Different Types Of Quartz Research Articles

NUEVOS ASPECTOS GEOLÓGICO-MINEROS SOBRE EL YACIMIENTO DE BOLIVIANITA ANAHÍ, UBICADO EN EL ORIENTE BOLIVIANO

A recent investigation of the bolivianita Anahi mine reveals that the mineralization is the product of intracratonic thermal fluids which migrated along a deep lineament and through a basin with an Upper Proterozoic sediment filling. The mineralization is hosted by Cambrian limestone and related to a collapse structure. It occurs within caverns of dissolution, fractures and open spaces which were formed by karstic processes and circulation of thermal fluids. The different types of quartz precipitated by mixing of ascendant thermal fluids enriched in silica with descendent cold meteoric water close to the paleo-surface. The geometry of the mineralizacion follows the subterraneous morphology of the paleo-karst. The amorphous silica precipitated close or on top of the paleo-aquifer as opal-chalcedony with some disseminated pyrite. The crystalline gem quartz grew below this sinter cap. The exact age of the mineralization is unknown. But it is most likely that the process of selective dissolution of the Cambrian limestone started after its consolidation during a phase of continental uplift of the regolith under humid climate and continues until today. The migration of thermal fluids was probably induced by Upper Cretaceous alkaline igneous activity.

A Comparative Study on the Composition of the Clastic and the Parent Rock of the Source Area in the Yanchang Formation in the Longdong Area of the Ordos Basin

Based on the data of element geochemistry, electron probe, tectonic attributes, etc., the composition of the clastic and parent rock in the source area was analyzed for the Yanchang Formation in Longdong area. Research shows that the Yanchang Formation includes single crystal quartz, polycrystalline quartz, bicyclic quartz, fragmented quartz, dust-rich turbid quartz, and wavy matte quartz. Different types of quartz come from different parent rocks in different areas of the basin. Feldspar mainly comes from Guanshan pluton, Cuihua mountain, Haiyuan, and Longxi intermediate acid biotite granite in the periphery of the basin. In the Yanchang Formation in the study area, most of the heavy minerals in the sandstone formed by the northeast provenance come from the metamorphic parent rock in the Yinshan area, while the heavy minerals in the sandstone formed by the southwest provenance are formed in the hydrothermal metamorphic parent rock. The content of heavy minerals varies greatly in different depositional stages, and the provenance direction of sandstone in different intervals and the type of parent rock in the source area vary. The cuttings particles have a long transport distance, fine particle size, little cuttings retention, poor stability of rock structure and composition, weak resistance to weathering, and low cuttings content.

Silica diagenesis in the Lower Paleozoic Wufeng and Longmaxi Formations in the Sichuan Basin, South China: Implications for reservoir properties and paleoproductivity

Silica diagenesis is one of the most important aspects of black shale diagenesis and critically controls the reservoirs properties of black shales. Three stratigraphic sections of the Wufeng and Longmaxi Formations in the Sichuan Basin along a proximal to distal transect were investigated to study quartz types and their silica sources, as well as their influences on reservoirs properties including rock mechanical properties and porosity preservation. Six types of quartz including detrital quartz, recrystallized radiolaria, siliceous fossil fragments, microcrystalline quartz, quartz overgrowth, and hydrothermal quartz veins were identified based on their occurrences and morphologies under the petrographic microscope and scanning electron microscope and cathodoluminescence color and intensity. Original biogenic silica now exists as recrystallized radiolaria and microcrystalline silica in the mudstone matrix and follows systematic distribution patterns both laterally and stratigraphically. The biological origin of this silica component is supported by the presence of recrystallized radiolaria with preserved spines, preservation of “ghosts” of the central capsule, serrated edges reflecting the spherical lattices of the outer shell, and in addition preserved sponge spicules. A further source of silica for microcrystalline quartz formation was silica released in the course of clay mineral (smectite to illite) transformation.The different types of quartz make different contributions to the reservoir properties of shales, with microcrystalline quartz having the most important impact. Microcrystalline quartz enhances the rock mechanical properties of shales and protects initial porosity from mechanical compaction through a rigid framework of interconnected diagenetic silica grains. Pores between microcrystalline quartz grains are shielded from complete mechanical compaction and provide space for accumulation of bitumen and oil later in burial history. Subsequently, these pore-filling organic matter develop secondary organic nanopores at higher thermal maturity.Although biogenic silica content has been used as a paleoproductivity proxy, the method used to calculate it is based on questionable assumptions, and model parameters need to be fine-tuned for a given shale succession on the basis of petrographic observations. In addition, the commonly observed positive correlation between total organic carbon (TOC) and biogenic silica is invalid for very low sedimentation rates and extremely high concentrations of biogenic silica. From low to extremely high biogenic silica content in organic-rich sediments, a parabolic relationship between TOC and biogenic silica should be common.

