White Quartz Research Articles

Choosing the site, getting the stones, building the dolmens: local sourcing of andesites at the El Pozuelo megalithic complex (Huelva, Spain)

The geoarchaeological study focuses on the lithological characterization and provenance determination of the rocks of the El Pozuelo dolmens. The difficulty of identifying volcanic rocks in the intensely altered and deformed environment of the Iberian Pyrite Belt has required the implementation of a research methodology combining the archaeological and geological analysis of the megaliths and the area surrounding the Los Llanetes group. A total of 29 thin sections and 14 geochemical analyses (ICP-AES, ICP-MS and REE) have been carried out on samples from the dolmens and potential source areas, focusing on the chemical elements considered immobile during alteration processes. The petrological analyses confirm the identification of different andesite lithotypes and enable us to correlate the rocks used in the construction of the megaliths with source areas and quarries located within a 50–350 m radius. Several patterns are observed in the selection of the rocks, based on the material, visual and symbolic properties of the different lithologies. Foliated andesite is the most common stone used in the monuments, due to its excellent physical properties and technological suitability for extraction and transformation into megalithic supports. Other types of andesite (sheared, massive and amphibole-phyric), white quartz, ferruginous agglomerate and gabbro were also used for different architectural purposes. The results confirm the importance of locally available suitable rocks in determining site location, raw material procurement and monument construction during the Late Neolithic.

Genesis of the Fenghuangshan gold deposit, eastern Hebei, China: Insights from ore geology, fluid inclusion and H–O–S isotopes

The Jidong area is a vital gold province in North China, including plenty of metamorphic rock-hosted gold deposits. Whether ore-forming fluids are magmatic or metamorphic remains controversial. The genesis for gold mineralization in this gold province is ambiguous. The Fenghuangshan gold deposit lies on the eastern fragment of the Jidong gold province. In this paper, we present a detailed study on ore geology, fluid inclusions, and stable isotopes for the deposit to illustrate the characteristics of ore-forming fluids and ore genesis.The deposit occurs as gold-bearing quartz vein and disseminated- and veinlet-type mineralization. The main orebody named 7# is hosted in migmatitic granite, controlled by NE trending secondary fracture system. Four hydrothermal mineralization stages were identified, including: (Ⅰ) white quartz, (II) pyrite-quartz, (III) quartz-polymetallic sulfide, and (IV) calcite-chlorite-quartz. The Stage II and III belong to main gold mineralization stage. Fluid inclusions from different stages show that a lowering trend of fluid inclusion homogenization temperature was observed. They ranged from 222 °C to 407 °C (early-stage), 144 °C to 375 °C (main-stage), and 86 °C to 174 °C (late-stage), respectively. The salinities of the ore-forming fluids were typically low, ranging from 0.83 to 15.47 wt% NaCl equivalent. On the basis of Laser Raman analysis and fluid inclusion microthermometry, the ore-forming fluids belonged to a low- to moderate-temperature, low-salinity H2O-NaCl-CO2 system. Fluid immiscibility gave rise to rapid gold deposition. The early-stage δD and δ18OH2O values from quartzs ranged from –96.4‰ to –92.5‰ and from 1.74‰ to 2.44‰, whereas main-stage fluids had δ18OH2O values of –4.10‰ to –3.50‰ and δD values of –91.5‰ to –89.5‰. The early- and main-stage sulfide δ34S values varied from –2.0‰ to + 2.2‰, with average values of + 0.4‰. H-O-S-isotope data indicated that the primary ore-forming fluids were magmatic water mixing meteoric water during mineralization, and ore-forming materials were derived from a homogeneous magmatic source. Ore geology, fluid inclusions, and stable isotopes illustrate that the Fenghuangshan gold deposit is a low- to moderate-temperature magmatic-hydrothermal gold deposit. Future deep-seated and surrounding gold exploration should center on this area.

