Barren Zone Research Articles

Regional differences in lead (Pb) and tetracycline (TC) binding behavior of sediment dissolved organic matter (SDOM): Effects of DOM heterogeneity and microbial degradation

Lake Nansi, primarily dominated by macrophytes, faces threats from heavy metals and antibiotics due to human activity. This study investigated sediment dissolved organic matter (SDOM) characteristics and complexation of lead (Pb) and tetracycline (TC) in barren zone (BZ) and submerged macrophytes zone (PZ). Additionally, a microbial degradation experiment was conducted to examine its impact on the regional variations in complexation. SDOM abundance and protein-like materials in PZ was significantly greater than in BZ, indicating a probable contribution from the metabolism and decomposition of submerged macrophytes. Both zones exhibited a higher affinity of SDOM for Pb compared to TC, with all four components participating in Pb complexation. Protein-like materials in PZ had a higher binding ability (LogKPb=4.19 ± 1.07, LogKTC=3.89 ± 0.67) than in BZ (LogKPb=3.98 ± 0.61, LogKTC=3.69 ± 0.13), suggesting a potential presence of organically bound Pb and TC due to the higher abundance of protein-like materials in PZ. Although microbial communities differed noticeably, the degradation patterns of SDOM were similar in both zones, affecting the binding ability of SDOM in each. Notably, the fulvic-like component C4 emerged as the dominant binding material for both Pb and TC in both zones. Degradation might increase the amount of organically bound TC due to the increase in the LogKTC.

Mechanism of beryllium mineralization in a granite-pegmatite system: Constraints from ore geology and beryl mineralogy of the large Arskartor Be-Nb-Mo deposit, southern Chinese Altai

The Arskartor Be-Nb-Mo deposit is the second largest Be deposit in the Chinese Altai, NW China, which hosts over 11,000 tons of BeO resource. The muscovite-albite granite and rare-metal pegmatite in the ore district are spatially and temporally coexisted and both are beryllium mineralized. The muscovite-albite granitic stock can be divided into a barren zone and a Be-mineralized zone. The pegmatite shows an well-developed internal zone including the layered muscovite-quartz-albite zone, (lower) beryl-muscovite-quartz zone, quartz core, (hanging) beryl-muscovite-quartz zone, and muscovite-quartz-microcline zone. Beryl is the dominant Be-bearing mineral and mainly occurs in the Be-mineralized granite, the layered muscovite-quartz-albite and the beryl-muscovite-quartz zones of the pegmatite. Subhedral to euhedral beryl in the Be-mineralized granite is interstitial to or intergrown with rock-forming minerals. In contrast, beryl crystals in the pegmatite are coarser in grain size and more euhedral in shape, and mainly coexist with coarse “booked” muscovite and blocky quartz. Concentrations of Li, Cs and Na/Li ratios of beryl are 184–760 ppm, 218–1996 ppm, and 2.13–21.3, respectively. The progressive variations of incompatible elements compositions and Na/Li ratios are consistent with the fractional crystallization mechanism of the granite-pegmatite system. Paragenesis and internal structure of beryl suggest nonequilibrium crystallization of a relatively incompatible elements and fluxes-enriched late granitic melt, generated the coarse-grained Be-mineralized granite. With the progressive enrichment of incompatible and fluxing elements and decreasing temperature, liquidus overcooling was achieved and generated the aplite and immediate zoned pegmatite that hosts abundant beryl. Moreover, the differentiating pegmatitic melt with varying amounts of aqueous fluids at different melt fractions, likely resulted in heterogeneous distribution of beryllium and subsequent variable amounts of beryl crystallization in different internal zones. The exsolution of aqueous fluids from the residual pegmatitic melt resulted in Mo-mineralization and related hydrothermal alteration. Consequently, both protracted fractional crystallization and subsolidus processes contributed the formation of the Arskartor granite-pegmatite system with Be-polymetallic mineralization.

Short-wavelength infrared characteristics and composition of white mica in the Demingding porphyry Cu-Mo deposit, Gangdese belt, Tibet: Implications for mineral exploration

The Demingding Cu–Mo deposit, found in the eastern Gangdese metallogenic belt in China, has a significant exploration potential. Detailed field studies coupled with short-wavelength infrared (SWIR) spectroscopy and electron probe micro analyses (EPMA) identified a total of 15 alteration minerals such as white mica group minerals, chlorite, kandite, and smectite groups. The study also discovered the spatial distribution of alteration zone patterns, including phyllic, propylitic, and intermediate argillic alterations. Furthermore, variations were observed in the Al-OH absorption position (Pos2200) of the white mica group with variable Al-Si-Fe-Mg content. Most of the white micas in the ore zone were muscovitic series, whereas the barren zone contained phengitic series micas. Some micas have undergone a transition to illite due to low-temperature alteration overprinting. The western part of the deposit exhibited lower Pos2200, higher SWIR-IC, and higher Dep2200 values, implying an intense phyllic alteration and higher paleotemperatures. These characteristics suggest that the area is in close proximity to the hydrothermal center and fluid channel. Therefore, it was identified as an exploratory target for buried copper ore bodies. The SWIR spectra of the white mica group can be used for exploration in other similar porphyry deposits. Under acidic conditions, shorter Pos2200 and higher SWIR-IC can be used as indicators for hydrothermal or mineralization centers.

