101 research outputs found
Geochemistry of cold seeps - Fluid sources and systematics
Emanation of fluids at cold seeps, mud volcanoes, and
other types of submarine seepage structures is a typical
phenomenon occurring at continental margins worldwide.
They represent pathways along which volatiles and solutes are
recycled from deeply buried sediments into the global ocean,
and hence they may be considered as a potentially important
link in global geochemical cycles.
In this contribution we present geochemical data from
various geological and tectonic settings such as the Gulf of
Cadiz, the convergent margin off Central America, and/or the
Black Sea and provide approaches how to systemize available
data sets. Clay-mineral dewatering plays a central role in
terms of fluid-mobilization from greater depth, however,
resulting cold seep fluids are typically very different from
each other and cover a large range of geochemical signatures.
This is is due to variations in control parameters such as the
type and thickness of the sediment cover, thermal conditions,
extension of fluid pathways, and the potential for secondary
overprinting. For example, freshened fluids emanating at cold
seeps off Costa Rica indicate dewatering and related
geochemical reactions in subducting sediments, while fluids
sampled at mud volcanoes in the Gulf of Cadiz provide
evidence for a high-temperature fluid source originating in the
underlying oceanic basement. The latter finding provides
evidence for a hydrological connection between buried
oceanic crust and the water column even at old crustal ages.
Varius geochemical tracers were proposed in the past to
decipher relevant processes in the subsurface. In a recent
systematic study, Scholz et al. [1] demonstrated the general
use of Li, reflecting the temperature-dependent isotope
fractionation during early diagenetic Li uptake and burial
diagenetic Li release from sediments. However, additional
approaches are required in order to provide robust geochmical
interpretations of cold seep fluids
Manganreiche Sedimente im Ordovizium: ein paläogeographischer Proxy für Avalonia
kein Abstract vorhande
Plume–lithosphere interactions and LIP-triggered climate crises constrained by the origin of Karoo lamproites
We identified a ca. 180 Ma diamondiferous lamproite event in Zambia, establishing a link between ultrapotassic
volcanism and the early Jurassic Karoo flood basalt province of sub-Saharan Africa. The cratonic lamproites
erupted through the Permo–Triassic Luangwa Rift structure, but MgO-rich ultrapotassic magma formation was
unrelated to rifting and triggered by plume–lithosphere interactions during the Karoo LIP event. Elevated
Li–Zn–Ti concentrations in magmatic olivine (up to 18.5 ppm Li at 86–90 mol.% forsterite) and strong
Sr–Nd–Hf–Pb isotopic enrichment of the host lamproites (
87Sr/86Sr = 0.70701–0.70855, εNd = − 10.8 to − 10,
εHf = − 20.3 to − 19.1, 206Pb/204Pb = 16.8–17.5) suggest partial melting of phlogopite-metasomatized lithospheric mantle domains, at approximately 180–200 km depth. The mantle-like δ7
Li values (+2.8 to +5.7‰) of
the most pristine lamproite samples are compatible with source enrichment by asthenosphere-derived melts,
without significant involvement of recycled sedimentary components. This geochemical fingerprint stands in
sharp contrast to the negative δ7
Li compositions of primitive K-rich volcanic rocks from collision zone settings,
where the shallow mantle sources contain recycled sediment.
Isotope modelling demonstrates that the sub-Saharan lamproites originate from a MARID-style metasomatized
peridotitic mantle source that underwent incompatible element enrichment at ca. 1 Ga, during tectonic activity
associated with Rodinia supercontinent formation. Plume-sourced basaltic and picritic magmas of the 180 Ma
Karoo LIP interacted with such K-rich hydrous lithospheric mantle domains, thereby attaining enriched
incompatible element and radiogenic isotope compositions. Nd–Hf isotope mass balance suggests that up to 25%
of MARID-sourced lamproite melt component contributed to some of the high-Ti flood volcanic units.
