Mica Minerals Research Articles

Mineralogical characterization of Greda clays and monitoring of their phase transformations on thermal treatment

The mineralogical characterization of two clay samples from the Central Andean Region of Peru, denominated White Greda and Red Greda, is reported. These clays contain the clay minerals mica and illite respectively. Both clays were treated thermally in an oxidising atmosphere under controlled conditions up to 1,100°C with the purpose of obtaining information about structural changes that may be useful for pottery manufacture. X-ray fluorescence was used for the elemental characterization of the samples and X-ray diffractometry was used to determine the collapse and formation of the mineral phases present in the samples caused by thermal treatment. At temperatures above 1,000°C it is observed the formation of spinel in the case of White Greda and of hematite, corundum and cristobalite in the case of Red Greda. Room temperature transmission Mossbauer spectroscopy allowed the monitoring of the variation of the hyperfine parameters with the thermal treatment temperature; In the case of the evolution of the quadruple splitting of the paramagnetic Fe3 + sites with temperature, in both clays, the analyses reproduced results such as the “camel back” curve shape, found by other workers (Wagner and Wagner, Hyperfine Interact 154:35–82, 2004; Wagner and Kyek, Hyperfine Interact 154:5–33, 2004).

Early Proterozoic diamond-bearing kimberlites of Karelia and their formation peculiarities

Early Proterozoic kimberlites of Karelia are among the most ancient diamond-bearing primary source rocks in the world. They compose the large (2.0 × 0.8 km) Kimozero body localized in the predicted Zaonezhskoe kimberlite field. The established and assumed occurrences of kimberlite magmatism are located within the Karelian craton, which was stabilized during the Early Archean. They are confined to the central part of a large geophysical anomaly detected by gravity, magnetic, seismic, and heat-flow studies and mark a deep-seated magma chamber. Kimberlite bodies occur within structural blocks bounded by zones of plicative-rupture dislocations. The Kimozero kimberlites form an extensive but thin saucer-like body cut by narrow quasi-cylindrical feeders and dikes. It consists of metamorphosed kimberlites, their breccias and tuffs with widely varying amounts of mica. The body includes fragmentary fine-layered crater formations. The rocks contain olivine and phlogopite phenocrysts in an extremely altered groundmass of serpentine, chlorite, calcite, mica, and ore minerals as well as indicator minerals of kimberlites, such as Cr-spinel, manganiferous ilmenite, Cr-diopside, and rare pyrope. About 100 diamonds were extracted from 12 samples (total weight 815 kg). The crystals are colorless resorbed octahedra and, more seldom, combined octahedra-dodecahedra and spinel twins with abundant green spots caused by natural irradiation, which often make the whole crystal surface green. The diamonds contain inclusions of Mg-rich orthopyroxene and pentlandite suggestive of peridotitic lithospheric mantle derivation and dating of the sulfide inclusion implies a late Archean mantle source. By petrochemistry, the rocks are classified as kimberlites. The Kimozero kimberlites differ from classical Phanerozoic ones in having higher Fe contents, low contents of alkalies and P 2O 5, and intense superimposed carbonate, magnetite, and amphibole mineralization. The saucer-like bodies with narrow feeders without developed diatremes have no analogs in Russia but are similar to the saucer-like kimberlite bodies in Canada (Fort a la Corne), India (Tokapal), and Central Africa (Bakwanga) and the West Kimberley lamproites in Australia. By analogy with these bodies and on the basis of some common petrographic features (presence of pyroclastics and specific amoeba-like autoliths, scarcity of fragments of the enclosing rocks, local reworking of the deposited matter), the Kimozero kimberlites are considered to be the products of subaerial volcanic central-type eruptions.

