Zincobotryogen and zincocopiapite–two new varieties of sulfate minerals

Two new varieties of sulfate minerals, zincobotryogen and zincocopiapite, belonging to the botryogen group and the copiapite group, respectively, were found in the oxidation zone of a lead-zinc deposit, situated on the northern border of the extremely arid Tsadam basin. – Authors.     

Scale,causality, and the new organism–environment interaction

The fallout from environmental determinism of the early 20th century steered geography away from biological and evolutionary thought. Yet it also set in motion the diversification of how geographers conceive environment, how these environments shape and are shaped by humans, and how scaling negotiates the interpretation of this causality. I illustrate how this plurality of scalar perspectives and practices in geography is embedded in the organism–environment interaction recently articulated in the life sciences. I describe the new fields of epigenetics and niche construction to communicate how ideas about scale from human and physical geography come together in the life sciences. I argue that the two subdisciplinary modes or ‘moments’ of scalar thinking in geography are compatible, even necessary, through their embodiment in organisms. To procure predictability, organisms practice an epistemological scaling to rework the mental and material boundaries and scales in their environment. Yet organisms are also embedded in ontological flux. Boundaries and scales do not remain static because of the agency of other organisms to shape their own predictability. I formally define biological scaling as arising from the interplay of epistemological and ontological moments of scale. This third moment of scale creates local assemblages or topologies with a propensity for persistence. These ‘lumpy’ material outcomes of the new organism–environment interaction have analogues in posthuman and new materialist geographies. They also give formerly discredited Lamarckian modes of inheritance a renewed, but revised acceptance. This article argues for a biological view of scale and causality in geography.     

`Crack–seal', slip: a new fault valve mechanism?

This paper presents a new model of fault development in carbonate rocks involving a crack–seal–slip sequence. The structures of sheared calcite veins from the Les Matelles outcrop, Languedoc (S. France), and the observations used to construct this new model which integrates aspects of `crack–seal' evolution of calcite-filled veins with concepts of fault valve behaviour are described. In our model, hydraulic mode I reopening of an oblique pre-existing vein in an overall strike-slip stress regime is accompanied by precipitation of calcite, but significant fault slip cannot occur initially despite this obliquity because the ends of the pre-existing structure limit further reopening propagation beyond the tips. The rate of aligned calcite precipitation keeps pace with the rate of dilation of the structure, so that calcite cement essentially seals the system. Stress concentrations at the tips are allowed to rise with reopening until failure of the tip zone results in branch crack formation, triggering both slip along the vein and hydraulic pressure drop. This is followed by sealing within the branch cracks. Such a crack–seal–slip cycle may be repeated several times, as evidenced by fault-perpendicular calcite vein growth interlayered with calc-mylonite lamellae within these structures. Later cycles will become less pronounced because strength recovery of the sealed branch cracks does not regain the initial strength of the intact rock. This model could apply at various scales, and could be a mechanism for triggering earthquakes.     

Some new data on the genesis of the Linghou Cu–Pb–Zn polymetallic deposit—Based on the study of fluid inclusions and C–H–O–S–Pb isotopes