A Permian intermediate-sulfidation epithermal Pb–Zn–Ag deposit in the northern margin of North China Craton

Recent Pb–Zn–Ag exploration in the northern margin of North China Craton has made significant new discoveries. Here we report one Pb–Zn–Ag deposit in the Shaolanghe orefield with typical signatures of intermediate-sulfidation epithermal deposits. Zhangjiagou Pb–Zn–Ag mineralization occurs within the Early Permian quartz diorite and Late Permian andesite. Three mineralization stages were identified: white quartz–rhodochrosite–sulfide Pb–Zn–mineralization stage (I), smoky quartz–sulfide Pb–Zn–Ag–mineralization stage (II), and calcite–quartz non–mineralization stage (III). Four sphalerite samples yield the Rb–Sr age of 265.3 Ma, indicating that Pb–Zn–Ag mineralization was associated with the Late Permian andesite. The liquid-rich fluid inclusions of Stage I show low–medium temperatures of 190–270 °C and low salinities (1–3 wt%), and those of Stage III are slightly lower (190–250 °C, 0.5–2 wt%), suggesting a low-salinity, low-temperature H2O–NaCl fluid system for the Zhangjiagou deposit. The H–O–C isotopic signatures indicate a mixed fluid of magmatic water with meteoric water. S and Pb isotopes suggest magmatic source for Zhangjiagou Pb–Zn–Ag mineralization, most likely shallow hydrous intermediate magma. Collectively, these geological, geochronological, and geochemical features indicate that Zhangjiagou is an intermediate-sulfidation epithermal Pb–Zn–Ag deposit.

Pseudo-Karst Silicification Related to Late Ni Reworking in New Caledonia

Silicification in New Caledonian pseudo-karsts developed on peridotite was assessed using δ18O and δ30Si pairs on quartz cements. The objective was to document the chronology of pseudo-karst development and cementation relative to geomorphic evolution. The latter began at the end of the Eocene with the supergene alteration of peridotites and the subsequent formation of extended lateritic weathering profiles. Neogene uplift favoured the dismantling of these early lateritic profiles and valley deepening. The river incision resulted in (i) the stepping of a series of lateritic paleo-landforms and (ii) the development of a pseudo-karst system with subvertical dissolution pipes preferentially along pre-existing serpentine faults. The local collapse of the pipes formed breccias, which were then cemented by white quartz and Ni-rich talc-like (pimelite). The δ30Si of quartz, ranging between −5‰ and −7‰, are typical of silcretes and close to the minimum values recorded worldwide. The estimated δ18O of −6 to −12‰ for the fluids are lower than those of tropical rainfall typical of present-day and Eocene–Oligocene climates. Evaporation during drier climatic episodes is the main driving force for quartz and pimelite precipitation. The silicification presents similarities with silcretes from Australia, which are considered predominantly middle Miocene in age.

The Paragenetic Stage of the Dongping Gold Deposit in the Northern Margin of the North China Platform

The Dongping gold mine, located at the northern margin of the North China Platform, is one of the few large-scale gold deposits in China related to alkaline complex intrusions. In view of this, in-depth dissection of its causes is not only of geological theoretical significance, but also helps to find more similar gold resources under similar geological background, so as to benefit local people. To achieve the above goals, it is necessary to accurately grasp the paragenetic process of the deposit, that is, its paragenetic period and paragenetic stage. Through detailed field and laboratory research, the authors of this paper concluded that the formation of the Dongping gold deposit was the result of multi-stage paragenetic process. Specifically, the formation of the Dongping gold deposit has gone through the following four paragenetic stages, namely (from early to late): Milky white quartz (Q1)-potassium feldspar (K1)-coarse grained pyrite (cgPy) stage, Grey white quartz (Q2)-brick-red potassium feldspar (K2) stage, Potassium feldspar (K3)-quartz (Q3)-polymetallic sulfide stage, and Calcite-chert (Q4)-barite stage. Among them, the third stage, that is, the Potassium feldspar (K3)-quartz (Q3)-polymetallic sulfide stage, is the most important paragenetic stage, marking the climax of the gold mineralization of the deposit.

Breccia and vein mineralization of the Balatoc Diatreme, Acupan gold deposit, Baguio Mineral District: An example of a diatreme-hosted epithermal deposit in the Philippines

