Primary Rock Research Articles

Gondwana-derived units in Ograzhden and Belasitsa Mountains, Serbo-Macedonian Massif (SW Bulgaria): combined geochemical, petrological and U-Pb zircon-xenotime age constraints

The present study provides data on the high-grade metamorphic basement of the Serbo-Macedonian Massif (SMM) that is exposed in Ograzhden and Belasitsa Mountains, SW Bulgaria. We combined the conventional ID-TIMS with the in-situ LA-ICP-MS U-Pb zircon dating and compiled them with petrological and geochemical studies to better constrain the age and origin of the protoliths and the grade of metamorphic overprint. The orthogneisses are dated in the range of 450–455 Ma, except for the Kolarovo metagranites, which define two clusters of age data at 554.8 ± 3.3 Ma and 510.2 ± 3.5 Ma. We assume sedimentary origin for the plagiogneisses that show zircon population and age distribution similar to the gneiss-schists: main peak at ~600 Ma and minor populations at 700–800 Ma, 1000–1100 Ma and 2400 Ma. The amphibolites yield the youngest precursor ages of 435–440 Ma. The whole succession of rocks is metamorphosed to upper amphibolite facies conditions, with peak temperatures (Tmax) between 675–710 °C in Ograzhden Mountain and at ~650 °C in Belasitsa Mountain. Pressure estimates (Pmin) range from 6–8 kbar to 12–13 kbar, based on 3T phengite relics and application of different calibrations of phengite barometer. However, higher pressures cannot be excluded due to evidence from the eclogitic metabasites. The metamorphism has been dated in zircon rims of metasediments, vein rocks and amphibolites, as well as in xenotime of newly formed leucosome, at ~330 Ma. The wide range of primary rocks, their major- and trace-element chemistry and Sr-Nd isotope signature, combined with the age data of zircon populations, give evidence for an old crustal fragment with Gondwana affinity that was rejuvenated in the Ordovician–Silurian, before the collision and metamorphic overprint during the Variscan orogeny.

Selected Properties and Systematic Position of Soils Developed from Red Sandstones and Clays of the Lower Triassic Buntsandstein in the Nw Part of the Holy Cross Mountains (Poland) / Niektóre właściwości i pozycja systematyczna gleb wytworzonych z czerwonych piaskowców i iłów dolnego triasu w NW obrzeżeniu Gór Świętokrzyskich

AbstractThe aim of the study was to compare the properties of soils developed from the Lower Triassic Buntsandstein sediments in the north-western part of the Holy Cross Mountains (Poland). These are deposits of continental genesis and unique features such as red beds. Two representative soil pedons - the Bartków profile (pBK) developed from clay and the Góra Czerwona profile (pGC) developed from sandstone were selected for detailed analyzes. The morphology of profiles, their micromorphological features, mineralogical composition, and physico-chemical properties were examined. Most of the properties of the soils are a consequence of the original parent rock lithology. A specific feature of the morphology of the soils are the presence of red color (about 10R by the Munsell color scale) related to the presence of hematite. As shown by the XRD data, hematite is not the product of the current soil-forming processes, but it is a lithogenic component, which was inherited from the parent rock. Under the influence of climatic factors primary rock structure has been transformed into a new pedogenic one. Soils developed from clays have a characteristic angular blocky structure. Micromorphological analysis showed that an important role in the formation of soil structure involves geogenic susceptibility of Triassic clays to specific cuboid disintegration. This is indicated by the pore system of planes as an orthogonal nets visible in thin section. The soils developed from sandstone have a weak (unstable) subangular blocky structure. The main reason is the insufficient dispersion of the clay-ferruginous fraction from the sandstone matrix. Microscopic observations indicate that fine factions occurs as loose microaggregates, which results in a feature that smaller rock fragments and individual quartz grains are not bonded into soil aggregates. The studied soils are characterized by specific physical-chemical properties. Some of them strongly depend on the mineralogical properties of the soil substrate. Strong acidity (pH 3-4) and a very low content of base cations (below 1.0 cmol(+)kg-1) are due to a lack of carbonate minerals in sandstones and weak weathering of aluminium silicate. High exchangeable Al content in clay (16.5 cmol(+)kg-1) should be related to the geochemical properties of the red bed-type rocks such as the Lower Triassic Buntsandstein deposits. Soils developed from the Lower Triassic Buntsandstein clays have a sequence of genetic horizons: Ap, Bw, Bw/C, C and fulfill the criteria assigned to dystrophic typical brown soils (BDt) in the Polish Soil Classification (PSC 2011), whereas in the WRB they were classified as Endoeutric Chromic Cambisols (Loamic). Soils developed from the Lower Triassic Buntsandstein red sandstone can be classified as dystrophic humus brown soil (BDpr) in the PSC (2011). Within the WRB classification that soil can be assigned to Epidystric Chromic Endoleptic Cambisols.