Evaluation of ASTER TIR data-based lithological indices in Malanjkhand Copper Mines of Madhya Pradesh, India

ABSTRACTThis study focuses on the Malanjkhand Copper Mines area of Madhya Pradesh, India and compares different types of quartz, feldspar and mafic remote sensing indices used for the detection of quartz, feldspar and mafic minerals using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) thermal infrared (TIR) bands. Our data indicate that these lithological indices are useful for delineating quartz, feldspar or mafic minerals. Correlation matrices generated for various lithological indices indicate that both Guha's (GMI) and Ninomiya's (NMI) mafic indices yield nearly identical results. In addition, Guha's quartz index (GQI) yields significantly better results than Ninomiya's quartz index (NQI) during the identification of the quartz content. This study also shows that GQI is comparable with the Rockwall and Hofstra's quartz index (RHQI) for the identification of the quartz content. Hence, ASTER TIR data-based remote sensing indices play a key role in lithological mapping.

Investigation of the spectrally resolved TL peaks of quartz in the 70°C–220°C temperature region

In this work, we investigate the thermoluminescence emission in the temperature range 70 °C–220 °C for different types of quartz, both natural and synthetic. We focus on three thermoluminescence peaks, the so called 110 °C one, which we detect at around 85 °C (5 °C/s), and the two intermediate peaks detected at about 150 °C and 200 °C. The effect of thermal annealing at 500 °C and 1000 °C on the glow curves are also considered. Using interference filters and, for selected samples, a wavelength resolved detection system, we analyse the different spectral components of the peaks. It turns out that the spectral emission of the three peaks is significantly different. The 85 °C peak shows the simultaneous emission of at least two UV bands, together with a blue and a red contribution. The two peaks at higher temperature spectra are identical and involve only a single UV emission band.

Trace Element Geochemistry in Quartz in the Jinqingding Gold Deposit, Jiaodong Peninsula, China: Implications for the Gold Precipitation Mechanism

Lots of studies on gold precipitation mechanisms have focused on fluid inclusions within quartz. However, the trace elements in quartz reflect the properties of the ore fluid, and a comparison of the trace element content in different types of quartz can reveal the precipitation mechanism. The Jinqingding gold deposit is the largest gold deposit in the Muping–Rushan gold belt and contains the largest single sulfide–quartz vein type orebody in the gold belt. This study distinguished four types of quartz in this orebody through field work and investigations of the mineralogy and cathodoluminescence (CL) of the quartz and crosscutting relationships as seen under a microscope. In situ studies via electron probe micro-analyzer (EPMA) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) were used to determine the trace element content of the different quartz types. Type Qa displayed a comb structure in the field and zoning under the microscope and in CL. Milky white and smoke grey Qb was the most common quartz type and hosted the most sulfide and gold. Qc was Qa and Qb quartz that recrystallized around pyrite or overgrew and appeared different from Qa and Qb in CL images. Qd occurred within fractures in pyrite. Qa formed prior to the mineralization of gold, and Qd formed post-mineralization. Qb and Qc provided information regarding the ore fluid during mineralization. Sericites occurred with pyrite in fractures in the quartz, and some, along with free gold, filled in fractures in pyrite. Free gold occurred within Qa, Qb, Qc, and in brittle fractures in pyrite. Qc had the lowest Al content of all of the quartz types. As Al content is related to the acidity of the ore fluid in previous study, this indicated an acidity decrease during mineralization, which could be attributed to the sericitization. Sericitization could indicate a potential gold occurrence. The Ti content decreased from Qb to Qc, indicating a decrease in temperature during quartz overgrowth formation. Change in acidity and cooling can therefore be identified as possible causes of gold precipitation in the sulfide–quartz vein type in the Jinqingding gold deposit.