Mitigating Raman relaxation for high-temperature single-molecule magnets

Previous studies on how to prolong the relaxation times of single-molecule magnets (SMMs) focus on mitigating the quantum tunneling effect. However, recent progress shows that Raman relaxation is more critical. Yet, the study of the Raman process turns out to be a barren zone for molecular systems and requires further exploration.

A mineralogical-geomorphological terrain analysis of hotspot volcanic islands - The missing link between carbonatite- and pegmatite Nb-F-Zr-Li-Be-bearing REE deposits and new tools for their exploration (Canary Islands Archipelago, Spain)

Two geoscientific disciplines (mineralogy, geomorphology) which are placed far apart from each other are selected to forge a genetic tie line between carbonatite- and agpaitic pegmatite-hosted REE deposits, likewise far away from each other. The Canary Islands Archipelago, Spain, (=CIA) is known as a hotspot hosting REE among other rare elements (28 Ma to the Recent) in volcanic landforms. This rare metal metallogenic province is connected to a carbonatite-pegmatite REE province in NNW Africa. It is a binary mineralization with one hub covering SW Tenerife and NE La Gomera that is characterized by an alkali-magmatite-related REE system with pegmatitic syenites at depth and another hub covering Central - and NW Fuerteventura where (meta) carbonatites are exposed and form a bridge to the REE-bearing carbonatites and pegmatites on mainland Africa, Morocco.The REE concentration took place in four stages which differ from each as with regard to their landscape and mineralogy:(1)magmatic calcic-carbonatites with REE-bearing apatite (28 to 24 Ma)(2)calcic-carbonatites, alkali magmatites with REE phosphate and carbonates (contact-metamorphic - metasomatic, epithermal) (19 to 4 Ma)(3)alkali magmatites with hydroxyl-group-bearing REE phosphates, REE oxides, Fe oxide, Fe-Cu sulfides, kaolinite-halloysite, and REE-APS minerals (epithermal) (5 to 0.3 Ma)(4)pyroclastic and volcanic rocks with smectite, kaolinite, REE-bearing silicates and oxides (auto-metasomatic) and a variegated series of more than 100 REE-, Nb-, F-, Zr-, Li- and Be minerals which are diagnostic for carbonatite- and/or alkali-magmatites pegmatitic systems at depth (<0.6 Ma).This REE mineralization of the CIA extending into on-shore Morocco is akin to the REE mineralization recorded from titanomagnetite–magnetite–apatite-REE- deposits in carbonatite-alkaline complexes in N Europe with the reference catena-deposits Kiruna-Sokli-Chibina (Sweden, Finland, Russia). The NNW African REE metallogenic province shows from E to W four geodynamic zones:(1)Atlas Mts. REE - Fe Province (thick continental crust of the mainland),(2)Fuerteventura (thick continental shelf pinching out to the W),(3)Gran Canaria – Tenerife-La Gomera (thin continental shelf to oceanic crust),(4)El Hierro – La Palma (barren zone as to REE oceanic crust).The REE mineralization starts off with syn- to post-kinematic en-echelon strike-slip faulting followed by a clock-wise rotation of its morpho-structural elements and wanes with a reactivation of NE-SW morpho-structural elements as normal faults attesting to a decoupling from the Atlas Mts. deformation and intensification of an individual hotspot mineralization. The land-forming processes and the resultant volcanic landscape are genetically linked to the REE-, Nb-, F-, Zr-, Li-, and Be mineralization: mass wasting (MW) > fluvial drainage (FD) > lacustrine (L), ≥ coastal marine (CM) ≫ aeolian (A). Each of the land-forming processes provides marker landforms indicative processes relevant for rare element accumulations:MW: thrusting, exhumation of the level of primary REE mineralization, zones of structural weakness,FD: morphostratigraphic tracing of fertile bedrocks, demarcation of ring dyke complexes and zones of contact-metamorphic and contact-metasomatism, zones of ground- and surface water stagnancy, zones of strong argillitization and hematitization,CM: exhumation, providing marker heavy minerals and gravel lithoclasts,L: rifting structures, zones of volcanic and epithermal activity,A: pathfinder heavy minerals.The methodological approach taken throughout this composite study (field- and laboratory-based research work combined with a meticulous review of the mineralogical, chronological and geological regional literature) is that of a mineralogical-geomorphological terrain analysis.Numerical geomorphological and sedimentological parameters are of assistance during remote sensing and ground follow-up mapping: (1) elevated degree of sinuosity and argillitization, (2) numerical classification of the terrain based on dip of slope plus altitude, (3) gravel analysis based on granulometry, morphology and situmetry (GMS technique) for provenance and environment analysis. The morphodynamic elements have a high preservation potential and are not blurred by morphoclimatic ones so that the mineralogical terrain analysis can be taken as a trusted exploration tool for REE.Geodynamic and volcanic activity are the driving forces and prevail over the climate impact in shaping the landscape. Therefore, landforms in combination with compositional data from mineralogy can shed some light on the origin of REE-Nb-F-Zr-Li- Be mineral associations on hotspot volcanic islands. This holistic approach can also be taken to different mineral commodities elsewhere in the world given a low maturity of the landscape in the target area. It can also be used for submarine landforms in and around an archipelago simply by minero-stratigraphic correlation from land to sea. The mineralogical terrain analysis as applied in the current study is not a fixed methodological construct but open also for replacements and supplements by e.g. geophysics.