LILE, REE, and HFSE partition coefficients between crystal and melt in migmatites of granulite facies of the Nimnyr block, Aldan shield

The behavior of Rb, Sr, Ba, Cr, V, Nb, Zr, REEs, and Y is studied in migmatites of granulite facies and the transitional zone to amphibolite facies in the western part of the Aldan granulite area. Our data allowed estimation of the partition coefficients of these elements in the crystal-melt system (Di) for orthopyroxene, garnet, clinopyroxene, and hornblende. The leucosomes of anatectic migmatites and diatectites (high-K charnockites and granites) were accepted as a melt, and the metapelites or previously granitized rocks (nebulites) and early leucosomes relative to late leucosome were the primary rocks and restite. The dependence of Di on the REE ionic radius is close to parabolic [7]. Our data allow identification of a qualitative link between the DiGrt/melt and the thermodynamic conditions of high-grade metamorphism and the accompanying partial melting, which leads to formation of a series of ultrametamorphic granitic rocks: lower temperature rocks (conditions of amphibolite facies) are characterized by higher DREE values relative to the zone of granulite facies. The late granitic rocks formed after diatectic charnockites are also characterized by higher DREE values relative to the preceding charnockites. For the conditions of granulite facies, the material belongs to rocks similar in the formation conditions; however, the series are strongly distinct in K content. The influence of the composition of the anatectic melt and acidity-alkalinity conditions on the partition coefficients of the studied elements is so strong that it eliminates the effect of temperature and pressure. The LREEs, Rb, Sr, and Ba will mostly accumulate in the garnet-orthopyroxene assemblage in the zone of melt origination, whereas HREEs will remain in restite along with Cr and V. Niobium and Zr may enrich the granitic melts. In contrast, the stability of amphibole in restite causes the depletion of melts in all REEs, Y, and Nb and enrichment in Rb, Sr, Ba, and, to a lesser extent, Zr.

Sand production assessment considering the reservoir geomechanics and water breakthrough

Sand production assessment is essential from the early stages of field development planning for completion design and later for the production optimisation. Unconsolidated and weakly consolidated sandstones are prone to fail at a low flowing bottomhole pressure during hydrocarbon production. To predict the critical flowing bottomhole pressure or a safe drawdown, a geomechanical model that integrates in situ stresses, rock mechanical properties, the well trajectory, reservoir pressure, the production plan and the depletion trend is required. For a given stress field, well trajectory and production plan, the rock strength index is a key parameter that has significant impacts on the sanding risk. This paper presents the results of a study investigating the potential of sand production from primary and secondary target reservoir rocks in a petroleum field in offshore Vietnam. A poroelastic analytical approach was used to investigate if sands will be produced from the open holes or perforations. The criterion of sanding was formulated to be the effective maximum principal stress to be greater than the effective rock strength. Observations of sanding or no sanding during drill stem tests (DSTs) were used to calibrate the sanding model to be used for sanding predictions of future production wells. The effects of reservoir pressure depletion on sanding risks were investigated using the stress arching theory. Since the water production from target reservoirs was observed in the nearby fields, the analysis was performed to investigate the effects of water production on rock weakening that may cause higher risks of sanding. The results showed low risks of sanding for majority of the reservoirs, with drawdowns as high as 3,000 psi at the original reservoir pressure. The drawdown was, however, required to reduce to 500 psi to produce sand-free after depleting the reservoir by more than 90% of its original pressure. The results of this study led to the decision of completing the wells without using sand control equipment and to avoid sanding by controlling drawdown for the life of the well.

