scholarly journals The Genesis of the Giant Shuangjianzishan Epithermal Ag-Pb-Zn Deposit, Inner Mongolia, Northeastern China

2020 ◽  
Vol 115 (1) ◽  
pp. 101-128 ◽  
Author(s):  
Degao Zhai ◽  
Anthony E. Williams-Jones ◽  
Jiajun Liu ◽  
David Selby ◽  
Panagiotis C. Voudouris ◽  
...  
Keyword(s):  
Ore Deposits ◽  
Northeastern China ◽  
Granite Porphyry ◽  
Time Interval ◽  
Short Time Interval ◽  
Sulfur Source ◽  
Weighted Mean ◽  
Ore Minerals ◽  
Porphyry Intrusion

Abstract The newly discovered Shuangjianzishan Ag-Pb-Zn deposit, with 145 Mt of ore grading 128.5 g/t Ag (locally up to 32,000 g/t) and 2.2 wt % Pb + Zn, is located in the Great Hinggan Range metallogenic belt, northeastern China, and is currently the largest Ag deposit in Asia. The Ag-Pb-Zn orebodies occur as veins and are hosted primarily by a Permian slate. Recent drilling and core logging have identified a partially Mo mineralized granite porphyry intrusion adjacent to the Ag-Pb-Zn mineralized veins. This well-preserved magmatic-hydrothermal system therefore offers an excellent opportunity to evaluate the possible temporal and genetic relationship between Mo-mineralized porphyry intrusions and Ag-Pb-Zn veins. Three primary paragenetic stages of veining have been recognized: (I) early pyrite + quartz ± K-feldspar, (II) main ore sulfide + sulfosalt + quartz + calcite + sericite + chlorite ± epidote, and (III) post-ore quartz. The silver mineralization occurs mainly in the late paragenetic part of Stage II, in which canfieldite (Ag8SnS6), argentite (Ag2S) and freibergite [(Ag, Cu)12Sb4S13] are the dominant Ag-bearing ore minerals. A combination of ore mineral chemical and sulfur isotope geothermometers and physicochemical calculations suggest that the Ag-Pb-Zn mineralization took place at a temperature of 250° to 200°C, a pH of 6.7 to 5.6, and a Δlogfo2 (HM) of –2.4 to –8.7. A conspicuous enrichment of Sn and Se in the ore, which is represented by minerals containing the metal suite Ag-Pb-Zn-(Cu-Sn-Se-Sb), likely reflects a close genetic association between the base metal mineralization and a magma. In situ analyses show that the δ34S values of the sulfides and Ag-bearing sulfosalts from the Ag-Pb-Zn mineralized veins vary from –4.67 to +2.44‰; the mean value is –2.11 ± 1.49‰ (n = 77). The calculated mean δ34SH2S value of the ore-forming fluid is –1.65 ± 0.83‰, which is indicative of a magmatic sulfur source. In situ Pb isotope analyses of the ore minerals yielded a narrow range of values (206Pb/204Pb of 18.243–18.310, 207Pb/204Pb of 15.503–15.563 and 208Pb/204Pb of 38.053–38.203, n = 59). Comparisons to corresponding isotopic data for the various rock units in the area and sulfides from nearby ore deposits indicate that there were substantial contributions of Pb and other metals (e.g., Ag and Zn) to the Shuangjianzishan deposit from a Mesozoic granitic source. Diorite-granodiorite dikes and dacite are crosscut by the Ag-Pb-Zn veins, and therefore, predate ore formation. These rock units have zircon U-Pb ages of 250.2 ± 2.0 and 133.9 ± 1.4 Ma, respectively. A concealed, weakly Mo mineralized granite porphyry intrusion proximal to the Ag-Pb-Zn mineralized vein system yielded zircon U-Pb ages of 134.4 ± 1.0 (MSWD = 0.1) and 134.4 ± 1.0 Ma (MSWD = 0.2), for coarse- and fine-grained facies, respectively. These ages are indistinguishable within the uncertainty from the zircon ages for the dacite and a granite intrusion ~2 km north of the mineralized veins, which has a weighted mean zircon U-Pb age of 135.2 ± 1.4 Ma (MSWD = 0.78). Molybdenite from three quartz vein/veinlet samples hosted by slate immediately above the porphyry intrusion yielded Re-Os model ages from 136.3 ± 0.9 to 133.7 ± 1.2 Ma and a weighted mean Re-Os age of 134.9 ± 3.4 Ma. Finally, three pyrite samples separated from the Ag-Pb-Zn mineralized veins have a weighted mean Re-Os model age of 135.0 ± 0.6 Ma. The very similar zircon U-Pb ages for the Mo-mineralized granite porphyry and dacite, and Re-Os ages for molybdenite and pyrite in the Shuangjianzishan ore district indicate that the Mesozoic magmatic-hydrothermal activity was restricted to a relatively short time interval (~136–133 Ma). They also suggest that the weakly Mo mineralized granite porphyry was likely the source of the fluids and metals that produced the Ag-Pb-Zn mineralization. Based on our geological observations and an extensive analytical database, a model is proposed for the genesis of the giant Shuangjianzishan Ag-Pb-Zn deposit in which the ore-forming fluid and its metals (i.e., Ag, Pb, and Zn) were exsolved during crystallization of the final phase of a composite granite porphyry intrusion. This fluid transported metals to the distal parts of the system, where they were deposited in preexisting faults or fractures created by the withdrawal of magma during the waning stages of the magmatic-hydrothermal event. The present study of the Shuangjianzishan Ag-Pb-Zn deposit and those of other magmatic-hydrothermal ore deposits in the region provide compelling evidence that the widespread Mesozoic felsic magmatism and Ag-Pb-Zn mineralization in the southern Great Hinggan Range took place in an intracontinental extensional tectonic setting, which was synchronous with, and spatially associated to, Paleo-Pacific slab rollback and lithospheric delamination and thinning.