The Middle-Upper Eocene benthic foraminifera from north-west Fayoum area, Egypt: Paleoecology and their similarity to the Tethyan provinces

This study deals with the Middle–Late Eocene benthic foraminiferal assemblage from the Um Rigl succession that is exposed in the northwest of Fayoum area, Egypt. Stratigraphically, two rock units are recognized from base to top as the Gehannam Formation and Birket Qarun Formation. The examination of benthic foraminiferal community identifies 63 species belonging to 36 genera, 22 families and four suborders. Their distribution aids to recognize one benthic foraminiferal biozone, Bulimina jacksonensis-Uvegerina jacksonensis Zone. To detect the paleocological conditions that prevailed during the deposition of the studied succession, a quantitative analysis is done on the foraminiferal assemblage, including the number of taxa, the relative abundances of the recorded suborders, calcareous species, agglutinated species and common species. The morphology of benthic foraminiferal tests is strongly associated with their microhabitat preferences. Therefore, the percentages of epifaunal and infaunal species are also calculated to detect the level of oxygenation. Accordingly, two ecozones are established, ecozone 1 represents the Gehannam Formation, whereas ecozone 2 represents the Birket Qarun Formation (excluding the barren zone in the upper part). Ecozone 1 is dominated by calcareous species (90–100%) and infaunal species (38–99%), while epifaunal species range from 2 to 62%. The most abundant taxa are Bolivina, Bulimina, Uvigerina, Nonion and Lenticulina. Therefore, the ecozone 1 was deposited under an inner-outer neritic environment, with normal salinity and eutrophic to mesotrophic conditions. On the other side, ecozone 2 is characterized by changes in the composition of foraminiferal assemblage, where infaunal species dominate the base of this ecozone, followed by a strong decline in the middle part and then increase again in the upper part. Also, a notable increase in epifaunal species is documented in this ecozone. This variation in foraminiferal assemblage reflects changes in water depth and oxygen content. Consequently, ecozone 2 was deposited under an inner to middle neritic environment, with normal salinity and mesotrophic to oligotrophic conditions. Regarding the paleobiogeographic outline, the results of multivariate analyses indicate that the Egyptian species show a strong similarity to those from the Southern Tethyan Province (Tunisia and Libya), whereas they show a reasonable similarity to the Western Tethyan Province (Spain, Italy, France). This deduction reflects a probable marine connection between both provinces during Eocene.

A microfossil assemblage from the Ediacaran Doushantuo Formation in the Shennongjia area (Hubei Province, South China): Filling critical paleoenvironmental and biostratigraphic gaps

Microfossils of the Ediacaran Doushantuo Formation in South China provide an important window onto the rapid diversification of marine eukaryotes after the terminal Cryogenian global glaciation. They also offer key data in the biostratigraphic subdivision and correlation of the lower–middle Ediacaran System. Previously published Doushantuo microfossils in South China were mostly from intra-shelf facies in the Yangtze Gorges area, shelf margin facies in the Weng’an area, and upper slope facies in the Zhangjiajie area, whereas paleontological data from shallow-water inner shelf facies have been rarely documented. In addition, previous data from South China leave a “barren zone” associated with the negative δ13Ccarb excursion EN2 that impedes biostratigraphic correlation. To address these environmental and stratigraphic gaps, we conducted an integrated chemostratigraphic and biostratigraphic analysis of the Doushantuo Formation at the inner shelf Lianhuacun section in the eastern Shennongjia area of Hubei Provence, South China. The Lianhuacun fossils are preserved in chert nodules/bands of the lower Doushantuo Formation, precisely in a chemostratigraphic interval identified as EN2, indicating that the so-called “barren zone” is likely a taphonomic artifact. A total of 33 genera and 82 species are identified, including a new genus (Duospinosphaera gen. nov.) and seven new species (Duospinosphaera shennongjiaensis sp. nov., D. biformis sp. nov., Jixiania retorta sp. nov., Mengeosphaera mamma sp. nov., Sinosphaera exilis sp. nov., Tanarium columnatum sp. nov., and Weissiella concentrica sp. nov.). The Lianhuacun acanthomorphic acritarchs can be broadly assigned to the third microfossil assemblage zone (i.e., the Tanarium conoideum – Cavaspina basiconica Assemblage Zone) recognized on the basis of the Weng’an biota that is correlated with upper Member II of Doushantuo Formation in the Yangtze Gorges area, consistent with chemostratigraphic correlation between the Shennongjia and Yangtze Gorges areas. Thus, the so-called “barren zone” may be a poorly preserved part of the third microfossil assemblage zone. Alternatively, it may represent a new and yet unnamed microfossil assemblage zone between the third and the overlying Tanarium pycnacanthum – Ceratosphaeridium glaberosum Assemblage Zone. Regardless, the new data presented here fill important gaps in the geographical, paleoenvironmental, and stratigraphic distributions of Ediacaran acanthomorphic acritarchs in South China. As such, they facilitate integrative chemostratigraphic and biostratigraphic correlation of Ediacaran strata at regional and global scales.