DISTRIBUTION OF MINERAL RESOURCES AND AGGREGATES IN SAMBAS WATERS, WEST KALIMANTAN PROVINCE

Marine sediments of Sambas Waters, West Kalimantan, contain of five groups of minerals such as hydroxide oxides, silicates, sulfides, and carbonates. The dominant mineral in hydroxide oxides group is magnetite that composes about 0.00720% and lowest is 0.00310% of the sediments, followed by hematite, limonite, and rutile. Augite being the dominant mineral in silicate group was found in six samples with highest percentage of 0,.0091%, followed by casiterite and hornblende. Phyrite from the sulfide group, is present in six samples of seven sediment samples with average percentage of <1%. Dolomite is the only mineral that represents carbonate group and it was found in 7 samples with average percentage of less than 1%. While Mica minerals that occur in the study area are muscovite. Muscovite was observed in four sample of seven samples analysed, with highest percentage of 0.000771% and the lowest 0.00018%.Aggregates that have been exploited in the study area are andesite, dacite and sands that compose the alluvium and old volcanic units.

Regional trends in the chemical and mineralogical properties of upland soils in humid Asia: With special reference to the WRB classification scheme

Soils in humid Asia exhibit relatively incipient mineralogical characteristics because of the dominant steep slopes, crust movement and volcanic activity compared with many tropical soils on stable plains. In the present study, the relationship between the mineralogical and chemical properties of these soils was investigated with special reference to the World Reference Base (WRB) classification scheme. A total of 186 upland soil profiles were collected and the chemical and mineralogical properties of the B-horizon soils were analyzed for clay mineral composition, pH(H2O), exchangeable cations, cation exchange capacity (CEC), total C content, particle size distribution and sodium-dithionite-extractable oxides (Fed and Ald). The majority of the soils were acidic. The CEC/clay of the soils derived from sedimentary rocks (excluding limestone) or felsic parent materials showed a clear regional trend, which was usually higher than 24 cmolc kg−1 (corresponding to Alisols if the argic horizon is recognized) under the udic and perudic soil moisture regimes in Indonesia and Japan, whereas it was predominantly lower than 24 cmolc kg−1 (corresponding to Acrisols) under the ustic soil moisture regime in Thailand. In contrast, soils derived from mafic volcanic rocks or limestone were more variable in clay mineral composition, CEC/clay and pH, and were often high in Fed. This trend is in accordance with the clay mineral composition, in that mica and kaolin minerals dominated under the ustic soil moisture regime in Thailand, whereas significant amounts of 1.4 nm minerals formed under the udic and perudic soil moisture regimes in Japan and Indonesia. In conclusion, of the 186 soils studied, only nine and eight soils are classified into Luvisols (or Lixisols) and Cambisols (eutric), respectively, whereas the majority (169 samples) are classified as acid soils, such as Andosols, Podzols, Alisols, Acrisols and Cambisols (dystric). The WRB classification is generally consistent with regional trends in the chemical and mineralogical properties of the soils and successfully describes the distribution patterns of the acid soils in humid Asia using the criteria of CEC/clay = 24 cmolc kg−1.

Application of sericite to LWC coatings

Sericite is a mica mineral locally produced from the east coast of Taiwan. It carries high negative charges on its plate surfaces and has a high aspect ratio that might be useful for adjusting water retention values and the viscosity of coating colors. In this study, we partially or totally replaced delaminated clay in a lightweight coating (LWC) formulation with sericite and examined the resulting effects on the optical and printing properties of the coating colors and coated sheets. The water retention value (WRV) of the color decreased with increasing amounts of sericite substitution, reflecting an increase in water retention of the color by about 30%. Low shear viscosities decreased with increasing amounts of sericite substitution, while high shear viscosities showed a V-shaped response, suggesting an increase in the elasticity of the coating color under high shear conditions. Among the coated paper properties, the addition of sericite raised the opacity of the sheet. The brightness of the coated sheets, however, decreased linearly with increasing sericite substitution. When sericite was applied, notable swelling and delamination effects occurred during the preparation of the coating color.

Physical elution in phage display selection of inorganic-binding peptides

Phage display is a commonly utilized in vivo approach in selecting peptides specific to solid inorganic materials. In this process, traditionally, high affinity peptides are recovered by a chemical elution method, which involves contacting the phage library with the desired inorganic, washing the weak binders, and eluting the tight binders under harsh buffer conditions. This process may result in incomplete removal of all strong binders, separation of the phage from the display protein, or may modify the material surface. To overcome these potential limitations, we developed a physical elution technique based on ultrasonication. Here, we report two optimized ultrasonication protocols by which we selected peptides specific to natural mineral mica. We first performed a 30-s physical elution after the chemical elution step and increased the efficiency of screening strong binders by about 100%. Encouraged by the results, we applied physical elution-only protocol where we obtained 45% of the selected sequences as strong binders. The approach has a far shorter total elution time, i.e., seconds compared to hours in traditional chemical elution. The novel physical elution approach using ultrasonication reported herein can be a highly efficient alternate step in the screening of solid material specific peptides.