The Acupan epithermal gold deposit is one of the Philippines’ largest gold camps, having produced over 200 t Au in the last century with average grades of ∼ 6 g/t Au mostly from well-studied vein orebodies hosted by the Virac Granodiorite. However, vein and breccia mineralization (90/99 veins and GW orebodies, respectively) currently being mined in the northeastern portion of the Acupan deposit is hosted by the less-studied Balatoc Diatreme. This study demonstrates the role of the diatreme as a precursor to epithermal mineralization at Acupan, providing structural control in focusing the fluid flow along the diatreme margin. Mineralization in the Balatoc Diatreme formed across five mineralization stages. Stage I, the main gold mineralization stage, is characterized by gray quartz with pyrite + marcasite + arsenopyrite + electrum + sphalerite ± chalcopyrite. Stage II is typified by white quartz associated with pyrite + electrum + chalcopyrite. Stage III, a newly recognized stage for the Acupan gold deposit, is composed of clear quartz hosting pyrite + stibnite + chalcopyrite + galena + sphalerite + electrum (±pyrite + marcasite + arsenopyrite). Stage IV and Stage V are associated with calcite and gypsum, respectively, hosting trace amounts of pyrite and sphalerite.Fluid inclusions hosted by Stage I and Stage II vein quartz revealed homogenization temperatures (Th) ranging from 220 to 230 °C and 280 to 290 °C, respectively. The fluid inclusions in Stage III quartz breccia cement recorded bimodal homogenization temperatures, 230 to 240 °C and 280 to 290 °C. Fluid inclusion and textural evidence from Stage I quartz and Stage II quartz suggest boiling conditions during ore formation of veins transecting the Balatoc Diatreme. Fluid mixing, on the other hand, is proposed for the formation of the base-metal rich Stage III mineralization of the GW orebodies quartz cement. Pyrite and sphalerite δ34S values (0.8 to 1.5 ‰) from Stage I to Stage IV veins and breccias indicate reduced ore-forming conditions in an H2S-dominated system. Meanwhile, the negative δ34S values (−1.6 to −1.5‰) measured from the pyrite of Stage V breccia, first reported in this study, imply partitioning of the heavier isotopes to the gypsum sulfate in an oxidizing environment and suggest possible spatial variations of sulfur isotope signatures across the Acupan epithermal vein system. This study emphasizes the significance of fluid mixing in diatreme-hosted epithermal deposits such as Acupan. The diatreme possibly provided pathways between the contrasting magmatic-hydrothermal and meteoric environments, resulting in ore precipitation.

Fluid inclusion and isotopic constraints on the origin of the Ag-Pb-Zn polymetallic mineralization at Biliya, Great Xingan Range, NE China

The Biliya Ag-Pb-Zn polymetallic (SLZP) deposit (16.5 Mt, @ 52.9 g/t Ag, 2.6% Pb and 2.3% Zn) lies in the Great Xing’an Range, Northeast China. Breccia-, veinlet- and vein-type Ag-Pb-Zn ore bodies are primarily hosted in the quartz porphyry, trachyandesite and rhyolitic tuff. They are spatially and temporally related to andesitic porphyry. Three mineralization processes are identified: stage I: grey quartz - pyrite + tawny sphalerite (high Cd2+), stage II: grayish white quartz - pyrite + grey sphalerite (high Fe2+) + galena + argentite + tetrahedrite, stage III: white quartz-pyrite. The alterations consist of quartz + sericite, illite + quartz, fluorite + calcite + opal and chlorite zone. The silver-lead–zinc mineralization primarily corresponds to stage II. Five sulfide samples from stage II yielded a well-fitted isochron age of 131.3 ± 2.4 Ma (MSWD = 2.4), marking the timing of Ag-Pb-Zn polymetallic mineralization. CO2-bearing NaCl-H2O (C), gaseous CO2 (V); vapour-liquid H2O-NaCl (WL) and fluid-phase H2O-NaCl (L)-type of fluid inclusions were distinguished. Their petrographic and microthermometric features and H-O isotopic data suggest that the hydrothermal fluids were initially originated from magmatic source, with intensive mixing with meteoric water and that their temperatures and salinities are 254–130 ℃ and 7.15–1.22 wt% NaCl eqv, respectively, belonging to a reduced fluid (CO2-H2O-NaCl ± CH4) system. In-situ S and bulk Pb isotope analyses indicate that the metal materials were related to andesitic magma from the lower crust. The deposit geology, fluid inclusions, stable isotopes and chronology results suggest that the Biliya deposit belongs to a low-sulfidation (LS) epithermal SLPZ deposit. Boiling and fluid immiscibility coupled with suddenly decreasing in temperature, pressure, logfS2 of the hydrothermal fluids are likely to play important roles in Biliya SLPZ ore deposition.