Influence mechanism of Au layer thickness on wettability of Sn–Ag–Cu solder on heated ENIG pads

Solder wettability on substrate is an issue for the electronic devices. In this present, the heated Cu pads with ENIG finish was selected as the study object. Effect of Au layer thickness on ENIG surface morphology, Ni distribution and wettability of Sn-3.0Ag-0.5Cu solder was investigated. An acceptable morphology with nanoscale fluctuation for ENIG surface was achieved, with the absence of interface cracking, pits, holes. Ni diffused from Ni layer to Au surface during heating process, then reacted with the ambience to form Ni oxides, the fraction was increased with the increasing Au layer thickness. The Ni oxides inhibited the interfacial reaction between Sn-3.0Ag-0.5Cu and Ni during reflow, and remained to the interface. It resulted in the formation of “barren zones”, where without any intermetallic compounds. With Au layer thickness increased, “barren zones” was shrunk until to disappear. The “barren zones” was responsible to the wettability of Sn solder. The more “barren zones”, the poor wettability.

Pseudoreticulate-Subreticulate-Reticulate Nummulites and their possible evolution in the middle Eocene-lower Oligocene succession of Surat-Bharuch, Gujarat India

A biostratigraphically well constrained middle Eocene to lower Oligocene shelf succession (ca. 33 m) of the Amravati Formation in the Vagalkhod-Dinod area of Surat-Bharuch Districts, Gujarat, India contains Nummulites having varied septal filaments, among which complicated filaments show progressive changes in the succession. Complications by the intersection of filaments with spiral laminae/ridge, bifurcation of filaments at low angle and joining by transverse trabeculae, and bifurcation and re-joining of filaments at high and varied angles, and consecutive bifurcation and trifurcation of filaments allowed their categorization in different species. Successive appearances of pseudoreticulate filaments (Nummulites acutus, Nummulites broachensis and Nummulites longilocula), subreticulate filaments (Nummulites hormoensis and Nummulites ptukhiani) and reticulate filaments (Nummulites fabianii, Nummulites retiatus and Nummulites fichteli) reflect gradual complication with time, producing a bioseries that is also manifested by changes in canals and equatorial chambers. The eight species of Nummulites are differentiated and described within the pseudoreticulate subreticulate- reticulate group and based on their stratigraphic distribution, seven zones in ascending order namely, the Nummulites acutus Assemblage Zone, Nummulites broachensis Range Zone, SRG Barren zone, Nummulites hormoensis-Nummulites fabianii Interval Zone, Nummulites fabianii Range Zone, Nummulites fabianii-Nummulites retiatus Interval Zone and Nummulites fichteli Range Zone are recognized and described. The zones are tentatively correlated with the SB zones and their ages are assigned by planktonic foraminiferal zones. Complexity of septal filaments within the Nummulites of the succession began with the development of pseudoreticulation (by the intersection of radial filaments with spiral laminae) during the late Lutetian; afterward during the early Bartonian Stage bifurcation develops in a septal filament along with occasional joining by transverse trabeculae; subreticulation remained restricted to the late Bartonian,while reticulation appeared at the beginning of the Priabonian to flourish during the Priabonian to mid Rupelian.The bioseries by septal filaments shows three evolutionary trends in these species: 1) evolution of N. acutus to N. fichteli through N. broachensis-N. hormoensis-N. ptukhiani-N. fabianii; besides acquiring complication of septal filaments this trend shows a general increase in the size of the proloculus, an increase of the size of the B-form, increasing complication in canals, and lowering the height of equatorial chambers concomitant with the increase of length; 2) evolution of N. acutus to N. broachensis to N. longilocula; this trend is restricted to the pseudoreticulate group; discerning changes involve connecting adjacent septal filaments by transverse trabeculae and spiral laminae, and development of rudimentary mesh of septal filaments, complication in canals and slit-like long equatorial chambers; 3). evolution of N. hormoensis to N. retiatus; changes involve in the development of reticulation from subreticulate septal filaments, decrease in the height of chambers, complication in canals, and development of laminae and mesh as grooves. Nummulites acutus is ancestral to all the discussed species. The evolution of Nummulites leading to complicated septal filaments is known during the corresponding span in the Mediterranean region, East African region, and a few locations in western European and southeast Asian regions, but the trends of evolution as studied in the Amravati Formation differs in the distinct developments of pseudoreticulate lineage, N. ptukhiani as an intermediate evolutionary form between N. hormoensis and N. fabianii, and in the development of complex subreticulation from a simple one. The studied succession is the only one of its kind in the Indian region to have successive development of pseudoreticulate-subreticulate-reticulate Nummulites across the Lutetian/Bartonian, Bartonian/Priabonian and Priabonian/Rupelian boundaries.