Origin of quartz in the lower Cambrian Niutitang Formation in south Hubei Province, upper Yangtze platform

Abstract Brittle minerals, especially quartz, play an important role in the quality of shale reservoir. The precipitation of authigenic quartz caused a significant change in the rock stiffness and porosity. However, the formation mechanism of authigenic quartz in shale is still unclear. Lower Cambrian Niutitang shale from Guchengcun outcrop has been examined with respect to quartz cement. Four different types of quartz have been identified using SEM/CL/EDS. Type 1 occurs as angular to sub-rounded silt-size quartz grains with uniform luminescence, indicative of detrital origin. Type 2 appears as relatively large quartz aggregates approximately 30–150 μm in size, which is composed of small quartz grains (1–3 μm) and abundant in siliceous shale. The petrological evidence and consideration of potential diagenetic process suggest that Type 2 quartz was formed by local re-crystallization of biogenic silica in syndiagenesis and preferentially precipitated in the axial cavities of sponge spicules. Type 3 occurs as quartz overgrowths that are essentially non-luminescent at the periphery of high luminescence detrital quartz grains. This type quartz is present in most investigated samples. Type 4 represents microcrystalline quartz embedded in the illitized clay matrix as discrete, short chains or small clusters/nests and they are most commonly observed in argillaceous shale. The petrological evidence and CL responses indicate that both Type 3 and Type 4 quartz are derived from precipitation of silica released during the smectite to illite dissolution–precipitation reaction. S-I transition can be driven by microbial metabolic processes in shallow buried diagenesis or by heat and pressure in late diagenesis. Some of Type 4 quartz may be originated from low-temperature microbial pathway in shallow buried diagenesis, while Type 3 quartz and the remaining Type 4 quartz were formed in late diagenesis. Siliceous shale contains less abundant detrital quartz than argillaceous shale, indicating that siliceous shale was deposited in deeper water and far from terrigenous input than argillaceous shale. Although identifying the exact cause for diagenetic silica deposition in shale is not a trivial matter, its recognition is important for the reconstruction of the depositional history of shale sequences and understanding the role of diagenesis in shale reservoirs development, moreover, it also has great potential for enhancing prediction of mechanical rock properties in shales.

Different formation mechanism of quartz in siliceous and argillaceous shales: A case study of Longmaxi Formation in South China

Abstract Brittle mineral, especially quartz, exert significant effect on the development of shale gas, however, the formation mechanism of quartz in shale is still unclear. Here, we present X-ray diffraction data, scanning electron microscopy (SEM) determination, cathodoluminescence and geochemical data to investigate Longmaxi Formation, which is a key target for shale gas exploration and development in China recently. Siliceous and argillaceous mudstones were recognized from 5 outcrops of Longmaxi Formation, which were examined with respect to the formation mechamism of quartz. Three different types of quartz (silt-size detrital grain with bright luminescence, micro-sized grains and quartz overgrowths with bright luminescence) were identified by SEM/EDS/CL both in the argillaceous and siliceous shale. Siliceous shale deposited by suspension sediment settling with high sea level because of anoxia condition indicated by lower Th/U and higher V/Cr ratios. The quartz in siliceous shale display a positive covariation with Babio, as well as a good correlation between TOC and quartz, suggesting biogenic-quartz is an important constituents. Argillaceous shale was likely dominated by suspension alternate with gravity current in consideration of the mixing of clay- and silt-laminae, there is no correlation between quartz and TOC, and positive correlation between excess silica and Zr, indicating terrestrial quartz in argillaceous is more important relative to siliceous shale. Additionally, reorientation of phyllosilicate particles and positive correlation between KI and quartz contents (R2 = 0.57) suggest the indispensable diagenetic-quartz (illitization of smectite), near or far from the clay minerals, both in siliceous and argillaceous shales. This process also result in high quartz saturation in silt-rich laminae, thus that quartz overgrowths encased in dolomite cements is common in argillaceous shale. Based on the geochemical analysis, the argillaceous shale contains 86% detrital-silica, 14% digenetic-silica. However, the siliceous shale approximately contains 33% detrital-silica, 11% digenetic-silica and 56% biogenic-silica. Occurrence and origin of quartz are of great significance for physical properties of shale and hydraulic fracturing during the development of shale gas.