scholarly journals EPITHERMAL MANGANESE MINERALIZATION, KIMOLOS ISLAND, SOUTH AEGEAN VOLCANIC ARC, GREECE

2017 ◽  
Vol 43 (5) ◽  
pp. 2646 ◽  
Author(s):  
N. Lykakis ◽  
S. P. Kilias
Keyword(s):  
Sea Water ◽  
Metal Sulfide ◽  
Ore Deposits ◽  
Vein Wall ◽  
Volcanic Arc ◽  
Ore Minerals ◽  
Manganese Mineralization ◽  
Element Enrichment ◽  
Low Sulfidation

Manganese mineralization is hosted by a marine monomictic, lithic volcaniclastic breccia, possibly an andesitic in situ hyaloclastite, and shallow-marine or subaerial epiclastic conglomerates, in the Korakies area, NE Kimolos, active south Aegean volcanic arc. Old mine workings (in the form of rubble, adit and shaft), and abandoned rail and ship loading facilities, exist in the area. Mineralization occurs as a quartz/chalcedony vein system filling extensional NNE-SSW–trending faults and fractures, of Pliocene age. Maximum vein width reaches 5 m; length may extend to 250 m. The ore shares strong textural analogies with volcanic-hosted epithermal-style deposits, i.e. crustiform banding, vugs, hydrothermal breccias, cockade and comb textures. Vein wall rocks are hydrothermally altered to quartz-adularia±illite, chlorite and barite. Pyrolusite, hollandite, cryptomelane, and coronadite are the main ore minerals, with quartz, chalcedony, jasper and barite gangue. Ore samples contain up to 25.8 % MnO2, 14.7 % FeOTOT, 2860 ppm Zn, 1132 ppm Pb and 136 ppm Cu; Mn and Zn show mutual positive correlation (r2=0.61). Trace element enrichment (i.e. Zn, Pb, and Cu) may suggest a proximal base metal sulfide mineralization. Concentrations of 4.3 % Na, 0.09 % Mg and barite presence may suggest genetic involvement of sea water. The mineralization studied is similar to volcanic-hosted low-sulfidation epithermal ore deposits deposited from neutral pH fluids. This is a rare example of a vein-type epithermal-style hydrothermal manganese deposit formed in a marine environment.