The Linghou deposit, located near Hangzhou City of Zhejiang Province, eastern China, is a medium-sized polymetallic sulfide deposit associated with granitic intrusion. This deposit is structurally and lithologically controlled and commonly characterized by ore veins or irregular ore lenses. In this deposit, two mineralization events were identified, of which the former produced the Cu–Au–Ag orebodies, while the latter formed Pb–Zn–Cu orebodies. Silicification and calc-silicate (skarn type), phyllic, and carbonate alternation are four principal types of hydrothermal alteration. The early Cu–Au–Ag and late Pb–Zn–Cu mineralizations are characterized by quartz ± sericite + pyrite + chalcopyrite + bornite ± Au–Ag minerals ± magnetite ± molybdenite and calcite + dolomite + sphalerite + pyrite + chalcopyrite + galena, respectively. Calcite clusters and calcite ± quartz vein are formed during the late hydrothermal stage.The NaCl–H₂O–CO₂ system fluid, coexisting with NaCl–H₂O system fluid and showing the similar homogenization temperatures (385 °C and 356 °C, respectively) and different salinities (16.89–21.68 wt.% NaCl eqv. and 7.70–15.53 wt.% NaCl eqv.), suggests that fluid immiscibility occurred during the Cu–Au–Ag mineralization stage and might have given rise to the ore-metal precipitation. The ore-forming fluid of the Pb–Zn–Cu mineralization mainly belongs to the NaCl–H₂O–CO₂ system of high temperature (~ 401 °C) and mid-high salinity (10.79 wt.% NaCl eqv.).Fluids trapped in the quartz-chalcopyrite vein, Cu–Au–Ag ores, Pb–Zn–Cu ores and calcite clusters yielded δ¹⁸O_H2O and δD values varying from 5.54‰ to 13.11‰ and from − 71.8‰ to − 105.1‰, respectively, indicating that magmatic fluids may have played an important role in two mineralization events. The δ¹³C_PDB values of the calcite change from − 2.78‰ to − 4.63‰, indicating that the CO₃^2 − or CO₂ in the ore-forming fluid of the Pb–Zn–Cu mineralization was mainly sourced from the magmatic system, although dissolution of minor marine carbonate may have also occurred during the ore-forming processes. The sulfide minerals have homogeneous lead isotopic compositions with ²⁰⁶Pb/²⁰⁴Pb ranging from 17.958 to 18.587, ²⁰⁷Pb/²⁰⁴Pb ranging from 15.549 to 15.701, and ²⁰⁸Pb/²⁰⁴Pb ranging from 37.976 to 39.052, indicating that metallic elements of the Linghou deposit came from a mixed source involving mantle and crustal components.Based on geological evidence, fluid inclusions, and H–O–C–S–Pb isotopic data, the Linghou polymetallic deposit is interpreted as a high-temperature, skarn-carbonate replacement type. Two types of mineralization are both related to the magmatic–hydrothermal system, with the Cu–Au–Ag mineralization having a close relationship with granodiorite.     

A new approach in assessing recharge of highly karstified terrains–Montenegro case studies

The recharge of a karst aquifer, in terms of its quantity and spatial distribution, depends on various natural factors such as climate, topography, vegetation, soil, and geology. Selection of an adequate method for assessing recharge in karst is often a matter of dispute. Multi-parameter methods using Geographical information systems tools have recently been successfully developed and applied in karstic terrains of Spain and Lebanon. Specific local conditions such as highly karstified terrains could additionally complicate such an assessment. The Montenegro karstified terrains in the southern part of the External Dinarides are characterized by a very high precipitation rate, irregular seasonal distribution, and absence of surface waters (extremely high infiltration capacity of karst). Considering such conditions, an attempt to apply existing knowledge and experiences to the development of an appropriate multi-parameter method for assessing spatial distribution of autogenous recharge has been made. The KARSTLOP method has been developed, applied, and calibrated at catchments of several large karst springs of Montenegro. Obtained results in tested catchment areas confirm that with some further improvements the KARSTLOP method could be a useful tool to support research of karstic aquifers in similar highly karstified terrains.     

The masquerade of alkaline–carbonatitic tuffs by zeolites: a new global pathfinder hypothesis

Rapid and progressive reaction of alkaline–carbonatitic tuffs with magmatic and crustal fluids disguises their initial character and origin. This is collectively indicated from (a) the extensive literature on zeolite formation from volcanic glass precursors and alkaline fluids, (b) mineralogical characteristics of specific zeolite species, (c) a comparative review of global distributions of alkaline–carbonatite suites and of zeolite minerals, and (d) new trace element data from zeolite samples. A unifying conceptual model based on tectonic and geological settings, hydrological regime and mineralogy is presented that helps to explain the global distributions and current understanding of occurrences. The model will assist in resource exploration by contributing deeper understanding of the economically important bedded zeolite deposits and further, serve as a guide to the discovery of new alkaline–carbonatitic suites, potentially of economic significance (metallic ores and rare earth elements). It follows that future testing of the hypothesis will impact on models of natural carbon cycling as volcanic contributions of CO₂ are reviewed.     