Variability of the rebound hardness as a proxy for detecting the levels of continuity and isotropy in archaeological quartz

The Equotip Hardness Tester is applied to different types of quartz and other lithic raw materials in order to determine if variations in the rebound hardness measured by this device may serve as a proxy for detecting the levels of continuity and isotropy of toolstones. Continuity, the amount of cracks and other internal defects; and isotropy, the measure of the directional properties of a raw material, are known to have important effects on the level of consistency and predictability of fractures, which in turn is traditionally considered a main factor for defining the flaking quality of a given raw material.The results demonstrate the existence of differences among the raw materials analysed in both the average value and the variability of the rebound hardness. While cryptocrystalline samples show the most homogeneous results, quartz and metamorphic rocks display a comparatively higher variance. In the specific case of quartz, such variability seems to be mainly caused by the presence of internal planes and discontinuities, while anisotropy, although also active, had played a comparatively modest role. The results achieved by the Equotip Hardness Tester suggest that this device could be successfully used for a basic or preliminary estimating of some of the physical and mechanical properties of stone raw materials. Therefore, it is a potential index test for complementing other, more accurate, laboratory methods.

Quartz from Allchar as monitor for cosmogenic 26Al: Geochemical and petrogenetic constraints

Results of a multidisciplinary study on quartz concentrates (mineralogically separated) and etched concentrates (stoichiometric quartz) from three locations at Allchar (Macedonia) are presented. The investigation of quality and composition of these quartz samples is of great interest because the same material has been previously used as monitor for 26Al Acceleration Mass-Spectrometry (AMS) erosion rate estimates. Two genetically different types of quartz are distinguished in the studied samples which petrologically can be described as hydrothermally altered dacites or quartz latites; i.e. volcanic (QV) and hydrothermal (QH) quartz with relative proportions of QH:QV around 3:2. QH is genetically related to the Allchar Sb–As–Tl–S mineralization having very high Sb (85–785 ppm), As (7.6–78 ppm) and (Tl 3.3–4.0 ppm) contents. This type of quartz is also characterized by very high Li (129–138 ppm), Al (2424–2520 ppm) and Ti (153–219 ppm) concentrations. QV appears to be much less enriched in trace elements having Al and K contents ranging from 0 to 280 ppm and from 50 to 85 ppm, respectively. 26Al AMS measurements were done on the samples containing two genetically different types of quartz but this had no effects on the interpretation and erosion rate determinations. However, the extremely high Al concentrations in the analyzed quartz have generally negative effects, mainly by decreasing 26Al/27Al ratios and thus causing an increase of the detection limit. The disagreement between the results of 26Al AMS analyses and quantitative geomorphologic data for one location is probably caused by different geographical position with respect to the direction of cosmic rays.

Characteristics of LM-OSL from several different types of quartz

We present Linear-Modulation OSL (LM-OSL) curves from several different types of quartz, including sedimentary quartz, bulk rock crystal and synthetic quartz. The LM-OSL method consists of linearly increasing the intensity of the stimulation light while continuously monitoring the OSL emission from the sample. With this technique, one obtains peaks of luminescence intensity versus time ( Bulur, 1996) in which the position of the peak is inversely related to the photoionization cross-section of the trap. The shape of the LM-OSL curve is directly related to the shape of the conventional OSL decay curve in which the stimulating light source is maintained at constant intensity (so-called Continuous-Wave OSL, or CW-OSL). In the latter, the OSL from the traps with the highest photoionization cross-section decays most rapidly with stimulation time, while OSL from those traps with smaller photoionization cross-sections is characterized by longer decay times. In this paper, data are presented comparing the CW-OSL and LM-OSL curves for several different quartz types with particular focus on the changes in the shapes of each of these curves with sample type pre-heat temperature, and measurement temperature. Several different LM-OSL components are found for each sample, each with different photoionization cross-sections, but a universal behavior for quartz is not observed; each sample is different. From the dependence upon pre-heat temperature, features associated with shallow traps can be identified. Traps which empty very rapidly can be observed more easily in the LM-OSL curves than in the conventional CW-OSL curves, and the temperature dependence of the photoionization cross-section for the various components can be clearly discerned.