Две серии первично-магматических пород в марун-кеуском эклогит-гнейсовом комплексе (Полярный Урал)

Две серии первично-магматических пород в марун-кеуском эклогит-гнейсовом комплексе (Полярный Урал)

Features of the Earth surface deformations in the Kamchatka peninsula and their relation to geoacoustic emission

Abstract. The paper presents the results of investigations of deformation processes in the near-surface sedimentary rocks, which have been carried out in a seismically active region of the Kamchatka peninsula since 2007. The peculiarity of the experiments on registration of geodeformations is the application of a laser strainmeter–interferometer constructed according to the Michelson interferometer scheme. Besides rock deformations, geoacoustic emission in the frequency range from several hertz to the first tens of kilohertz is under investigation. Piezoceramic hydrophones installed in artificial water reservoirs are applied. It is shown that periods of primary rock compression and tension with a duration of up to several months are distinguished in the geodeformation process at the observation site. During the direction change in the deformations, when the geodeformation process rate grows, an increase in geoacoustic radiation is observed.

Evaluation of structural and geological factors in orogenic gold type mineralisation in the Kervian area, north-west Iran, using airborne geophysical data

The Piranshahr-Sardasht-Saqqez Zone (PSSZ) in the north-west of the Sanandaj-Sirjan metamorphic zone (SSZ) hosts some major Iranian gold deposits. In the south-east of PSSZ, there is a north-east trending orogenic gold belt which contains three gold deposits/occurrences (Qolqoleh, Kervian and Ghabaghloujeh). In this research, studies are focused on processing and analysing airborne magnetic and radiometric data in order to find applicable indicators for prospecting gold in this area.Former studies on the gold deposits/occurrences in the study area suggest three essential factors in local orogenic gold mineralisation: (1) intersecting deep bending structures/shear zones, (2) Fe-rich mafic meta-volcanic lithologies (primary source and host rocks) and (3) altered mylonitic granites (secondary host rock). Geological structures and lithological contacts can be mapped based on locating edges in the magnetic field at different depths.In this study, we extracted the structure from aeromagnetic data by reduction to the pole, upward continuation and applying a tilt derivative filter to the horizontal derivative of the upward continued data. Upward continuation was to several levels from 500 to 4000 m. Afterwards, a 3D architecture was built based on extracted subsurface lineaments in different levels. This 3D model can assist in the visualisation of the underground shape of structures that may influence gold mineralisation.Moreover, mafic meta-volcanic rocks in the study area, which contain magnetic minerals such as magnetite, titanomagnetite and ilmenite, can be mapped using aeromagnetic data. Mylonitic granites, which are the other host rock in the deposits, were mapped using airborne radiometric data.

Mechanical and physical properties of hydrothermally altered rocks, Taupo Volcanic Zone, New Zealand

Mechanical characterization of hydrothermally altered rocks from geothermal reservoirs will lead to an improved understanding of rock mechanics in a geothermal environment. To characterize rock properties of the selected formations, we prepared samples from intact core for non-destructive (porosity, density and ultrasonic wave velocities) and destructive laboratory testing (uniaxial compressive strength). We characterised the hydrothermal alteration assemblage using optical mineralogy and existing petrography reports and showed that lithologies had a spread of secondary mineralisation that occurred across the smectite, argillic and propylitic alteration zones. The results from the three geothermal fields show a wide variety of physical rock properties. The testing results for the non-destructive testing shows that samples that originated from the shallow and low temperature section of the geothermal field had higher porosity (15 – 56%), lower density (1222 – 2114kg/m3) and slower ultrasonic waves (1925 – 3512m/s (vp) and 818 – 1980m/s (vs)), than the samples from a deeper and higher temperature section of the field (1.5 – 20%, 2072 – 2837kg/m3, 2639 – 4593m/s (vp) and 1476 – 2752m/s (vs), respectively). The shallow lithologies had uniaxial compressive strengths of 2 – 75MPa, and the deep lithologies had strengths of 16 – 211MPa. Typically samples of the same lithologies that originate from multiple wells across a field have variable rock properties because of the different alteration zones from which each sample originates. However, in addition to the alteration zones, the primary rock properties and burial depth of the samples also have an impact on the physical and mechanical properties of the rock. Where this data spread exists, we have been able to derive trends for this specific dataset and subsequently have gained an improved understanding of how hydrothermal alteration affects physical and mechanical properties.