Evolution and Li Mineralization of the No. 134 Pegmatite in the Jiajika Rare-Metal Deposit, Western Sichuan, China: Constrains from Critical Minerals

The Jiajika rare-metal deposit located in western Sichuan Province (China) is renowned as the largest lithium deposit in Asia, and the No. 134 pegmatite dike is the largest lithium pegmatite under mining conditions in the area. On the basis of a detailed characterization of textures and minerals in the Jiajika No. 134 pegmatite, two zones (the barren Zone I and the spodumene Zone II) and three subzones (Zone II was subdivided into microcrystalline, medium-fine grained and coarse-grained spodumene zones) have been identified. The detailed mineralogical characteristics of lithium minerals and other indicator minerals from each zone were evaluated by EPMA for illustrating the magmatic–hydrothermal evolution and the cooling path of the Jiajika No. 134 pegmatite. From the outer zone inwards, grain size gradually increased, the typical graphic pegmatite zone was absent, and spodumene randomly crystallized throughout nearly the whole pegmatite body. This evidence indicated a Li-saturated melt prior to pegmatite crystallization, which could be the main cause of the super-large-scale Li mineralization of the Jiajika No. 134 pegmatite. A comparison of the Cs content between primary beryl in the Jiajika No. 134 pegmatite and other important Li-Cs-Ta pegmatites in the world indicates that No. 134 pegmatite shows a high degree of fractional crystallization. The evolution of mica species from muscovite to Li-micas from Zone I to Zone II marks the transition from the magmatic to the hydrothermal stage in pegmatite evolution. The absence of individual lepidolite and the relatively limited scale of alteration of spodumene (&lt;10 vol%) suggest that the activity of the hydrothermal fluids in the system is limited, which contributes to the preservation of the easily altered Li ores and is also an important controlling factor of the super-large-scale Li mineralization of the pegmatite. Spodumene–quartz intergrowth (SQI) usually occurs partly along the rims of the spodumene grains in the Jiajika No. 134 pegmatite. Combined with the pegmatite mineral equilibria, the results of fluid inclusion studies of the pegmatite and the metamorphic conditions in the area, a constrained P-T path of the magmatic–hydrothermal crystallization of the Jiajika No. 134 pegmatite is proposed. The unusual steeply sloped cooling path of the No. 134 pegmatite could be attributed to the fast pressure drop triggered by the intrusion of a pegmatitic melt along the fractures surrounding the Majingzi granite, which could also be the dominant evolution process for other spodumene pegmatites with similar SQI features in the world. The feature of limited internal geochemical fractionation suggested by mineral-scale geochemical analyses of spodumene and micas, combined with the clear textural zoning of the No. 134 pegmatite, can best be ascribed to the effect of undercooling during pegmatite formation. This effect might be one of the non-negligible rules of pegmatite petrogenesis, and would significantly upgrade the potential of Li mineralization by minimizing diffusional Li transfer to the country rocks.

Alkali element mobility as a vector for gold mineralization: An example from Central Brazil

The Brazilian Pilar and Três Buracos Paleoproterozoic mid-tier gold deposits are located in the south western Pilar de Goiás greenstone belt, containing 61,688 kg and 7,144 kg of gold, respectively, in addition to approximately 30,000 kg of past production (1736–2018). This research aimed to assess the hypothesis that the mobility of alkali elements may be used to facilitate the discovery of new gold deposits in hydrothermal systems by creating geochemical vectors based on alkali element mobility. The hypothesis was first proposed for the mafic rocks in the West Australian Goldfields and has been adopted in other deposits worldwide (E.g., Andorinhas greenstone belt, Brazil, Pataz gold field, Peru, and Rio das Velhas gold deposit, Brazil).The procedures consisted in the analysis of metasedimentary and mafic rock types from two drill holes from the Pilar de Goiás greenstone belt, central Brazil. These drill holes have intercepted mineralized and barren rock types. The petrographic and energy dispersive spectrometric results indicated that the host rocks around the orebodies present intense sericitization, albitization, and sulfidation. The chemical results reveal that the mobile elements Cs, Rb and Ba tend to be enriched in gold-bearing rock units and depleted in barren rock units. These elements are carried by fluids and can replace K in the structure of the newly formed hydrothermal phyllosilicates forming a halo of alkali-rich elements of up to 50 m around the orebodies.The upper continental crust normalized ratio ((Cs + Rb)/Th)UCC was adopted as an alteration index to evaluate and distinguish possible mineralized zones, with ((Cs + Rb)/Th)UCC > 3, from barren zones, with ((Cs + Rb)/Th)UCC < 3. The ratio ((Cs + Rb)/Th)UCC increases towards mineralization, providing a vector to possible gold mineralization, with a threshold value > 3 indicating high prospectivity.