Industrial White Quartz Stone Classification Using Image Processing and Supervised Learning

A vision-based stone classifying method was developed for industrial mine stone grading applications. The image-based solution is used to extract visual parameters and stones are classified by their color and shape parameters with the help of the machine learning algorithms. In the experiments, four groups, each including ten arbitrarily selected stones; in total forty stone samples with complex colors and shapes were examined. Four different images are captured under four different angles and processed to extract visual parameters of each stone sample. In training stage 67% of the data were used for training and rest were used for testing process. The method correctly classifies mine stones up to 98% from still images using labeled inputs. A confusion matrix derived from the experimental results is employed in order to emphasize the efficiency of the system more clearly and emphasize the results in a certain manner.

Use of White Quartz Sand for High-Strength Concrete

Use of White Quartz Sand for High-Strength Concrete

Host Range, Biology, and Factors Affecting Survival and Reproduction of the Stubby Root Nematode

Populations of T. allius increased to levels nine times higher in Glurk tobacco plants infected with California tobacco rattle virus than in healthy plants of the same variety and age. Populations of T. christiei increased with applications of Hoagland's nutrient solution diluted up to 50-percent concentration, whereas population densities were low at the highest concentration (100 percent), and in water alone. Trichodorus allius did not seem to be affected to a large extent by similar applications of Hoagland's nutrient solution. Soil type influenced populations of T. allius; lighter soils were conducive to development of higher populations while soil, coarse sand, and white quartz sand used separately were not favorable for reproduction. Temperature proved to be one of the most important ecological factors in nematode reproduction. The optimum temperatures for the reproduction of each species was as follows: T. christiei, 16° to 24° C; T. porosus, 24° C; and. T allius, 21° to 24° C. Extremes of temperatures at which the different species could reproduce also varied. Populations of T. christiei were affected by an undetermined disease or condition which seemed to slow movement but did not have any apparent effect on rate of reproduction. Host ranges of three species of Trichodorus were studied. All three nematode species seemed to be polyphagous because 90 percent, 90 percent and 95 percent of the plant species tested were hosts of T. christiei, T. porosus, and T. allius, respectively. Twenty-five plant species were tested for T. porosus, 50 for T. christiei and 38 for T. allius. A method is described for keeping populations of T. allius alive in water for extended periods of time.

Genesis of Gold Deposit in Um Trambishi Area, NE Atbara, Sudan.

Um Trambishi area consists of volcano-sedimentary sequence intruded by syntectonic pluton of granitoids composition with marginal fissures injected by aplite, had been subjected to dynamic metamorphism and obliterated by recrystallization forming different rock units varying in composition, forming greenschist terrains. These are an assemblage of recrystalline schists, meta-acid, cataclastic tonalite, granodiorites, meta-andesite, chlorite schists, quartzite, marble, metabanded chert, together with two generations of unmineralized deformed and undeformed white quartz, which are oriented mainly in E-W and N-S direction following faults trend. The area is subjected to four deformational phases of brittle-ductile transition. The metamorphic grade is Green Schist Facies. The alteration around the endo-contact zone is characterized by minerals: albite, chlorite, epidote, sericite, carbonate and kaolin with anomalous Au=0.91ppm, Ag=1.75ppm, As=44.6XRF, Co=15.70XRF, V=65XRF, Ti=4796XRF, Cr=23XRF, Sr=269XRF, and base metals Pb=1.51ppm, Zn=22.02ppm and Cu=13.59ppm. The first phase of hydrothermal solution carrying gold is related to the magmatic high temperature associated with granitoidal intrusions, deposited into the planar fabric S1 and has a characteristic signature of hypothermal processes .The second mode of occurrence is the regeneration of auriferous quartz stringers filling into the tectonic fissures trending 340⁰ and oblique to S1 as a result of D3 (Keraf Shear Zone) and has a characteristic signature of mesothermal processes.

Discovery of agate geode and nodules at Mount Conner, Semporna, Sabah

An exposure of agate geode and nodules in Mount Conner, Sabah, provides an essential aspect to the geological formation in Semporna. This paper briefly report results from petrography analyses on the agate geode and nodules and its significance to the volcanic rocks and sedimentary rocks formation in Mount Conner. The geode and nodules can be divided into agate, and nodules and most of them are sub-rounded. Nodules are usually small in size and display brownish colour. It commonly occurs in volcanic rocks (dacite and rhyolite) and contained amygdale filled by secondary mineral such as microcrystalline and macrocystalline quartz. In contrast, sedimentary rocks in Mount Conner contain both nodules and geodes, which nodules shows similar characteristic with nodules in volcanic rocks and geodes contained empty vesicles or spaces surrounded by colourless to milky white quartz crystals. Both geode and nodules exhibit conchoidal fracture, while geode shows vesicle features and nodules in volcanic rocks show amygdale texture. The formation of geodes and nodules in Mount Conner might as result of precipitation under low temperature from hydrothermal solution.