Although large quantities of volatiles can be transferred from Earth’s mantle to the atmosphere via plume–lithosphere interactions, it is unlikely that outgassing of mantle-sourced sulphur can exceed the climatic
impact caused by the release of much more abundant carbon from thick continental roots. Thus, the excess SO2
required to account for transient atmospheric cooling during the early Jurassic, coincident with the Karoo LIP
event, must have had a thermogenic origin near the surface of Earth
Magmatic-hydrothermal fluid evolution of the tin-polymetallic metallogenic systems from the Weilasituo ore district, Northeast China
The large Weilasituo Sn-polymetallic deposit is a recent exploration discovery in the southern Great Xing’an Range, northeast China. The ore cluster area shows horizontal mineralization zoning, from the inner granite body outward, consisting of high-T Sn–W–Li mineralization, middle-T Cu–Zn mineralization and peripheral low-T Pb–Zn–Ag mineralization. However, the intrinsic genetic relationship between Sn-W-Li mineralization and peripheral vein-type Pb–Zn–Ag–Cu mineralization, the formation mechanism and the deep geological background are still insufficiently understood. Here, we use fluid inclusions, trace elements concentrations in quartz and sphalerite, and H–O isotope studies to determine the genetic mechanism and establish a metallogenic model. Fluid inclusion microthermometry and Laser Raman spectroscopic analysis results demonstrates that the aqueous ore-forming fluids evolved from low-medium salinity, medium–high temperature to low salinity, low-medium temperature fluids. Laser Raman spectroscopic analysis shows that CH4 is ubiquitous in fluid inclusions of all ore stages. Early ore fluids have δ18OH2O (v–SMOW) values from + 5.5 to + 6.2‰ and δD values of approximately − 67‰, concordant with a magmatic origin. However, the late ore fluids shifted toward lower δ18OH2O (v–SMOW) (as low as 0.3‰) and δD values (~ − 136‰), suggesting mixing between external fluids derived from the wall rocks and a contribution from meteoric water. Ti-in-quartz thermometry indicates a magmatic crystallization temperature of around 700 °C at a pressure of 1.5 kbar for the magmatic ore stage. Cathodoluminescence (CL) imaging and trace element analysis of quartz from a hydrothermal vug highlight at least three growth episodes that relate to different fluid pulses; each episode begins with CL-bright, Al-Li-rich quartz, and ends with CL-dark quartz with low Al and Li contents. Quartz from Episode 1 formed from early Sn-(Zn)-rich fluids which were likely derived from the quartz porphyry. Quartz from episodes 2 and 3 formed from Zn-(Sn)-Cu-rich fluid. The early magmatic fluid is characterized by low fS2. The SO2 produced by magma degassing reacted with heated water to form SO42−, causing the shift from low fS2 to high fS2. The SO42− generated was converted to S2– by mixing with CH4-rich, Fe and Zn-bearing external fluid which led to late-stage alteration and dissolution of micas in vein walls, thus promoting crystallization of pyrrhotite, Fe-rich sphalerite and chalcopyrite and inhibiting the precipitation of anhydrite. This study shows that ore formation encompassed multiple episodes involving steadily evolved fluids, and that the addition of external fluids plays an important role in the formation of the later Cu–Zn and Ag–Pb–Zn mineralization in the Weilasituo ore district
Atud Gabbro-Diorite Complex: Glimpse of the Cryogenian Mixing, Assimilation, Storage, and Homogenization Zone beneath the Eastern Desert of Egypt
We analysed gabbroic and dioritic rocks from the Atud igneous complex in the Eastern Desert of Egypt to understand better the formation of juvenile continental crust of the Arabian–Nubian Shield. Our results show that the rocks are the same age (U–Pb zircon ages of 694.5 ± 2.1 Ma for two diorites and 695.3 ± 3.4 Ma for one gabbronorite). These are partial melts of the mantle and related fractionates (εNd₆₉₀ = +4.2 to +7.3, ⁸⁷Sr/⁸⁶Sr_i = 0.70246–0.70268, zircon δ¹⁸O ∼ +5‰). Trace element patterns indicate that Atud magmas formed above a subduction zone as part of a large and long-lived (c. 60 myr) convergent margin. Atud complex igneous rocks belong to a larger metagabbro–epidiorite–diorite complex that formed as a deep crustal mush into which new pulses of mafic magma were periodically emplaced, incorporated and evolved. The petrological evolution can be explained by fractional crystallization of mafic magma plus variable plagioclase accumulation in a mid- to lower crustal MASH zone. The Atud igneous complex shows that mantle partial melting and fractional crystallization and plagioclase accumulation were important for Cryogenian crust formation in this part of the Arabian–Nubian Shield
Tumor markers in breast cancer - European Group on Tumor Markers recommendations