Trace Metal Enrichments in Water of the Okavango Delta (Botswana): Hydrological Consequences

AbstractThe Okavango Delta in northern Botswana is an endorheic ecosystem formed by 150,000 islands surrounded by a flood plain. The vegetation of these islands displays an external tree ring enclosing a barren interior domain with evaporitic deposits. We sampled the groundwater into piezometers across an island at the southwest of the Delta, and drilled sediments. The geochemical analysis of the water exhibits two different compositions: a fresh water in the floodplain and a saline water in the interior part. These inner samples display enrichments in heavy metals, metalloids and critical metals such as, Rare Earth Elements (REE). The latest show a continuous enrichment from LREE to HREE and positive Ce and Eu anomalies, associated to alkaline pH. Overall, the two types of displayed REE patterns fingerprint two different water sources. The geochemistry of sediments indicates the same composition whatever the sample location and no traces of evaporitic deposits was found. The variations in the water table depth in the piezometers shows different hydrological behaviors in between the floodplain and the barren zone which does not follow the flood cycle. Thus, we document two different aquifers with independent hydrological behaviors: a surface fresh‐water aquifer in the floodplain connected to the channels, and a saline confined aquifer below the islands. The contrasted geochemical composition of the waters explains the distribution of the vegetation which survives through access to fresh water. The hydrological architecture of this island in the southwestern Delta differs from other islands, highlighting the hydrological complexity of the Okavango Delta.

Mineralogy of the Drazhnoye gold ore deposit, the Republic of Sakha (Yakutia)

New data on the mineral composition of the Drazhnoye gold deposit, located within the Taryn ore field, have been presented. The samples from the central and flank areas of the deposit, which characterize ore and barren zones, have been studied. Based on the detailed studies of the interrelationship and the form of mineral exhalations and their aggregates, the stages of mineral formation have been proposed, including two main stages: sediment-diagenetic and hydrothermal-metasomatic. It has been revealed that the main precipitator of early native gold was pyrrhotite, which later, with an increase in fugacity of sulfur, was almost replaced by later pyrite. At the end of hydrothermalmetasomatic stage, native gold is formed from gold-bearing solutions and is located often in quartz and quartzcarbonate veinlets as independent precipitates, less commonly associated with polymetallic minerals, pyrite and arsenopyrite. Previous researchers of the Drazhnoye deposit established its genetic relationship with hydrothermal solutions. The data obtained confirm this. According to the type of gold ore mineralization and the type of prospective deep source of solution, this field is previously attributed to a hydrothermal pluton-related gold — quartz formation.

Cold-seep fossil macrofaunal assemblages from Vestnesa Ridge, eastern Fram Strait, during the past 45 000 years

Four cores from Vestnesa Ridge on the western Svalbard margin from water depth of 1200 m have been studied. The Vestnesa Ridge is known for the presence of numerous pockmarks and active methane gas seepage is often observed in the form of acoustic gas flares. Three of the cores were collected from a pockmark with active seepage of methane and one core was taken just outside the seepage area for comparison. The cores show a range of influence from methane from no seepage (control core), moderate seepage, strong seepage to very strong seepage. All cores have been analyzed for the distribution of macrofossils, trace fossils, planktic foraminifera, stable isotopes, geochemistry and sedimentology. The main purpose of the study is to improve knowledge about the fossil macrofauna and past methane emissions in the area. The results show a major difference between the fauna recovered from cores taken inside a pockmark with chemosymbiotic bivalves and in some cases with a rich macrofauna&nbsp; and from the core recovered outside the pockmark that contained no macrofauna. The faunal relationships with the sedimentary environments confirm a close connection between the macrofauna and the presence/absence of cold-seepage, particularly seen in the occurrence of chemosymbiotic bivalves Archivesica arctica, Isorropodon nyeggaensis, potentially chemosymbiotic Rhacothyas kolgae and polychaetes. A barren zone in the core that was taken from the deepest part of the pockmark may indicate that a blow-out took place in the late glacial and the deglaciation into the early Holocene at c. 21,000–9000 years.

Benthic foraminifers as a proxy of the range of the tidal wave in the Oyambre Estuary (Cantabria, Spain)

Recent benthic foraminifers from the Oyambre estuary (north of Spain) have been studied in order to learn their biological response to drastic anthropic environmental changes that this estuary has undergone within the last centuries. Up to 41 species have been identified and 24 of them showed live specimens during the sampling period. The most abundant species are Ammonia tepida, Balticammina pseudomacrescens, Cribroelphidium williamsoni, Entzia macrescens, Haynesina germanica, Cibicidoides lobatulus, Miliammina fusca and Trochammina inflata. The statistical analysis (cluster and correspondence analysis) has allowed the differentiation of four groups of samples that are characterized by three assemblages that define the following environments: sandy outer estuary with marine influence (C. lobatulus), mid and inner estuary that comprises an euryhaline subtidal environment with silty sediment (A. tepida and H. germanica), intertidal channels with the lowest salinity levels (C. williamsoni), and marshes (B. pseudomacrescens, E. macrescens, M. fusca and T. inflata).The great number of species with agglutinated shells reveals the ongoing draining in mud-flat areas, as well as the establishment of the vegetated high marsh, where the invasive exotic plant Baccharis halimifolia is removing the reed bed ecosystem and filling, blocking and reducing main and secondary channels. As a result, there is hardly any sandy low marsh left, which in other nearby estuaries of Cantabria is delimited by the species M. fusca. Thus, areas with tidal levels between MHWNT (Mean High Water Neap Tide) and MHW (Mean High Waters) are scarce. However, foraminifer species that live in the high marsh above MHW are dominant. Entzia macrescens and T. inflata mark the interval between MHW and MHWST (Mean High Water Spring Tide), while B. pseudomacrescens the one from MHSWST to the barren zone (vegetated high marshes, closest to land).A comparison between the biocoenosis and thanatocoenosis assemblages generally shows a good similarity (Sanders’ index > 60%). The few samples with a low similarity reveal the effect of post-mortem processes, specially decantation, and, to a lesser extent, suspended transport, which once again points to the lack of hydrodynamism in the estuary. The percentage of exotic or allochthonous species that are deposited in this estuary is very low (the average ranges from 13.4% in the mouth to 0.7% in the inner area), which reveals that the Oyambre estuary has a mesotidal character in its mouth, while in the mid and inner area it can be considered a microtidal estuary. All these data expose that the works conducted in order to recover the Oyambre estuary between years 2009 and 2010 seem not to have been successful in restoring the marshes to their original hydrodynamic conditions.