Classification of the Paleoproterozoic Gulcheru Formation: Implications on Early Paleogeographic and Tectonic Evolution of the Cuddapah Basin, India

Abstract The Papaghni sub-basin of the Cuddapah basin is an arcuate NW-SE trending intracratonic basin, stretching from Kurnool in the NW to Guvvalacheruvu in the SE, in southern peninsular India. Despite of large number of researches, an understanding of the evolution of the basin is still elusive. The sub-basin preserves records of repeated opening and closing of Paleoproterozoic rifts along the zone of NW-SE trending axis in the East Dharwar craton. Present study was carried out along the southwestern margin of the Papaghni sub-basin, in and around Tadpatri-Gooty-Dhone area, where the successive litho-units are represented by two major unconformity-bound sequences. Each of these sequences are characterized by a distinctive set of litho-assemblage, deposited under diverse tectonic environments with highly variable modes and tempos of sedimentation in an extensional basin. The basin initiated at about 2 Ga and shortly evolved into a shallow sea, with development of wide siliciclastic shelf in an open marine condition, the Gulcheru Formation. Gradually, with time the siliciclastic shelf was replaced by an extensive stromatolitic carbonate platform, the Vempalle Formation. Dedicated fieldwork exemplifies that the initial basin-fill is characterized largely by several cycles of simple, but amalgamated and stacked fanglomerates (alluvial fan to fan-delta) systems developed from several single stream breaches onto the proximal setting of the basin, in a syn-rift setting. These fanglomerates display a fining upward sequence, which progressively passes up to high-energy coastal, tide-storm dominated shelf environments of post-rift setting. This study justifies the subdivision of the Gulcheru Formation into two formal lithostratigraphic members, the Daditota Member and the Karvipalle Member. The Daditota Member directly overlies the granitoid basement and grades upward to Karvipalle Member. Karvipalle Member, comprising predominantly of medium to fine-grained, reddish brown and white quartz arenites of stable shelf deposits, distinctly differs from the conglomerate and very coarse-grained mass-flow dominated deposits of the Daditota Member. The Vempalle Formation overlies the Gulcheru Formation with a gradational contact and consists of stromatolitic dolomite, oolite and shale, developed in a ramp type carbonate platform setting. Gradual transition from siliciclastic to carbonate sequence points to passive margin setting developed during the breakup of the supercontinent Kenorland. Disposition of proximal to distal sequences and northeastern, eastern and southeastern paleocurrent of the sequences advocate a NW-SE shoreline and eastern paleo-slope of the basin.

Silicate-, Magnesium Ion-, and Urea-Induced Prebiotic Phosphorylation of Uridine via Pyrophosphate; Revisiting the Hot Drying Water Pool Scenario.

The availability of nucleotides on the early Earth is of great significance for the origin of a self-replicating system capable of undergoing evolution. We hereby report the successful phosphorylation reactions of the nucleoside uridine under heating in the “drying pool” prebiotic model at temperatures ranging from 60–75 °C, and by using pyrophosphate as a phosphorylation agent. Uridine monophosphates (UMP) such as uridine-5′-monophosphate (5′-UMP), 2′-UMP, and 3′-UMP, as well as cyclic 2′-3′-UMP, were identified by 31P-NMR. In addition to the above-mentioned products, a dimer of uridine-phosphate-uridine (U-P-U) was also observed. The reactions were promoted by white quartz sand, Mg2+, and by using urea as a condensation agent. The reactions also proceeded without this mixture; however, the yields increased remarkably with the presence of the above-mentioned materials. The results suggest that a hot/evaporating-drying pool of water containing organics, salts, and reactive phosphorus could be sufficient to form significant phosphate esters.