Modular mobile foundation species as reservoirs of biodiversity

The complex structure of biogenic habitats including coral reefs, hemlock forests, and seagrass meadows are widely recognized for the diverse communities they shelter. As human impacts accelerate the loss of such foundation species, we need to identify the general characteristics of previously unrecognized species that can also fulfill the role of habitat provider. We conducted surveys and experiments to test whether the slate‐pencil urchin (Eucidaris galapagensis) acts as a foundation species on subtidal walls in the Galapagos archipelago. The spines of slate‐pencil urchins are more than 90% encrusted with a diverse epifauna, and a single urchin can host over 20 species (e.g., sponges, ascidians, bryozoans, corals, molluscs, worms, and crustaceans). Like many other foundation species, urchins can provide substrate and a refuge from predators. Urchins are consistently abundant throughout the Galapagos subtidal, and the total surface area of urchin spines can rival that of the primary rock substrate, which is significant since substrate availability can limit small‐scale species richness in this system. Our experimental manipulation of spine configuration and exclusion of predators revealed that urchins also enhance epifaunal diversity by providing a predation refuge. Unlike previously recognized foundation species, however, the urchin habitat is modular and mobile, and has the potential to redistribute associated epifauna. Characterizing how previously overlooked foundation species can act as reservoirs of biodiversity in ecosystems, such as the Galapagos where other foundation species such as coral have declined, has important implications for how we identify foundation species, predict ecosystem stability, and prioritize conservation efforts.

Отличительные черты гипергенного изменения пород различного состава

Comparative complex analysis of different types of weathering crust indicates that the following three factors along with mineralogical peculiarities of primary rocks and hydrogeochemical conditions are of great importance for formation of eluvial material. First factor is a degree of structural ordering of primary minerals. A second one is related to an inheritance of properties by new mineral phases. The third factor includes a universalism of processes of transformation of hypogene and formation of hypergene minerals in the weathering crusts developed in different types of rock. Realization of these basic assumptions can be achieved only with their integrated optical-electronic microscopy and structural-crystal-chemical investigations. This methodology allows distinguishing between the varieties of the same primary minerals using their structural specific features, as well as identifying secondary layered silicates formed at different stages of rocks hypergene alteration.

Conditions of accumulation of radioactive metals in the process of differentiation of ultrabasic alkaline-carbonatite rock associations

The distribution of radioactive elements in alkaline rocks from Polar Siberia and Ukraine shows that U and Th are markedly concentrated in carbonatite complex and nepheline syenite as final products of magma fractionation. Peralkaline nepheline syenites from Polar Siberia are characterized by very high contents of radioactive elements, which are close to the economic level. Radioactive elements are also concentrated in rocks of the carbonatite complex. For example, some soevites contain up to 294 × 10−4%U and 916 × 10−4% Th. In late dolomite carbonatites, the contents of radioactive elements are appreciably lower. The Th/U ratio in alkaline rocks of Polar Siberia is close to the chondrite value in primary high-Mg rocks and increases in late derivatives: phoscorite, calcite and dolomite carbonatites. The main amount of radioactive elements is contained in rare-metal accessory minerals: perovskite, pyrochlore, calzirtite, and apatite. Rock-forming minerals are distinguished by very low concentrations of radioactive elements. In alkaline series of the Chernigovka massif (Ukraine), U and Th also accumulate in the course of crystal fractionation, especially in phoscorites from the carbonatite complex. Mantle xenoliths and alkaline rocks from Ukraine reveal uranium specialization. Most likely, the discrepancy in fractionation of radioactive elements between Polar Siberia and Ukraine is caused by different geodynamic regimes of these provinces. The Mesozoic alkaline magmatism of Polar Siberia is a part of the Siberian superplume, whereas the Proterozoic alkaline complex in Ukraine is related to subduction of the oceanic crust.

Pore facies analysis: incorporation of rock properties into pore geometry based classes in a Permo-Triassic carbonate reservoir in the Persian Gulf

Pore facies analysis is a useful method for the classification of reservoir rocks according to pore geometry characteristics. The importance of this method is related to the dependence of the dynamic behaviour of the reservoir rock on the pore geometry. In this study, pore facies analysis was performed by the quantification and classification of the mercury injection capillary pressure (MICP) curves applying the multi-resolution graph-based clustering (MRGC) method. Each pore facies includes a limited variety of rock samples with different depositional fabrics and diagenetic histories, which are representative of one type of pore geometry. The present pore geometry is the result of the interaction between the primary rock fabric and its diagenetic overprint. Thus the variations in petrographic properties can be correlated with the pore geometry characteristics. Accordingly, the controlling parameters in the pore geometry characteristics were revealed by detailed petrographic analysis in each pore facies. The reservoir rock samples were then classified using the determined petrographic properties which control the pore system quality. This method is proposed for the classification of reservoir rocks in complicated carbonate reservoirs, in order to reduce the incompatibility of traditional facies analysis with pore system characteristics. The method is applicable where enough capillary pressure data is not available.