In situ Lu–Hf phosphate geochronology: Progress towards a new tool for space exploration

Geochronology is fundamental to understanding planetary evolution. However, as space exploration continues to expand, traditional dating methods, involving complex laboratory processes, are generally not realistic for unmanned space applications. Campaign-style planetary exploration missions require dating methods that can (1) rapidly resolve age information on small samples, (2) be applied to minerals common in mafic rocks, and (3) be based on technologies that could be installed on future rover systems. We demonstrate the application of rapid in situ microanalytical Lu–Hf phosphate geochronology using samples of pallasite meteorites, which are representative examples of the deep interiors of differentiated planetoids that are generally difficult to date. Individual pallasites were dated by laser ablation tandem mass-spectrometry (LA-ICP-MS/MS), demonstrating a rapid novel method for exploring planetary evolution. Derived formation ages for individual pallasites agree with traditional methods and have <2% uncertainty, opening an avenue of opportunity for remote micro-analytical space exploration.     

Jurassic volcaniclastic – basaltic andesite – dolerite sequence in Tasmania: new age constraints for fossil plants from Lune River

Jurassic plants excavated from a 12 × 5 m site, at Lune River, southern Tasmania, include an araucarian tree and numerous pteridophytes, belonging to the orders Osmundales, Filicales and Bennettitales. The fossils occur in 2 – 3 m of immature volcanilithic sandstone beds. The sandstone consists primarily of clasts from granitic basement rocks underlying much of southeast Tasmania and mafic clasts containing feldspathic microliths, and primary, phreatomagmatic quartz crystals. Detrital zircons from the sandstones are mostly Early Jurassic (Toarcian) in age (182 ± 4 Ma) with minor Triassic (226 Ma), Devonian (380 – 360 Ma) and Proterozoic populations. Basaltic andesite, hereafter referred to as andesite, caps the volcanilithic units and displays similar ratios of fluid-immobile trace elements (e.g. Zr/Nb, Ti/V), to the Jurassic dolerite found in Tasmania, indicative of a common source. The andesites are correlated with the Jurassic Kirkpatrick Basalts (Trans-Antarctic Mountains, Antarctica) based on their field relationships with bounding strata, age, and distinctive similarities in major-element composition and fluid-immobile trace-element ratios. The andesite is interpreted as an extrusive equivalent of the Tasmanian dolerite. Importantly, drillcore from Lune River contains stoped clasts of andesite in fine-grained dolerite, indicating that the andesite pre-dates the dolerite. Thermal alteration index of microfossils (3 – 3.3) and reflectance of organic material within the sediments (0.54 – 0.77 Ro) resulted from contact metamorphism associated with the emplacement of this basalt. The sedimentology and stratigraphy of the depositional environment, plus the presence of hydrophilic pteridophytes and gymnosperms, indicates that the Toarcian environment was temperate to warm and humid, with an abundant supply of water.     

Petrogenetic and metallogenetic responses to Miocene slab flattening: new constraints from the El Indio-Pascua Au–Ag–Cu belt,Chile/Argentina