Biostratigraphy and paleoenvironmental setting of the Lower Miocene succession at the west central Sinai, Egypt

Paleoenvironmental setting for the Lower Miocene successions exposed in a Wadi Gharandal can be interpreted using the integration of the lithologic characters and its foraminiferal association. Forty six agglutinated and seventy calcareous benthonic species has helped in segregate and distinguish six ecozones. Three transgressions (outer neritic to bathyal) and regressions (inner neritic and coastal) phases constitute three sedimentary cycles were recorded; the first transgression came with the deposition of the middle part of Mheiherrat Member; the second occurred during the deposition of the lower part of Hawara Member; while last one begins with the upper part of Asal Member. A great sea regression took place at the end of the Burdigalian forming an erosional surface, which represented by clastic sediments (sandstone lenses and pockets) and characterized by the absence of the microfaunal contents (foraminifera) followed by an anhydrite bed indicates a lagoonal environment for the lower part of Kareem Formation. The members of Rubies Formation are distinctively recognized and stratigraphically reconstructed based on its lithologic characters. Thirty-two planktonic foraminiferal species are also identified from the Aquitanian- Burdigalian successions that used to subdivide the studied rocks into three interval zoneszones (Globigerinoides primordius Zone; Globigerinoides altiaperturus Zone, Globigerinoides trilobus Zone) and one Barren Zone; these zones are correlated world wide with the standard international scheme of planktonic foraminiferal zoneszones and those recorded from neighboring areas.

Benthic Biotic Response to Climate Changes Over the Last 700,000 Years in a Deep Marginal Sea: Impacts of Deoxygenation and the Mid‐Brunhes Event

AbstractThe Sea of Japan is a marginal sea, connecting to adjacent seas by four shallow straits (water depths &lt;130 m). Marginal seas are ideal for studying biotic responses to large‐scale environmental changes as they often are sensitive to glacial‐interglacial and stadial‐interstadial climatic cycles. However, only a limited number of studies cover time periods beyond the last two glacial‐interglacial cycles. Here we present a 700,000‐year record of benthic biotic response to paleoceanographic changes in the southern Sea of Japan, covering the past seven glacial‐interglacial cycles, based on ostracode assemblages at the Integrated Ocean Drilling Program (IODP) Site U1427. The results indicate that long‐term oxygen variability in the bottom water has been the major control impacting the marginal‐sea biota. Five local extirpation events were recognized as barren zones during glacial maxima immediately before terminations I, II, IV, V, and VII, which are probably caused by bottom‐water deoxygenation. Results of multivariate analyses indicated clear faunal cyclicity influenced by glacial‐interglacial oxygen variability with a succession from opportunistic species dominance through tolerant infauna dominance to barren zone during the deoxygenation processes and the opposite succession during the recovery processes. The Sea of Japan ostracode faunal composition showed distinct difference between the post‐MBE and pre‐MBE (Mid‐Brunhes Event) periods, indicating the MBE as a major disturbance event in marginal‐sea ecosystems. The MBE shortened the duration of the extirpation events, fostered dominance of warmer‐water species, and amplified the glacial‐interglacial faunal cyclicity. Our long‐term biotic response study clearly indicates that deep marginal sea ecosystems are dynamic and vulnerable to climate changes.