Detection of pre-defined boundaries between hydrothermal alteration zones using rotation-variant template matching

A new method for the detection of pre-defined boundaries in single-band image data that uses a rotation-variant template matching (RTM) algorithm is presented. This algorithm matches a miniature image of a pre-defined boundary to image data at various orientations. The image pixels that match boundary criteria are reported in output imagery together with the rotation angle of the template. The method is applied to identify boundaries between hydrothermal alteration zones in processed airborne hyperspectral imagery, based on the presence of white mica minerals. Results show that boundaries identified with RTM are relatively free of noise and more coherent than those identified with, for instance, image slicing techniques. Identified boundaries can be used for image segmentation. The output of the RTM algorithm also provides information on the type of boundary, whether it is crisp or gradual. This information can be used to better characterize mineral variation in the alteration halo associated with fossil hydrothermal systems.

Effect of temperature on the sorption behavior of sodium potassium fluorophlogopite with respect to the heavy metal ions Cd2+, Hg2+, and Pb2+

The effect of temperature on the sorption behavior of a synthesized gel structurally close to the fluorine mica mineral, sodium potassium fluorophologopite, was studied for the heavy metal ions Cd2+, Hg2+, and Pb2+. The synthesized gel was characterized by X-ray powder pattern, energy dispersive spectrometry, infrared spectroscopy, and thermogravimetric analysis and was found to have the composition Na0.5K0.5Mg(AlSi3O10)F2·6H2O. The effect of temperature on sorption was studied with respect to varying concentrations of metal ions. The overall sorption capacity of the synthesized gel was found to depend on the number of ion active groups per unit weight of the material. The data were expressed in terms of distribution coefficients (Kd). Sorption data followed Freundlich adsorption isotherms. Studies showed that sorption decreased as the concentration of metal ions increased and increased as the temperature grew, which was evidence that the process was endothermic.

Clay mineral formation during podzolization in an alpine environment of the Tatra Mountains, Poland

AbstractThe processes of clay mineral formation were studied in seven podzol profiles developed on granitic regoliths in the Polish part of the Tatra Mountains. The selected profiles have similar parent material and macroscopically represent different stages of soil development (from initial to advanced). Bulk soil material (<2 mm fraction) and separated clay fractions (<2 µm) were studied using a petrographic microscope, X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy-energy-dispersive spectrometry methods. The mineral compositions of the bulk soil samples are more or less the same (quartz, feldspars, mica and minor amounts of other phyllosilicates). The clay fractions are composed of mica and mixed-layer minerals which contain hydrated interlayers of vermiculitic and/or smectitic type, and kaolinite. Smaller amounts of chlorite, feldspars and quartz were also identified. Chlorite is present almost exclusively (except for one profile) in lower soil horizons (C, B/C, B). The amount of minerals with hydrated interlayers increases up the profiles. Kaolinite is present in all the samples except for the lowermost soil horizons (C) of two of the profiles. In some of the B horizons, the formation of hydroxy interlayers within hydrated interlayers is observed. The main processes of clay mineral formation recognized in the soils studied are: inheritance from the parent rocks; crystallization of kaolinite from soil solutions; the formation of dioctahedral vermiculite at the expense of inherited dioctahedral mica, and the formation of dioctahedral smectite at the expense of vermiculite. The recognized sequence of transformation is as follows: M → R0 M-V (12 Å or 14 Å) → R0 M-12 Å V → R1 M-12 Å V → 12 Å V → V-S → S. Observed formation of hydroxy interlayers seems to be pH dependent, starting when the pH ⩾ 4.4. The process of dissolution of primary silicates occurring simultaneously with the transformation is also documented.