The Eocene–Miocene volcanic and hypabyssal rocks of the El Indio-Pascua Au–Ag–-Cu belt in the southern central Andean flat-slab region are medium–high-K calc-alkaline arc suites, ranging in composition from andesite to rhyolite. A significant transition in magmatic trace element chemistry, coinciding with a pronounced reduction in magma output, occurred in the late-Middle Miocene as documented by ⁴⁰Ar–³⁹Ar geochronology. The upper Eocene–lower-Middle Miocene rocks exhibit low Sr/Y ratios (<50), minor heavy REE fractionation with Sm/Yb ratios not exceeding 3.5 and, in some cases, minor negative Eu anomalies. In contrast, the largely dacitic rocks erupted after ca. 13 Ma are depleted in Y (10 ppm), have generally high, but variable Sr/Y ratios (30–200), exhibit moderate middle and heavy REE fractionation (Sm/Yb: 3.7–5.9) and lack negative Eu anomalies. The latter features are characteristic of adakitic suites (i.e. slab-melts), but the regional temporal and spatial distribution of arc magmatism precludes a major magma source in the downgoing slab. This evolution is interpreted as reflecting a progressive increase in pressure and the availability of water in the lower-crustal site of magma generation, establishing both garnet and hornblende as major stable phases in the residuum. The pressure in the lower crust increased in response to episodic crustal thickening related to the shallowing of the slab, a process recorded by the incision of three regional pediplains over the period 17–6 Ma. Elimination of the subarc asthenospheric mantle and much of the lithospheric mantle by ca. 10 Ma permitted direct incursion of slab-derived, highly oxidised metal- and volatile-rich supercritical fluids into the lower crust, stimulating melting of mafic, garnet amphibolitic and eclogitic assemblages.The igneous suites emplaced from 36–11 Ma were associated with widespread, and locally intense, epizonal hydrothermal activity, but this was barren of base and precious metals. The shallow-crustal availability of abundant water highlighted in earlier models was therefore not a metallogenetic determinant. Moreover, economic Au–Ag–Cu mineralization, associated with small volumes of dacitic magma, was restricted to the interval 9.5–5 Ma, and was not initiated until at least 3.5 my after the inception of high-pressure magma generation. In contrast to previous metallogenetic studies, we therefore suggest that this petrochemical transition was not inherently favourable for ore formation. We propose that the incursion of highly oxidized supercritical fluids from the slab into the lower crust was ultimately responsible for the brief Late Miocene metallogenetic episode.Electronic Supplementary Material Supplementary material is available in the online version of this article at Editorial handling: V. Bouchot     

A new U–Pb zircon age and a volcanogenic model for the early Permian Chemnitz Fossil Forest

International Journal of Earth Sciences - The Chemnitz Fossil Forest depicts one of the most completely preserved forest ecosystems in late Paleozoic Northern Hemisphere of tropical Pangaea. Fossil...     

Meso–Neoarchaean crustal evolution of the Bundelkhand Craton,Indian Shield: new data from greenstone belts

ABSTRACT

The Mauranipur and Babina greenstone belts of the Bundelkhand Craton are formed of the Central Bundelkhand greenstone complex (CBGC). This complex represents tectonic collage which has not been previously studied in depth. The purpose of this study is to contribute to the understanding of the main features of the Archaean crustal evolution of the Bundelkhand Craton. The CBGC consists of two assemblages: (1) the early assemblage, which is composed of basic-ultramafic, rhyolitic–dacitic, and banded iron formation units, and (2) the late assemblage, which is a felsic volcanic unit. The units and assemblages are tectonically unified with epidote–quartz–plagioclase metasomatic rocks formed locally in these tectonic zones.

The early assemblage of the Mauranipur greenstone belt is estimated at 2810 ± 13 Ma, from the U–Pb dating (SHRIMP, zircon) of the felsic volcanics. Also, there are inherited 3242 ± 65 Ma zircons in this rock. It is deduced that this assemblage is related to early felsic subduction volcanism during the Mesoarchaean that occurred in the Bundelkhand Craton.

Zircons extracted from metasomatic rocks in the early assemblage’s high-Mg basalts show a concordant age of 2687 ± 11 Ma. This age is interpreted as a time of metamorphism that occurred simultaneously with an early accretion stage in the evolution of the Mauranipur greenstone belt.