ВЛИЯНИЕ ДОБАВОК ZnO и BaSO4 НА СТРОИТЕЛЬНО-ТЕХНИЧЕСКИЕ СВОЙСТВА НИЗКООСНОВНЫХ БЕЛЫХ ЦЕМЕНТОВ

white cement – modern construction material which is increasingly popular every year as it is used not only in the construction sphere, but also and in creation of architectural products.
 Today the most famous producers of white cement is Turkey, Denmark and Egypt. Special color of cement is reached due to specific structure and the specialized production technology. Clinker for the white portlandtsement, differs from usual in the increased maintenance of Si2O (23.5-25.5%) and A12O3 (5.5-7%), insignificant quantity of Fe2O3 (up to 0.25-0.35%) and MnO – 0.05-0.15%. The mineral composition of clinker for white cements fluctuates within (%): C3S – 35-50; 35-45; C3A 14-17; C4AF 0.9-1.4. The maintenance of MgO in it should not exceed 4.5%. For production of the white portlandtsement the cleanest kinds of carbonate and sandy-argillaceous raw materials are used. In particular, the straight limestones or chalk containing no more than 0.15% of the painting oxides are applied. The kaolin, waste of its enrichment and other materials are served as a clay component. The fine-grained white quartz sands, waste of quartz sand received at enrichment of a kaolin, etc. to increase in the silicate module are applied.
 The ashless fuel which is not forming soot and ashes that helps to avoid pollution is applied to roasting of clinker. Crushing of raw materials is carried out in special mills, and crushing is carried out by means of silicon or porcelain elements. Such production technology helps to achieve the grinding having higher rates than from traditional cements.
 Results of a research of influence of mineral BaSO4 and ZnO additives on synthesis and properties of the low-main clinker of the white portlandtsement are given in work: clinker formation, hydration activity, whiteness of cement.

Boy Discovered in Suitcase, and: Pastoral, and: Sonnet

Boy Discovered in Suitcase, and: Pastoral, and: Sonnet Karl Kirchwey (bio) BOY DISCOVERED IN SUITCASE (luggage scan photograph, The New York Times, May 20, 2015) You say the state was already broken when he fellout of his mother's body into time.You say it was mobile phones and machetes and dust.But here he is, a sonogram, a shadow in a hard case,or 500 dollars for a square meter in a rubber raft,or he slept in a wheel well seven miles high,and you put the dream there, beyond the Pillars of Hercules,that somewhere there is a frontier of slatted steelto comb him from the nightmare of what is happening.He is wrung through every gap in your attention,unsleeping at your sunset gates. The hunched idolof all you took for granted is unlimbering.There are translators who will help him across. [End Page 320] PASTORAL My children have crowned me the great-headed king of the Alps. I adore them, who are slender and alive. I lick their sleeve. They have garlanded my brow with flowers gathered from the June meadow, all that they can hold in one palm: anemone, globeflower, forget-menot, also the night-blue gentian. In homage they bellow like Brown Swiss, while I stand on the one ribbed shield of old snow left in the lee of a mountain that fell long ago, buried a village and made a pristine lake. The marmots whistle from their burrows at my passage up to the sun. I look down at the dark chalet where I lay once in my other body. It has been closed for years: morning glory twines round the shutter. The names of the mountains I knew are leaving me now, Grand Muveran, Petit Muveran, Dents de Morcles, with no more substance than wraiths of cloud that flee [End Page 321] past the wall canted up from an ancient sea, raising its coiled ammonites into the sky. The hollow bronze music of ruminants sounds at this distance like gamelans from a country I will never visit. The lines of white quartz wander in schist lying broken at my feet. I no longer try to understand what is written there: it lies in the retreat of the glacier from its own moraine, the syllable dropped from a word in dialect. My children stand like gilded plants in a valley at dawn. Overhead, the marrow-eating vulture surges, drops and salutes me with a tip of its wing. [End Page 322] SONNET (Acqualoreto, Umbria) 1.The old man says with pride that he spent the morning pickingcherries from his own trees. They overflow the wicker basket at alunch held in his honor, where he moves perfectly at ease. 2.His daughter tells me he is much preoccupied with thoughts ofdeath. 3.Later we are driving a winding road upward to look at a medievaltower bought by some Americans not long ago. There is wildgeranium beside the road, and the fields are dotted with crimsonpoppies. He turns to me and says 4.—There ought to be religion without faith. 5.His mind has a lizard quickness, like the lizard I once saw on asunny wall, its back emerald and its limbs azure, that fell and thenquickly recovered. 6.I feel the drag of language, the gap and delay in my responsewhile a soul waits. I say 7.—Faith makes atrocities, yes. But people cannot live without faith.Without faith, religion is just an intellectual abstraction. 8He looks at me, his face shrewd in the light of yellow broom, andsays [End Page 323] 9.—Are you a believer? The Resurrection was never literal, butrather a promise that, whatever our anguish, Christ can be presentand console us. 10.I do not answer his question. I say 11.—The artists who made the Resurrection literal have given usincomparable solace. 12.And then we have arrived, and the moment closes. He directsmy attention to a plaque commemorating a partisan killed in theSecond World War. 13.The intimacy, the exposure. I do not know where it came from. Or...