Геологічні пам’ятки як об’єкт рекреаційного природокористування на території НПП "Сколівські Бескиди"

Data about the objects of lifeless nature on the territory of the NNP "Skolivski Beskydy" are given. They can be used for organization of recreation activity. Interesting attractive objects for recreation and tourism are huge blocks of primary rocks (yamnenski sandstones) near Urych, Kryshelnytsya and Korchyn villages and landforms such as chunks. The places of extraction of minerals – an old quarry in the suburbs of Skole and in the tract Kolodka are considered In order to use for recreation. Using data from geological monuments of nature will lead to improvement of recreation in national parks. Key words: NPP, recreational activity, geological objects of nature.

Nature of co-bearing ferromanganese crusts of the Magellan Seamounts (Pacific Ocean): Communication 1. Geology, mineralogy, and geochemistry

Communication 1 of the present paper is devoted to various aspects of the hydrogenic ferromanganese crusts in the western and eastern clusters of the Magellan Seamounts in the Pacific. It was revealed that crusts are developed on guyots as a continuous sheet of Fe-Mn minerals on exposures of primary rocks. They commonly make up ring-shaped deposits along the periphery of the summit surface and in the upper sectors of slopes. Thickness of the crust varies from n to ∼18 cm and shows irregular variations in separate layers. Irrespective of the geographic position, crusts are composed of four layers—two lower phosphatized (I-1 and I-2) and two upper nonphosphatized (II and III) layers. The crusts differ in terms of structure and texture, but they are sufficiently similar within separate layers (I-1, I-2, and others). The major ore minerals in crusts are commonly represented by poorly crystallized and low-ordered minerals (Fe-vernadite and Mn-feroxyhyte); the subordinate mineral, by the well-crystallized and ordered vernadite. It has been established that heavy and rare metal cations are concentrated extremely irregularly in ore minerals of the crusts, suggesting a pulsating mode of their input during different geological epochs.

The geology and petrology of the metavolcanic rocks of the Kvakhona Formation of the Sredinnyi Range crystalline massif in Kamchatka

The metavolcanic rocks of the Kvakhona Formation exposed on the western slopes of the Sredinnyi Range metamorphic massif are represented by two sequences. The lower sequence occupying the most part of the exposed formation is dominated by porphyric and aphyric clinopyroxene-plagioclase metabasalts and their tuffs with subordinate metapicritic basalts, metaandesites and their tuffs, and metadacites. The latter form isolated bodies in the northern part of the Kvakhona exposures. The upper sequence is composed of metaandesites, metabasalts, and their tuffs intercalated with terrigenous rocks (siltstones, sandstones, and carbonate graywacke) and metadacite bodies. The rocks were subjected to intense metamorphism under the greenschist facies conditions (t = 250–420°C, P s around 1 kbar) with the replacement of clinopyroxene phenocrysts (or their clasts in the tuff varieties) by actinolite, chlorite, and epidote, while plagioclase phenocrysts are replaced by albite, muscovite, chlorite, and epidote. In the metabasalts enriched in ore minerals, clinopyroxene is replaced by very thin veinlets and the finest grains (about 20–30 μm) of Ca-Na and Na amphiboles (winchite, ferrowinchite, glaucophane, and ferroglaucophane). The groundmass of the rocks (or tuff cement) consists of variable combinations of titanite, magnetite, chlorite, epidote, silpnomelane, and albite. The metabasalts of the formation belong to the high-Fe and often high-Ti rocks, which makes them similar to the tholeiitic basalts of mid-ocean ridges or rifting zones. The metaandesites and metadacites also preserved an elevated Fe content and belong to calc-alkaline series rocks typical of island arcs and active continental margins. It is suggested that the primary rocks of the Kvakhona Formation were formed within volcanic centers on the floor of a vast Cretaceous epicontinental marginal basin, which accumulated thick sequences of terrigenous rocks. The detrital material for these rocks was supplied from the northeastern Asian continent. The geological and geochemical data testify to the similarity of the Kvakhona metavolcanic rocks and the greenstone altered volcanic rocks of the Pensantain Range of Western Kamchatka, which are dated by the U-Pb SHRIMP method at 90–100 Ma. The protolith of the metavolcanic rocks of the Kvakhona Formation was presumably formed within the same age interval.