Semi-isolated, flat-topped carbonate platform (Oligo-Miocene, Sardinia, Italy): Sedimentary architecture and processes

The Chattian-Aquitanian carbonate system of Isili sub-basin (SE Sardinia, Italy) were studied to better understand the hydrodynamic processes controlling the formation of landward-downlapping, rhodolith-rich, giant clinoforms.The studied flat-topped platform was attached to an island (semi-isolated) and migrated onshore (landward) over a shallow marine, protected embayment. The depositional profile is characterized by four, sea to land, zones: seaward slope, flat-topped platform (submerged flat), landward slope and mixed siliciclastic-carbonate embayment. In particular, these zones record different levels, from high to moderate, of hydrodynamic energy and persistency. The paleodepth of the studied succession, based on T/D test on Amphistegina specimens, red-algal genera and geometric reconstruction of the overall system, ranges from −10 to −30m for the platform up to around −40m for the landward slope base. Thus, the flat-topped platform was permanently submerged and an extensive carbonate (sea grass, algal and bryozoan-algal) factory along with oyster framestones developed. The widespread presence in the barren zones of rhodolith-to-shell rich small to very small compound dunes (high-energy zone) suggests that the flat-topped platform was periodically swept by unidirectional, landward-directed currents. These currents allow the formation of large-scale, rhodolith-rich clinobeds along the landward slope (washover fan-like system). The presence of rodolith pavements developed along the flat-topped platform at or slightly below the fairweather wave base suggests that clinobeds were formed in a nearshore, shallow subtidal setting. Finally, the shallow marine, protected embayment (moderate-energy zone) represents the widening distal reaches of the currents flowing or along the clinoforms or from the coast basinward (river floods and/or ebb tidal currents).Despite few tidal-related sedimentary structures such as bi-directional ripples and small compound dunes separated by finer-grained “drapes” or reactivation surfaces were observed, the prevailing processes acting over the platform are unidirectional, landward-directed currents possibly associated with longshore currents and/or wave actions. However, the resultant migration of the whole system onshore (landward) cannot be easily explained with storm or wind-related processes. Thus the studied flat-topped platform seems to be controlled by long term tidal regulation within a meso to macro tidal regime. In particular, such meso/macro tidal environments experience multiannual to multidecennial phases of stronger/weaker tidal range fluctuations resembling periods of relatively sea highs and lows with respect to the mean sea level (0m). All the (wind, storm, wave and tidal) currents sweeping the flat-topped platform were maxima during phases of strong tidal fluctuations generating erosion and sediment transportation over the flat and accumulation on the landward slope (clinobeds). Conversely, during phases of weaker tidal range fluctuations overall currents were minima, clinoforms did not develop and factories widespread re-colonized the submerged flat. Therefore, the studied platform developed in a current-dominated and tidal modulated setting.Finally, the studied carbonates of Sardinia suggest that the Sardinian seaway and the incipient Provençal basin during the Chattian-Aquitanian were, locally, capable to generate meso to macro tidal conditions.

Palaeoecology and distribution of upper Oligocene–lower Miocene foraminifera in the Qom Formation, the Bagher-Abad section, NE Isfahan, Central Iran

These palaeoecological investigations were carried out on foraminiferal assemblages from the Qom Formation in the Bagher-Abad section, northeast of Isfahan, Central Iran. Foraminiferal analysis of the lower limestone part of the succession revealed correlation with the Chattian zone SBZ (Shallow Benthic Zone) 23, and the overlaying marly strata revealed planktonic foraminifera of the Aquitanian Zone M1 (“Paragloborotalia” kugleri Taxon-range Zone). Finally, the topmost, barren zone, and benthic foraminifera assemblage were correlated with the Burdigalian, based on the regional stratigraphic scheme. Palaeoecological interpretations based on microfaunal composition and abundance of benthic foraminifera revealed that late Oligocene microfossils were dominated by larger foraminifera (Rotaliids), whereas early Miocene assemblage was dominated by miliolids. The foraminiferal associations generally reflect well-oxygenated shallow warm tropical waters within the photic zone (<50 m depth) during the Chattian–Burdigalian. These Oligocene/Miocene foraminiferal assemblages indicated middle shelf and inner shelf with normal marine salinity and oligotrophic-to-mesotrophic conditions.

The integration of physical rock properties, mineralogy and geochemistry for the exploration of large zinc silicate deposits: A case study of the Vazante zinc deposits, Minas Gerais, Brazil

The Vazante deposit, which is the world's largest zinc silicate deposit, occurs in brecciated dolomite and comprises mainly willemite with various proportions of hematite, Fe-carbonate, minor franklinite and magnetite. Exploration for this type of deposit is more challenging than zinc sulfide deposits, as they do not exhibit similar geophysical anomalies. To improve the application of geophysical surveys to the exploration of hypogene silicate zinc deposits, data from 475 samples were investigated from drill holes representative of the various types of ore and host rocks as well as barren zones of known geophysical anomalies in the Vazante District. Lithogeochemical and mineralogical (optical, SEM and MLA) data were integrated with physical rock properties (density, magnetic susceptibility and KUTh gamma-ray spectrometry) to assist in exploring for this type of deposit. The most distinct physical property of the ore is density, compared with the host rocks due to high proportion of denser minerals (hematite and willemite). However, barren hematite breccias also have high densities. The zinc ore and hematite breccias yielded higher magnetic susceptibilities than the surrounding host rocks, with the highest values associated with greater proportions of franklinite and magnetite. The density and magnetic susceptibility contrasts are a result of hydrothermal fluids interacting with and altering the carbonate host rocks. Zinc ore also yielded elevated U concentrations relative to the various host rocks, yielding higher gamma-ray spectrometric values. The results of this investigation indicate that an integration of magnetic, gravimetric and radiometric surveys would be required to identify zinc silicate ore zones.