Recovery of Pd(II) and Ru(III) from aqueous waste using inorganic ion-exchanger

The applicability of mica minerals and zeolites for the efficient removal of valuable platinum group metals (PGMs), Pd(II) and Ru(III) from aqueous waste by sorption has been investigated. The sorption of PGMs Pd(II) onto mica-mineral, muscovite and Ru(III) onto natrolite as zeolite have been studied as a function of (i) exchanger composition, (ii) temperature at which sorption process takes place and (iii) the presence of competing cations such as Na+, K+, Mg2+. These three factors have remarkable effect on the sorption process. The synthesized gel was characterized by X-ray powder diffraction, energy dispersive spectrometry, thermogravimetric analysis and scanning electron microscopy.

Drill core LB‐08A, Bosumtwi impact structure, Ghana: Petrographic and shock metamorphic studies of material from the central uplift

Abstract— During a recent drilling project sponsored by the International Continental Scientific Drilling Progam (ICDP), two boreholes (LB‐07A and LB‐08A) were drilled into the crater fill of the Bosumtwi impact structure and the underlying basement, into the deep crater moat and the outer flank of the central uplift, respectively. The Bosumtwi impact structure in Ghana (West Africa), which is 10.5 km in diameter and 1.07 Myr old, is largely filled by Lake Bosumtwi.Here we present the lithostratigraphy of drill core LB‐08A (recovered between 235.6 and 451.33 m depth below lake level) as well as the first mineralogical and petrographic observations of samples from this core. This drill core consists of approximately 25 m of polymict, clast‐supported lithic breccia intercalated with suevite, which overlies fractured/brecciated metasediment that displays a large variation in lithology and grain size. The lithologies present in the central uplift are metasediments composed dominantly of fine‐grained to gritty meta‐graywacke, phyllite, and slate, as well as suevite and polymict lithic impact breccia. The suevites, principally present between 235.6 and 240.5 m and between 257.6 and 262.2 m, display a fine‐grained fragmental matrix (about 39 to 45 vol%) and a variety of lithic and mineral clasts that include meta‐graywacke, phyllite, slate, quartzite, carbon‐rich organic shale, and calcite, as well as melt particles, fractured quartz, unshocked quartz, unshocked feldspar, quartz with planar deformation features (PDFs), diaplectic quartz glass, mica, epidote, sphene, and opaque minerals). The crater‐fill suevite contains calcite clasts but no granite clasts, in contrast to suevite from outside the northern crater rim.The presence of melt particles in suevite samples from the uppermost 25 meters of the core and in suevite dikelets in the basement is an indicator of shock pressures exceeding 45 GPa. Quartz grains present in suevite and polymict lithic impact breccia abundantly display 1 to (rarely) 4 sets of PDFs per grain. The shock pressures recorded by the PDFs in quartz grains in the polymict impact breccia range from 10 to ∼30 GPa. We also observed a decrease of the abundance of shocked quartz grains in the brecciated basement with increasing depth. Meta‐graywacke samples from the basement are heterogeneously shocked, with shock pressures locally ranging up to 25–30 GPa. Suevites from this borehole show a lower proportion of melt particles and diaplectic quartz glass than suevites from outside the northern crater rim (fallback impact breccia), as well as a lack of ballen quartz, which is present in the external breccias. Similar variations of melt‐particle abundance and shock‐metamorphic grade between impact‐breccia deposits within the crater and fallout impact breccia outside the crater have been observed at the Ries impact structure, Germany.

Removal of chromium(II), iron(III) and nickel(II) by synthetic analogue of mica mineral sodium potassium fluorophlogopite

Removal of chromium(II), iron(III) and nickel(II) by synthetic analogue of mica mineral sodium potassium fluorophlogopite