scholarly journals Halley’S Comet (Part I): Ground-based Observations

1989 ◽  
Vol 8 ◽  
pp. 3-16
Author(s):  
Richard M. West
Keyword(s):  
Space Missions ◽  
In Situ Measurements ◽  
Time Interval ◽  
Short Time Interval ◽  
International Programme ◽  
Halley's Comet ◽  
Large Telescopes ◽  
Short Time ◽  
Comet Halley

AbstractSince the recovery in October 1982, an extensive, international programme to observe Comet Halley with ground-based instruments has been co-ordinated by the International Halley Watch (IHW), and a comprehensive archive is now in the final phases of preparation. The observations were carried out at more than 150 observatories and with all available methods. A special effort was made to support the space missions during the comet encounters in early March 1986. Whereas the spacecraft provided detailed in-situ measurements over a short time interval, ground-based observers have so far followed the development of the comet over a period of nearly six years, and a number of spectacular events near the nucleus and in the tail have been documented in great detail. These observations still continue. This article gives an overview of the most important results obtained from the ground and also mentions the prospects for further observations with large telescopes during the next years.

scholarly journals Estimation of Raindrop Size Distribution Parameters Using Lightning Data over West Sumatra

2021 ◽  
Vol 13 (2) ◽  
pp. 92-100
Author(s):  
Faridah Salma ◽  
Marzuki Marzuki ◽  
Hiroyuki Hashiguchi ◽  
Fadli Nauval
Keyword(s):  
Time Interval ◽  
Short Time Interval ◽  
Time Intervals ◽  
Raindrop Size Distribution ◽  
West Sumatra ◽  
Distribution Parameters ◽  
Raindrop Size ◽  
The Tropics ◽  
Short Time

In situ observations of raindrop size distributions (DSDs) are still limited, especially in the tropics. Therefore, this study develops an alternative method to calculate DSD parameters by utilizing lightning data from the World-Wide Lightning Location Network (WWLLN) observation. DSD data was obtained from Parsivel's observations in the equatorial regions of Indonesia, i.e., Kototabang (100.32◦E, 0.20◦S, 865 m above mean sea level/ASL), Padang (100.46°E, 0.915°S, 200 m ASL), and Sicincin (100.30°E, 0.546°S, 134 m ASL). A gamma distribution parameterized the DSD. Three analysis domains were examined, with a grid of 0.1° x 0.1°, 0.5° x 0.5°, and 1° x 1°.  We examined the possibility to calculate the near-instantaneous DSD parameter, so three short time intervals, namely, one, five and ten minutes, were used. The results showed that the number of lightning strokes does not adequately correlate with DSD parameters. This is observed in all time intervals and analysis domains. Thus, the use of lightning data to calculate DSD parameters is not possible for short time interval of DSD (near instantaneous DSD). However, lightning data can estimate the average DSD parameters for an average time of more than one hour, as recommended by previous studies.

scholarly journals Staged formation of the supergiant Olympic Dam uranium deposit, Australia

Geology ◽  
2021 ◽  
Author(s):  
Kathy Ehrig ◽  
Vadim S. Kamenetsky ◽  
Jocelyn McPhie ◽  
Edeltraud Macmillan ◽  
Jay Thompson ◽  
...  
Keyword(s):  
Uranium Deposit ◽  
South Australia ◽  
Ore Deposits ◽  
Ore Deposit ◽  
Timing Information ◽  
Ore Minerals ◽  
Extreme Metal ◽  
Two Stages ◽  
Olympic Dam