Primary rock magnetism for the Wenchuan earthquake fault zone at Jiulong outcrop, Sichuan Province, China

Primary rock magnetism analysis was performed on samples from the Jiulong outcrop across the Anxian–Guanxian fault of the 2008 Wenchuan Earthquake rupture zone. The protolith of hanging wall of this outcrop is the upper Triassic sediments, which formed the fault breccia and gouge by repeated large earthquakes. The footwall of this outcrop contains Jurassic grayish-green and dark-purple sandstones. The average magnetic susceptibility value of the gouge is slightly less than that of potential protolith. Based on the primary rock magnetism, the main magnetic carriers are Fe-sulfides for the gouge, magnetite for the fault breccia, and magnetite and hematite for the Jurassic grayish-green and dark-purple sandstones. Possibly during or after repeated large earthquakes (just like the 2008 Mw 7.9 Wenchuan Earthquake), it transformed the magnetic mineral from magnetite to Fe-sulfides by low thermal decomposition processes along the Anxian–Guanxian earthquake fault, which induces the slightly less average magnetic susceptibility values of the gouge than that of potential protolith. If this magnetic mineral changed only because of repeated large earthquake process, the heating by low velocity seismic slip friction and seismic fluid could possibly have been less than 300 °C. If this magnetic mineral of the Anxian–Guanxian earthquake fault is only induced after repeated large earthquakes, the earth surface process acts an important role for the magnetic mineral change. More other further studies should be done to verify the primary magnetic mineral phase change and discriminate the time of this magnetic mineral variation.

Alteration minerals in impact-generated hydrothermal systems – Exploring host rock variability

Impact-generated hydrothermal systems have been previously linked to the alteration of Mars’ crust and the production of secondary mineral assemblages seen from orbit. The sensitivity of the resultant assemblages has not yet been evaluated as a function of precursor primary rock compositions. In this work, we use thermochemical modeling to explore the variety of minerals that could be produced by altering several known lithologies based on martian meteorite compositions. For a basaltic host rock lithology (Dhofar 378, Humphrey) the main alteration phases are feldspar, zeolite, pyroxene, chlorite, clay (nontronite, kaolinite), and hematite; for a lherzolithic host rock lithology (LEW 88516) the main alteration phases are amphibole, serpentine, chlorite, clay (nontronite, kaolinite), and hematite; and for an ultramafic host rock lithology (Chassigny) the main minerals are secondary olivine, serpentine, magnetite, quartz, and hematite. These assemblages and proportions of phases in each of those cases depend on W/R and temperature. Integrating geologic, hydrologic and alteration mineral evidence, we have developed a model to illustrate the distribution of alteration assemblages that occur in different levels of an impact structure. At the surface, hot, hydrous alteration affects the ejecta and melt sheet producing clay and chlorite. Deeper in the subsurface and depending on the permeability of the rock, a variety of minerals – smectite, chlorite, serpentine, amphiboles and hematite – are produced in a circulating hydrothermal system. These modeled mineral distributions should assist with interpretation of orbital observations and help guide surface exploration by rovers and sample return assets.

Dzhuluite, Ca3SbSnFe3+3O12, a new bitikleite-group garnet from the Upper Chegem Caldera, Northern Caucasus, Kabardino-Balkaria, Russia

Dzhuluite, Ca3SbSnFe3+3O12 ( Ia 3 d , a = 12.536(3) A, V = 1970.05(9) A 3, Z = 8), a new antimony garnet of the bitikleite-group, was discovered in a kumtyubeite zone in close proximity to the contact with unaltered ignimbrite in a skarn xenolith from the Upper Chegem Caldera, Northern Caucasus, Russia. The empirical formula of the holotype dzhuluite is (Ca2.954Fe2+0.043Mg0.003)∑3.000 (Sn0.850Sb5+0.764Zr0.121U6+0.127Ti4+0.070Sc0.009Nb5+0.058Hf0.001)∑2.001(Fe3+2.051Al0.653Fe2+0.182 Ti4+0.087Si0.028)∑3.001O12. Associated minerals are kumtyubeite, cuspidine, fluorchegemite, larnite, fluorite, wadalite, rondorfite, hydroxylellestadite, perovskite, lakargiite, kerimasite, elbrusite, srebrodolskite, bultfonteinite, ettringite group minerals, hillebrandite, afwillite, tobermorite-like minerals, hydrocalumite and hydrogrossular. Dzhuluite forms poikilitic crystals <50 μm in size that are light-yellow to dark-brown and with a creamy streak. The lustre is strongly vitreous. The calculated density of dzhuluite ranges from 4.708 to 4.750 g/cm3. Raman spectra are analogous to those of kimzeyite, kerimasite and other bitikleite-group minerals. Dzhuluite formed at high temperature during a retrograde stage of primary rock alteration in the larnite subfacies (sanidinite facies) as a result of fluorine metasomatism.

