphite deposition in volcanic settings: an example of a self-organized critical system

Occurrence of inherited supra-subduction zone mantle in the oceanic lithosphere as inferred from mantle xenoliths from Dragon Seamount (southern Tore-Madeira Rise)

Oxygen isotope variability in conodonts: implications for reconstructing Palaeozoic palaeoclimates and palaeoceanography

Conducting Environmental Health Research in the Arabian Middle East: Lessons Learned and Opportunities

Mercury Production and Use in Colonial Andean Silver Production: Emissions and Health Implications

CORRECTION - PDF

Arsenic, Organic Foods, and Brown Rice Syrup

Migration Associated with Climate Change