Recommendations are presented for the routine clinical use of serum and tissue-based markers in the diagnosis and management of patients with breast cancer. Their low sensitivity and specificity preclude the use of serum markers such as the MUC-1 mucin glycoproteins ( CA 15.3, BR 27.29) and carcinoembryonic antigen in the diagnosis of early breast cancer. However, serial measurement of these markers can result in the early detection of recurrent disease as well as indicate the efficacy of therapy. Of the tissue-based markers, measurement of estrogen and progesterone receptors is mandatory in the selection of patients for treatment with hormone therapy, while HER-2 is essential in selecting patients with advanced breast cancer for treatment with Herceptin ( trastuzumab). Urokinase plasminogen activator and plasminogen activator inhibitor 1 are recently validated prognostic markers for lymph node-negative breast cancer patients and thus may be of value in selecting node-negative patients that do not require adjuvant chemotherapy. Copyright (C) 2005 S. Karger AG, Basel
Isotopic evidence (<sup>87</sup>Sr/<sup>86</sup>Sr, δ<sup>7</sup>Li) for alteration of the oceanic crust at deep-rooted mud volcanoes in the Gulf of Cadiz, NE Atlantic Ocean [(Sr-87/Sr-86, delta Li-7) ]
The chemical and isotopic composition of pore fluids is presented for five deep-rooted mud volcanoes aligned on a transect across the Gulf of Cadiz continental margin at water depths between 350 and 3860 m. Generally decreasing interstitial Li concentrations and Sr-87/Sr-86 ratios with increasing distance from shore are attributed to systematically changing fluid sources across the continental margin. Although highest Li concentrations at the near-shore mud volcanoes coincide with high salinities derived from dissolution of halite and late-stage evaporites, clayey, terrigenous sediments are identified as the ultimate Li source to all pore fluids investigated. Light delta Li-7 values, partly close to those of hydrothermal vent fluids (delta Li-7: +11.9 parts per thousand), indicate that Li has been mobilized during high-temperature fluid/sediment or fluid/rock interactions in the deep sub-surface. Intense leaching of terrigenous clay has led to radiogenic Sr-87/Sr-86 ratios (similar to 0.7106) in pore fluids of the near-shore mud volcanoes. In contrast, non-radiogenic Sr-87/Sr-86 ratios (similar to 0.7075) at the distal locations are attributed to admixing of a basement-derived fluid component, carrying an isotopic signature from interaction with the basaltic crust. This inference is substantiated by temperature constraints from Li isotope equilibrium calculations suggesting exchange processes at particularly high temperatures (>200 degrees C) for the least radiogenic pore fluids of the most distal location.Advective pore fluids in the off-shore reaches of the Gulf of Cadiz are influenced by successive exchange processes with both oceanic crust and terrigenous, fine-grained sediments, resulting in a chemical and isotopic signature similar to that of fluids in near-shore ridge flank hydrothermal systems. This suggests that deep-rooted mud volcanoes in the Gulf of Cadiz represent a fluid pathway intermediate between mid-ocean ridge hydrothermal vent and shallow, marginal cold seep. Due to the thicker sediment coverage and slower fluid advection rates, the overall geochemical signature is shifted towards the sediment-diagenetic signal compared to ridge flank hydrothermal environments. (C) 2009 Elsevier Ltd. All rights reserved
Defining the critical hurdles in cancer immunotherapy
Scientific discoveries that provide strong evidence of antitumor effects in preclinical models often encounter significant delays before being tested in patients with cancer. While some of these delays have a scientific basis, others do not. We need to do better. Innovative strategies need to move into early stage clinical trials as quickly as it is safe, and if successful, these therapies should efficiently obtain regulatory approval and widespread clinical application. In late 2009 and 2010 the Society for Immunotherapy of Cancer (SITC), convened an "Immunotherapy Summit" with representatives from immunotherapy organizations representing Europe, Japan, China and North America to discuss collaborations to improve development and delivery of cancer immunotherapy. One of the concepts raised by SITC and defined as critical by all parties was the need to identify hurdles that impede effective translation of cancer immunotherapy. With consensus on these hurdles, international working groups could be developed to make recommendations vetted by the participating organizations. These recommendations could then be considered by regulatory bodies, governmental and private funding agencies, pharmaceutical companies and academic institutions to facilitate changes necessary to accelerate clinical translation of novel immune-based cancer therapies. The critical hurdles identified by representatives of the collaborating organizations, now organized as the World Immunotherapy Council, are presented and discussed in this report. Some of the identified hurdles impede all investigators; others hinder investigators only in certain regions or institutions or are more relevant to specific types of immunotherapy or first-in-humans studies. Each of these hurdles can significantly delay clinical translation of promising advances in immunotherapy yet if overcome, have the potential to improve outcomes of patients with cancer
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