Dust as a Nutrient Source for Fynbos Ecosystems, South Africa

Fynbos is the main vegetation of the Cape Floristic Region, a biodiversity hotspot that occurs in southwestern South Africa. A major question concerning the fynbos ecosystem is how it supports abundant and diverse vegetation on soils derived from nutrient-poor bedrock. In addition to marine aerosols (recycled sea salts), geochemical analyses reported here suggest that dust (aeolian) deposition represents a significant source of nutrients (for example, K, Ca and Zn) to the fynbos ecosystem. Headwater portions of the Boontjies River sub-catchment near the Cederberg Mountains support mountain fynbos communities that are entirely underlain by the Peninsula Formation, a quartz arenite with greater than 98 wt% SiO2. Fynbos soils in these areas are composed of quartzose sand with 3–6 wt% kaolinitic clay and 1–2 wt% organic carbon. The minor amount of feldspar and mica minerals in the bedrock (0.5 wt% Al2O3) suggests an aeolian source for much of the clay minerals in the soil. The isotope composition of soluble Pb and Sr from fynbos vegetation and soils indicates a mixture of anthropogenic and terrigenous sources, most likely from washout of combusted petrol and dust from the arid interior particularly in association with Berg Wind events. Approximate mass balance calculations indicate that washout of aerosols provides an important source of nutrients such as Ca, K, P, Fe, Mn and Zn which the fynbos ecosystem is highly effective in retaining.

A study of the crystalline structure of vermiculite from the Tebinbulak deposit

The results of studies of vermiculite rock from the Tebinbulak deposit are given. It is established that this vermiculite rock consists of biotite mica minerals. The crystalline lattice of these minerals contains interpack water known as zeolite water, which is responsible for swelling of the rock in heating. Vermiculite rock fired at 200–900°C is capable of absorbing water, i.e., of rehydration. This is important in using swelled vermiculite in the production of fire-retardant paints. The compositions of fire-retardant paints and the results of their testing for heat resistance according to GOST 30402 are given. It is established that all the developed mixtures impart fired-retardant properties to timber.

Global cooling forced increase in marine strontium isotopic ratios: Importance of mica weathering and a kinetic approach

The knowledge of how and why marine 87Sr/ 86Sr ratios changed helps understand the impacts of many processes on the global biogeochemical cycle in the geological past. Here we examine the possible influence of global cooling on the evolution of marine 87Sr/ 86Sr curve by a kinetic approach. The importance of mica weathering is emphasized due to its high content of radiogenic strontium and low activation energy in weathering reaction. Since the activation energy determines the sensitivity of weathering rate in response to temperature changes, global cooling will increase the 87Sr/ 86Sr ratio of continental flux by relatively preferential weathering of mica. Based on the average strontium contents and 87Sr/ 86Sr ratios of the mica minerals in the exposed upper continental crust, a kinetic model is established to survey the response of riverine 87Sr/ 86Sr to the changes of global temperatures. The model result indicates that the increase of riverine 87Sr/ 86Sr caused by global cooling can solely account for most of the increase in seawater 87Sr/ 86Sr since 3.4 Myr B.P. This finding emphasizes that the weathering kinetics is an important mechanism relating the global climate change to marine 87Sr/ 86Sr curve; and the marine 87Sr/ 86Sr curve should be used with great care in the climate-weathering-tectonic connections.

Reappraisal of early Paleogene CCD curves: foraminiferal assemblages and stable carbon isotopes across the carbonate facies of Perth Abyssal Plain

Bulk carbonate content, planktic and benthic foraminiferal assemblages, stable isotope compositions of bulk carbonate and Nuttallides truempyi (benthic foraminifera), and non-carbonate mineralogy were examined across ∼30 m of carbonate-rich Paleogene sediment at Deep Sea Drilling Project (DSDP) Site 259, on Perth Abyssal Plain off Western Australia. Carbonate content, mostly reflecting nannofossil abundance, ranges from 3 to 80% and generally exceeds 50% between 35 and 57 mbsf. A clay-rich horizon with a carbonate content of about 37% occurs between 55.17 and 55.37 mbsf. The carbonate-rich interval spans planktic foraminiferal zones P4c to P6b (∼57–52 Ma), with the clay-rich horizon near the base of our Zone P5 (upper)—P6b. Throughout the studied interval, benthic species dominate foraminiferal assemblages, with scarce planktic foraminifera usually of poor preservation and limited species diversity. A prominent Benthic Foraminiferal Extinction Event (BFEE) occurs across the clay-rich horizon, with an influx of large Acarinina immediately above. The δ13C records of bulk carbonate and N. truempyi exhibit trends similar to those observed in upper Paleocene–lower Eocene (∼57–52 Ma) sediment from other locations. Two successive decreases in bulk carbonate and N. truempyi δ13C of 0.5 and 1.0‰ characterize the interval at and immediately above the BFEE. Despite major changes in carbonate content, foraminiferal assemblages and carbon isotopes, the mineralogy of the non-carbonate fraction consistently comprises expanding clay, heulandite (zeolite), quartz, feldspar (sodic or calcic), minor mica, and pyrolusite (MnO2). The uniformity of this mineral assemblage suggests that Site 259 received similar non-carbonate sediment before, during and after pelagic carbonate deposition. The carbonate plug at Site 259 probably represents a drop in the CCD from ∼57 to 52–51 Ma, as also recognized at other locations.