The genesis of gold deposits in the Hetai goldfield, South China: New constraints from geochronology, fluid inclusion, and multiple isotopic studies

The Hetai goldfield is one of the largest gold mining districts in the South China Block. A complex paragenesis consists of three mineralization stages: syntectonic metamorphic stage, hydrothermal stage, and supergene stage. The syntectonic metamorphic stage is characterized by banded quartz (Q1) and invisible Au in mylonites. The hydrothermal stage, which is the main gold mineralization stage, can be divided into three substages: an early substage characterized by coarse‐grained quartz (Q2) + pyrite + arsenopyrite + pyrrhotite, an intermediate substage characterized by gray fine‐grained quartz (Q3) + electrum + poly‐sulphides + sericite + chlorite and a late substage with predominate white quartz (Q4) + calcite as well as lesser sulphides. During the supergene stage, malachite, covellite, and limonite were formed. Four types of fluid inclusions (FIs) in these types of quartz were identified: aqueous FIs (type 1), CO2‐bearing aqueous FIs (type 2), CO2‐rich FIs (type 3), and solid‐bearing FIs (type 4). Q1 only contains type 1 FIs; Q2 contains types 2 and 4 FIs; Q3 contains types 2 and 3 FIs; and Q4 only contains type 1 FIs. Microthermometric results show that the homogenization temperatures of fluid inclusions range from 350°C to 400°C for Q1, 250°C to 320°C for Q2, 138°C to 245°C for Q3, and 110°C to 207°C for Q4. Salinities of fluid inclusions range from 3.4 to 5.7 wt.%, 2.6 to 12.9 wt.%, 0.5 to 11.5 wt.%, and 0.2 to 7.3 wt.% for Q1, Q2, Q3, and Q4, respectively. Alteration minerals (sericite and chlorite) from the main mineralization stage have δDH2O‐VSMOW values of −62‰ to −98‰ and calculated δ18OH2O‐VSMOW values of 6.3‰ to 4.4‰. The in situ sulphur isotope analysis of pyrite yields a narrow δ34SCDTrange of −1.5‰ to −5.2‰ (average −3.4‰), combined with the Pb isotopic compositions of the sulphides, wall rocks, and Wucun pluton, revealing that the ore‐forming material was mainly derived from magmatic source. The mineralization age (sericite40Ar/39Ar: 159.3 ± 0.8 Ma) is close to the emplacement age of Wucun biotite monzonitic granite pluton (LA‐ICP‐MS zircon U–Pb age: 158.1 ± 1.9 Ma). These geochemical and geochronological data suggest that the main phase of gold mineralization in the Hetai goldfield is genetically related to the granitic activities in the Late Jurassic rather than the mylonitization event in the Late Triassic to Early Jurassic.

Ore Genesis and Tectonic Significance of the Xiaojiashan Tungsten Deposit, Eastern Tianshan, Xinjiang, China: Evidence from Geology, Fluid Inclusions, and Stable Isotope Geochemistry