Observations on the micro-texture and esr spectra of quartz from fault gouge

We have investigated fault gouge samples from a variety of sites in eastern China with ESR, optical and scanning electron microscopy (SEM), X-ray diffraction and cathodoluminescence. The results reveal two different types of quartz, a macrocrystalline and a microcrystalline variety. The macrocrystalline samples show increasing ESR intensities of the E' centre with increasing grain size whilst the microcrystalline samples show the opposite trend. We also found that the dissolution of quartz grains and secondary quartz precipitation on the surface of the grains is significant in some samples, indicating active chemical weathering in these fault zones. The occurrence of secondary quartz has serious implications for the reliability of any dating attempt.

Microstructure of quartz in partially inverted coesite from high-pressure metamorphic rocks

Coesite, a high-pressure polymorph of SiO2, was firstly synthesized by Coes. Naturally occurring coesite has been found in shock metamorphosed rocks, xenoliths in kimberlites, eclogites and metasediments. Coesite in metasediments indicates subduction of slabs of continental crust to depths of at least 90 km. Coesite can only survive obduction (decrease of P,T) as an inclusion in a high strength mineral like garnet (pyrope). Depending on the elastic behavior of the coesite-includmg garnets, coesite is always partially inverted into quartz. Stress associated with the volume increase due to the coesite inversion causes a radiating crack pattern around the including mineral. Complete failure of the pressure vessel results in a replacement of coesite by pseudomorphs of quartz after coesite. The present study intends to find characteristic microstructural features as reliable indicators for quartz pseudomorphs having been pseudomorphs after coesite. Four different types of quartz can be distinguished with respect to the fabric, due to the coesite inversion:

Electron spin resonance of auriferous and barren quartz at beaconsfield, Northern Tasmania

The intensity of ESR spectra of powdered quartz from auriferous veins at Beaconfield is greater that the intensity of the spectra from barren vein quartz at the same locality. Lattice impurities are presumed to be the cause of the electron paramagnetism of the mineralised quartz species. The method can be used for the characterisation of different types of quartz and may provide a tool useful in exploration geochemistry.

Electron spin resonance of auriferous and barren quartz at Beaconsfield, Northern Tasmania

The intensity of ESR spectra of powdered quartz from auriferous veins at Beaconsfield is greater than the intensity of the spectra from barren vein quartz at the same locality. Lattice impurities are presumed to be the cause of the electron paramagnetism of the mineralised quartz species. The method can be used for the characterisation of different types of quartz and may provide a tool useful in exploration geochemistry.

On the dose-rate dependence of the thermoluminescence response of quartz

The dose-rate dependence of the thermoluminescence of different types of quartz in the range from 0.8 to 900 rad/min has been measured. This dependence, which is strong for massive quartz, decreases with the irradiation temperature of the samples.

Effects of X-Ray Irradiation on the Frequency-Temperature Behavior ofAT-Cut Quartz Resonators

Results of an investigation of the effects of x-ray irradiation on AT- cut resonators fabricated from natural quartz, synthetic quartz grown on several different cuts of seed plates, and synthetic quartz containing aluminum or germanium as an impurity are reported. The differences in the frequency- temperature characteristics of AT-cut resonators fabricated from natural quartz and all synthetic quartz investigated are known. These differences are nullified by x-ray irradiation of all the synthetic quartz except one which contains germanium. The effect of x-ray irradiation can be removed by thermal bleaching at temperatures between 200 and 500 deg C for a few hours. The thermal-bleaching temperature is different for different types of quartz. (auth)