C- and Sr-isotope systematics applied to Neoproterozoic marbles of the Seridó belt, northeastern Brazil

The Seridó fold belt, situated in the northeastern part of the Borborema Province in northeastern Brazil, has been the target of several studies in the last two decades. Previous field and structural studies suggested a Paleoproterozoic age, but recent isotopic data raised the possibility that the original sediments were deposited and metamorphosed during the Neoproterozoic. Detailed C and Sr isotope studies in marbles of the Seridó Group clarify this issue. In the Jucurutu Formation, at the base of the Seridó Group, δ 13C fluctuations indicate three stratigraphic levels of carbonate sedimentation. Basal marbles, consisting of calcite, amphibole, phlogopite, quartz and opaques, display δ 13C between + 8.3 and + 10.8‰ V-PDB. Values of δ 13C < + 8.3‰ V-PDB are observed in marble samples close to the contact with metapelites, or when silicate minerals are more abundant. Intermediate marbles are composed of calcite, tremolite, phlogopite, quartz, opaques, and wollastonite and exhibit δ 13C values from + 6.7 to + 8.7‰ V-PDB. In wollastonite-bearing marbles, δ 13C is < + 6.7‰ V-PDB (sometimes negative). The youngest Jucurutu Formation marbles, consisting of calcite, dolomite, amphibole, mica, quartz, and opaque minerals in variable amounts, had δ 13C values from − 8.9 to + 3.8‰ V-PDB. δ 13C varies according to the abundance of silicate minerals present and with the calcite/dolomite ratio. Basal marbles of the Seridó Formation, composed of calcite, tremolite, phlogopite, quartz and opaques, exhibit δ 13C values from + 8.9 to + 10.7‰ V-PDB. A gradual declining δ 13C (+ 7.5 to + 4.4‰ V-PDB) coincident with an increase in silicate content, marks the basal contact with mica-schists. Negative δ 13C values mark the upper calcitic marble (± phlogopite) intercalations of the Seridó belt that exhibit values from − 4.6 to − 4.0‰ V-PDB. The C-isotope compositions observed in marbles of the Seridó belt vs. the C-isotope secular variation curve, suggest depositional age interval of 590–570 Ma. This is further corroborated by the Sr-isotope ratios (mostly between 0.7074 and 0.7077), typical of pre-Varangerian carbonates.

Strain and texture measurements on geological samples using neutron diffraction at IBR-2, Joint Institute for Nuclear Research, Dubna (Russia)

Information on texture and residual stress in geological samples is very important for the calculation of physical properties connected with the evaluation of the geomechanical behavior of parts of the earths’s crust in connection with processes from human activities (mining, tunnelling) and natural processes of deformation (seismicity, earthquakes). Texture and stress are not independent of each other and in the general case should be analyzed together. Complications arise because geological samples are generally composed of several phases (minerals) whose elastic constants may be significantly different. Nevertheless, modern neutron diffractometers such as SKAT and EPSILON-MDS at the fast pulsed reactor IBR-2 at the FLNP of the JINR make it possible to obtain the needed diffraction patterns. This was shown especially for texture measurements on samples with quartz as the main component as well as for mica, feldspar, amphibole, and several other minerals. In order to extend strain measurements beyond samples composed of quartz, dolomite, and/or anhydrite to such frequently occurring minerals as feldspars and mica it would be necessary on the one hand to use Rietveld refinement with corrections due to texture and anisotropic peak broadening. With an increase in the number of mineral phases suitable for these diffractometers, it is in general necessary to improve the experimental conditions for SKAT and EPSILON-MDS, especially to significantly raise the flux of incident neutrons on the sample.