AbstractThe Xiaojiashan tungsten deposit is located about 200 km northwest of Hami City, the Eastern Tianshan orogenic belt, Xinjiang, northwestern China, and is a quartz vein‐type tungsten deposit. Combined fluid inclusion microthermometry, host rock geochemistry, and H–O isotopic compositions are used to constrain the ore genesis and tectonic setting of the Xiaojiashan tungsten deposit. The orebodies occur in granite intrusions adjacent to the metamorphic crystal tuff, which consists of the second lithological section of the first Sub‐Formation of the Dananhu Formation (D2d 12). Biotite granite is the most widely distributed intrusive bodies in the Xiaojiashan tungsten deposit. Altered diorite and metamorphic crystal tuff are the main surrounding rocks. The granite belongs to peraluminous A‐type granite with high potassic calc‐alkaline series, and all rocks show light Rare Earth Element (REE)‐enriched patterns. The trace element characters suggest that crystallization differentiation might even occur in the diagenetic process. The granite belongs to postcollisional extension granite, and the rocks formed in an extensional tectonic environment, which might result from magma activity in such an extensional tectonic environment. Tungsten‐bearing quartz veins are divided into gray quartz vein and white quartz veins. Based on petrography observation, fluid inclusions in both kinds of vein quartz are mainly aqueous inclusions. Microthermometry shows that gray quartz veins have 143–354°C of Th, and white quartz veins have 154–312°C of Th. The laser‐Raman test shows that CO2 is found in fluid inclusions of the tungsten‐bearing quartz veins. Quadrupole mass spectrometry reveals that fluid inclusions contain major vapor‐phase contents of CO2, H2O. Meanwhile, fluid inclusions contain major liquid‐phase contents of Cl−, Na+. It can be speculated that the ore‐forming fluid of the Xiaojiashan tungsten deposit is characterized by an H2O–CO2, low salinity, and H2O–CO2–NaCl system. The range of hydrogen and oxygen isotope compositions indicated that the ore‐forming fluids of the tungsten deposit were mainly magmatic water. The ore‐forming age of the Xiaojiashan deposit should to be ~227 Ma. During the ore‐forming process, the magmatic water had separated from magmatic intrusions, and the ore‐bearing complex was taken to a portion where tungsten‐bearing ores could be mineralized. The magmatic fluid was mixed by meteoric water in the late stage.

Ore-bearing fluids of the Eldorado gold deposit (Yenisei Ridge, Russia)

The Eldorado low-sulfide gold-quartz deposit, with gold reserves of more than 60 tons, is located in the damage zone of the Ishimba Fault in the Yenisei Ridge and is hosted by Riphean epidote-amphibolite metamorphic rocks (Sukhoi Pit Group). Orebodies occur in four roughly parallel heavily fractured zones where rocks were subject to metamorphism under stress and heat impacts. They consist of sulfide-bearing schists with veins of gray or milky-white quartz varieties. Gray quartz predominating in gold-bearing orebodies contains graphite and amorphous carbon identified by Raman spectroscopy; the contents of gold and amorphous carbon are in positive correlation. As inferred from thermobarometry, gas chromatography, gas chromatography-mass spectrometry, and Raman spectroscopy of fluid inclusions in sulfides, carbonates, and gray and white quartz, gold mineralization formed under the effect of reduced H2O-CO2-HC fluids with temperatures of 180 to 490 °C, salinity of 9 to 22 wt.% NaCl equiv, and pressures of 0.1 to 2.3 kbar. Judging by the presence of 11% mantle helium (3He) in fluid inclusions from quartz and the sulfur isotope composition (7.1-17.4‰ δ34S) of sulfides, ore-bearing fluids ascended from a mantle source along shear zones, where they “boiled”. While the fluids were ascending, the metalliferous S- and N-bearing hydrocarbon (HC) compounds they carried broke down to produce crystalline sulfides, gold, and disseminated graphite and amorphous carbon (the latter imparts the gray color to quartz). Barren veins of milky-white quartz formed from oxidized mainly aqueous fluids with a salinity of <15 wt.% NaCl equiv at 150-350 °C. Chloride brines (>30 wt.% NaCl equiv) at 150-260 °C impregnated the gold-bearing quartz veins and produced the lower strata of the hydrothermal-granitoid section. The gold mineralization (795-710 Ma) was roughly coeval to local high-temperature stress metamorphism (836-745 Ma) and intrusion of the Kalama multiphase complex (880-752 Ma).

Optical coefficients extraction from terahertz time-domain transmission spectra based on multibeam interference principle

We demonstrated a data-processing method based on multiple beam interference and Fresnel equations that simultaneously gave the refraction index and absorption coefficient from the raw data of terahertz (THz) time-domain spectroscopy (TDS), which laid the foundation for obtaining the dielectric parameters. This method was independent of phase processing, and complete material information was reserved without having to cut the time-domain signal. The optical coefficients including refractive indices and absorption coefficients of white polyethylene and quartz samples at different thicknesses were obtained. The applicability and accuracy of this method were discussed and verified by comparison with the traditional data-processing method of THz TDS.