The felsic volcanism, appearing as subvolcanic bodies in the late assemblage of the Mauranipur greenstone belt, is estimated to be 2557 ± 33 Ma from the U–Pb dating (SHRIMP, zircon) of the felsic volcanic rocks. This rock also contains inherited 2864 ± 46 Ma zircons. The late assemblage of the Mauranipur greenstone belt corresponds with a geodynamic setting of active subduction along the continental margin during Neoarchaean.

The late assemblage Neoarchaean felsic volcanic rocks from the Mauranipur and Babina greenstone belts are comparable in age and geochemical characteristics. The Neoarchaean rocks are more enriched in Sr and Ba and are more depleted in Cr and Ni than the Mesoarchaean felsic volcanic rocks of the early assemblage.

Through isotopic dating and the geochemical analysis of the volcanic and metasomatic rocks of the CBGC, this study has revealed two subduction–accretion events, the Meso–Neoarchaean (2.81–2.7 Ga) and Neoarchaean (2.56–2.53 Ga), during the crustal evolution of the Bundelkhand Craton (Indian Shield).     

A new high-stress undrained ring-shear apparatus and its application to the 1792 Unzen–Mayuyama megaslide in Japan

Sassa and others in the Disaster Prevention Research Institute (DPRI), Kyoto University, developed a series of undrained ring-shear apparatus to physically simulate landslide initiation and motion, from DPRI-3 (Sassa 1992) to DPRI-7 (Sassa et al., Landslides 1(1):7–19, 2004). The maximum undrained capacities in the DPRI series ranged from 300 to 650 kPa. Sassa and others in the International Consortium on Landslides (ICL) have developed a new series of undrained ring-shear apparatus (ICL-1and ICL-2) for two projects of the International Programme on Landslides (IPL-161 and IPL-175). Both projects are supported by the Science and Technology Research Partnership for Sustainable Development Program (SATREPS) of Japan. ICL-1 was developed to create a compact and transportable apparatus for practical use in Croatia; one set was donated to Croatia in 2012. ICL-2 was developed in 2012–2013 to simulate the initiation and motion of megaslides of more than 100 m in thickness. The successful undrained capacity of ICL-2 is 3 MPa. This apparatus was applied to simulate possible conditions for the initiation and motion of the 1792 Unzen–Mayuyama megaslide (volume, 3.4?×?10⁸ m³; maximum depth, 400 m) triggered by an earthquake. The megaslide and resulting tsunami killed about 15,000 people. The Unzen Restoration Office of the Ministry of Land, Infrastructure and Transport (MLIT) of Japan systematically collected various papers and reports and published two summary leaflets: one in English in 2002 and an extended version in Japanese in 2003. Samples were taken from the source area (for initiation) and the moving area (for motion). The hazard area was estimated by the integrated landslide simulation model LS-RAPID, using parameters obtained with the ICL-2 undrained ring-shear apparatus. The estimated hazard area agrees reasonably with the landslide moving area reported in the Ministry leaflets.     

The Wadi Zaghra metasediments of Sinai,Egypt: new constraints on the late Cryogenian–Ediacaran tectonic evolution of the northernmost Arabian–Nubian Shield