A Comparative Analysis of Evaporate Sediments on Earth and Mars: Implications for the Climate Change on Mars

Abstract:The knowledge of Martian salts has gone through substantial changes during the past decades. In the 70th of last century, Viking landers have noticed the existence of salts on Mars. Several salt species have been suggested from then on, such as sulfates and chlorides. However, their origin was a mystery due to the lack of observations. The recent explorations and related studies at the beginning of this century revealed that the crustal composition of Mars is similar to that of Earth, and it was hypothesized that almost one third of Martian surface was covered by oceans and lakes in the early stage of Mars. The huge water bodies may have dissolved a large quantity of ions from Martian primary rocks during the whole Noachian and Hesperian epoch. After the enormous drought event happened during the late Hesperian and the early Amazonian, these dissolved ions have formed huge salts deposits and most of them were preserved on Mars until today. To date, carbonates, sulfates, chlorides have all been detected by orbital remote sensing and by landers and rovers. However, the salt mineral assemblages on Mars seems to have some differences from those on Earth, e.g., rich in sulfates and lack of massive carbonates. To explain this difference, we propose that most of the surface carbonates precipitated from the ancient oceans may have been dissolved by the later ubiquitous acidic fluids originated from the global volcanism in the Hesperian era, and formed the enormous sulfate deposits as detected, and this hypothesis seems to be supported by the evidence that most of the sulfate deposits distribute around the Tharsis volcanic province while the survived carbonates located far from it. This process can release most of the carbon on Mars to the atmosphere in the form of CO2 and then be erased by the late heavy bombardments, which might have profound influence on the climate change happened in the Hesperian age. The positive correlation between the GRS results of the potassium distributions and the distribution of chlorides on Mars, together with the high Br concentration measured from the evaporate sediments at two Mars exploration rover landing sites, indicate that the brines in the regions where the chlorides deposited may have reached the stage for potassium salts deposition, thus we propose for the first time that potassium salts deposits might be prevalent in these regions.

Does temperature or runoff control the feedback between chemical denudation and climate? Insights from NE Iceland

The relative role of temperature and runoff on the chemical denudation rates in seven NE Iceland river catchments were determined through the analysis of river water chemistry collected over a five-year period. Denudation rates are quantified from the instantaneous riverine Na fluxes. As sodium is the major element least incorporated into secondary phases, its denudation rate is directly related to the dissolution rate of the catchments’ primary rocks. Chemical transport in rivers is taken to be analogous to laboratory mixed-flow reactors; dissolution rates in mixed flow-reactors at fixed temperature and flow rate are a function of fluid composition, degree of fluid undersaturation, the Arrhenius activation energy, and reactive surface area. Data analysis suggests that the Na chemical denudation rates of the NE Icelandic catchment rocks increase by 13% for each °C increase in temperature. Of this 13%, 5% stems from the Arrhenius activation energy and 8% stems from the temperature dependence of the fluid pH and aqueous Al activity. Increased runoff raises the height of the water table thus enhancing chemical denudation by increasing the reactive surface area of weathering minerals. Regression of measured Na fluxes indicate that the average active water–rock surface area of the studied catchments increase linearly with runoff such that a 1% rise in runoff produces a 1% increase in reactive surface area and chemical denudation rates. The relative role of temperature versus runoff on chemical denudation depends, therefore, on the relative changes in these two rate controlling parameters. The maximum temperature variation of the studied rivers was 15.4°C, which would increase Na chemical denudation rates by a factor of 6. In contrast, instantaneous runoff varies by as much as a factor of 250. These observations suggest that runoff dominates the instantaneous variation of the Na chemical denudation rates of the studied catchments.