Opal-A rich additives used in ancient lime mortars

Ancient stone and brick masonry mortars from three monuments in Konya, Central Anatolia dated to the Anatolian Selçuk Period (12th and 13th centuries AD) were examined for their raw material composition and durability characteristics to understand some characteristics of medieval mortar technology. Optical microscopy, XRD, SEM, EDX, FTIR and TGA analyses revealed that the mortars contained high percentage of lime binder totally carbonated into micritic calcite. Coarse and medium aggregates were mainly composed of sandstone and metamorphic rock fragments, quartz, feldspar and mica minerals. Opal-A was found in considerable amounts in the fine aggregates, likely not derived from the coarser ones but added separately. Pozzolanic activity of the fine aggregates was determined by conductometric measurements. Their ability to form C-S-H was observed by treating them with saturated Ca(OH) 2 solution. Bulk density and total porosity measurements showed that the mortars were highly porous due to the use of high amount of lime. On the other hand, they possessed sufficient mechanical strength. Mechanical properties were determined by point load tests and ultrasonic pulse velocity measurements. They were expressed as uniaxial compressive strength (UCS) and modulus of elasticity ( E mod) in MPa. The results were also discussed in terms of durability characteristics of the mortars. They were expressed with the use of uniaxial compressive strengths in dry and wet states, and total porosity values. The mortars were considered to have high durability to wetting and drying cycles but had poor durability to the crystallization of water-soluble salts.

Geochronology of the Pengjiakuang and Rushan Gold Deposits, Eastern Jiaodong Gold Province, Northeastern China: Implications for Regional Mineralization and Geodynamic Setting

The Jiaodong gold province, the largest gold-producing district in China, is located in the jiaodong peninsula at the eastern margin of the North China craton and bounded by the continental scale Tan-Lu fault, 40 kin to the west. Previous geochronological studies suggest that pervasive gold deposition took place in the western part of the province between 122 and 119 Ma. Here we report high-quality Ar-40/Ar-39 ages of the Pengjiakuang and Rushan deposits from the eastern part of the jiaodong gold province, placing additional chronological constraints on the timing of regional mineralization. Seven sericite grains extracted from auriferous alteration assemblages at the Pengiiakuang deposit yielded well-defined plateau ages between 120.9 +/- 0.4 and 119.1 +/- 0.2 Ma (2 sigma). Three separates of igneous biotite from a sample of the Queshan gneissic granite, adjacent to the Pengjiakuang deposit, gave reproducible plateau ages of 124.6 +/- 0.6 to 123.9 +/- 0.4 Ma (2 sigma). Six sericite separates front two samples in the Rushan deposit yielded Ar-40/Ar-39 plateau ages at 109.3 +/- 0.3 to 107.7 +/- 0.5 Ma (2 sigma), whereas biotite from the Kunyushan monzogranite that hosts the Rushan deposit had plateau ages ranging from 129.0 +/- 0.6 to 126.9 +/- 0.6 Ma (3 separates front one sample). The apparent age gap between hydrothermal sericite and magmtic biotite from both deposits, together with the similar argon closure temperatures for these mica minerals, suggest that gold mineralization had no direct relationship to the granitoid magmatism. Instead, gold deposition coincided with the emplacement of mafic to intermediate dikes widespread in the jiaodong gold province, which have been dated at ca. 122 to 119 Ma and, less commonly, at 110 to 102 Ma. The new Ar-40/Ar-39 ages from the eastern jiaodong peninsula, when combined with published data from the western part suggest that gold mineralization was broadly contemporaneous throughout the district. The Early Cretaceous gold mineralization also is widely developed in four other major gold districts along the Tan-Lu fault. The temporal and spatial correlation of these gold deposits with mafic to intermediate dikes commonly found in most mineralized areas, the presence of well-documented metamorphic core complexes and half-graben basins along the Tan-Lu fault, and voluminous basalts therein, suggest that the Early Cretaceous was an important period of lithospheric extension, possibly caused by the late Mesozoic lithospheric thinning beneath the eastern block of the North China craton. Lithospheric thinning and extension could have resulted in abnormally high heat and fluid fluxes necessary for large-scaled gold mineralization.