ABSTRACT

The La Tinta mélange is a small but singular ultramafic mélange sheet that crops out in eastern Cuba. It is composed of dolerite-derived amphibolite blocks embedded in a serpentinite matrix. The amphibolite blocks have mid-ocean ridge basalt (MORB)-like composition showing little if any imprint of subduction zone component, similar to most forearc and MOR basalts worldwide. Relict Cr-spinel and olivine mineral chemistry of the serpentinized ultramafic matrix suggest a forearc position for these rocks. These characteristics, together with a hornblende ⁴⁰Ar/³⁹Ar age of 123.2 ± 2.2 Ma from one of the amphibolite blocks, suggest that the protoliths of the amphibolite blocks correspond to forearc basalt (FAB)-related rocks that formed during the earlier stage of subduction initiation of the Early Cretaceous Caribbean arc. We propose that the La Tinta amphibolites correspond to fragments of sills and dikes of hypoabyssal rocks formed in the earlier stages of a subduction initiation scenario in the Pacific realm (ca. 136 Ma). The forearc dolerite-derived amphibolites formed by partial melting of upwelling fertile asthenosphere at the beginning of subduction of the Proto-Caribbean (Atlantic) slab, with no interaction with slab-derived fluids/melts. This magmatic episode probably correlates with Early Cretaceous basic rocks described in Hispaniola (Gaspar Hernandez serpentinized peridotite-tectonite). The dikes and sills cooled and metamorphosed due to hydration at low pressure (ca. 3.8 kbar) and medium to high temperature (up to 720ºC) and reached ca. 500ºC at ca. 123 Ma. At this cooling stage, serpentinite formed after hydration of the ultramafic upper mantle. This process might have been favoured by faulting during extension of the forearc, indicating an early stage of dike and sill fragmentation and serpentinite mélanges formation; however, full development of the mélange likely took place during tectonic emplacement (obduction) onto the thrust belt of eastern Cuba during the latest Cretaceous.     

Ammonoid discoveries in the Antimonio Formation,Sonora, Mexico: new constraints on the Triassic–Jurassic boundary

The Triassic–Jurassic systemic boundary was recently reported in the middle part of the Antimonio Formation, northwestern Sonora, where five informal sedimentary packages were delineated and characteristic ammonoid faunas were used to establish age control within the succession. The boundary was suggested to lie within the middle part of the 24 m-thick package 4, in relatively unfossiliferous and organic-rich, laminated clay-silt mudstone. Despite the absence of diagnostic Hettangian fossils above the postulated boundary interval, its existence was predicted on characteristic uppermost Triassic Crickmayi Zone Choristoceras ammonoids occurring below in package 3 and upper Hettangian to lower Sinemurian (Badouxia Zone) ammonoids found above in package 5. Recent field investigations yielded new ammonoids of the uppermost Triassic Crickmayi Zone, which are described herein. They are assigned to Choristoceras cf. C. nobile Mojsisovics and Rhabdoceras cf. R. suessi Hauer. These characteristic ammonoids occur within the middle and top of package 4. Their discovery along with other stratigraphic evidence necessitates a revision of the boundary and recognition of a previously unrealized unconformity at the Triassic–Jurassic boundary in Sonora. A revised sea-level curve is necessary to account for these new stratigraphic and paleontological findings.     

A new generalized soil thermal conductivity model for sand–kaolin clay mixtures using thermo-time domain reflectometry probe test

As the demand of exploitation and utilization of geothermal energy increases, more geothermal-related earth structures occur recently. The design of the structures depends upon an accurate prediction of soil thermal conductivity. The existing soil thermal conductivity models were mostly developed by empirical fits to datasets of soil thermal conductivity measurements. Due to the gaps in measured thermal conductivities between any two tested natural soils, the models may not provide accurate prediction for other soils, and the predicted thermal conductivity might not be continuous over the entire range of soil type. In this research, a generalized soil thermal conductivity model was proposed based on a series of laboratory experiments on sand, kaolin clay and sand–kaolin clay mixtures using a newly designed thermo-time domain reflectometry probe. The model was then validated with respect to k _dry–n (thermal conductivity of dry soils and porosity) and k _r–S _r (normalized thermal conductivity and degree of saturation) relationships by comparing with previous experimental studies. The predicted thermal conductivities were found to be in a good agreement with the experimental data collected from both this study and the other literatures with at least 85% confidence interval. It is concluded that the proposed model accounts for the effects of both environmental factors (i.e., moisture content and dry density) and compositional factors (i.e., quartz content and soil type) on soil thermal conductivity, and it has a great potential in predicting soil thermal conductivity more accurately for geothermal applications.