The origins of many supergiant ore deposits remain unresolved because the factors responsible for such extreme metal enrichments are not understood. One factor of critical importance is the timing of mineralization. However, timing information is commonly confounded by the difficulty of dating ore minerals. The world’s largest uranium resource at Olympic Dam, South Australia, is exceptional because the high abundance of U allows U-Pb dating of ore minerals. The Olympic Dam U(-Cu-Au-Ag) ore deposit is hosted in ca. 1.59 Ga rocks, and the consensus has been that the supergiant deposit formed at the same time. We argue that, in fact, two stages of mineralization were involved. Paired in situ U-Pb and trace element analyses of texturally distinct uraninite populations show that the supergiant size and highest-U-grade zones are the result of U addition at 0.7–0.5 Ga, at least one billion years after initial formation. This conclusion is supported by a remarkable clustering of thousands of radiogenic 207Pb/206Pb model ages of Cu sulfide grains at this time. Upgrading of the original ca. 1.59 Ga U deposit to its present size at 0.7–0.5 Ga may have resulted from perturbation of regional fluid flow triggered by global climatic (deglaciation) and tectonic (breakup of Rodinia) events.

scholarly journals Resolving the timescales of magmatic and hydrothermal processes associated with porphyry deposit formation using zircon U-Pb petrochronology

2020 ◽  
Author(s):  
Simon J. E. Large ◽  
Jörn F. Wotzlaw ◽  
Marcel Guillong ◽  
Albrecht von Quadt ◽  
Christoph A. Heinrich
Keyword(s):  
Trace Element ◽  
High Precision ◽  
Magma Reservoir ◽  
Time Interval ◽  
Short Time Interval ◽  
In Situ Techniques ◽  
Porphyry Cu ◽  
Spatially Resolved ◽  
Hydrothermal Processes

Abstract. Understanding the formation of economically important porphyry-Cu-Au deposits requires the knowledge of the magmatic-to-hydrothermal processes that act within the much larger underlying magmatic system and the timescales on which they occur. We apply high-precision zircon geochronology (CA-ID-TIMS) and spatially resolved zircon geochemistry (LA-ICP-MS) to constrain the magmatic evolution of the magma reservoir at the Pliocene Batu Hijau porphyry-Cu-Au deposit. We then use this extensive dataset to assess the accuracy and precision of different U-Pb dating methods of the same zircon crystals. Emplacement of the oldest pre- to syn-ore tonalite (3.736 ± 0.023 Ma) and the youngest tonalite porphyry cutting economic Cu-Au mineralisation (3.646 ± 0.022 Ma) is determined by the youngest zircon grain from each sample, which constrains the duration of metal precipitation to less than 90 ± 32 kyr. Overlapping spectra of single zircon crystallisation ages and their trace element distributions from the pre-, syn and post-ore tonalite porphyries reveal protracted zircon crystallisation together with apatite and plagioclase within the same magma reservoir over > 300 kyr. The presented petrochronological data constrains a protracted early > 200 kyr interval of melt differentiation and cooling within a large heterogeneous magma reservoir leading up to ore formation, followed by magma storage in a highly crystalline state and chemical and thermal stability over several 10s of kyr. Irregular trace element systematics suggest magma recharge or underplating during this final short time interval. The comparison of high precision CA-ID-TIMS results with in-situ U-Pb geochronology data from the same zircon grains allows a comparison of the applicability of each technique as a tool to constrain dates and rates on different geological timescales. All techniques provide accurate dates with variable precision. Highly precise dates derived by the calculation of the weighted mean and standard error of the mean of zircon dates obtained by in-situ techniques can lead to significantly older suggested emplacement ages than those determined by high-precision CA-ID-TIMS geochronology. This lack in accuracy of the weighted means is due to the protracted nature of zircon crystallisation in upper crustal magma reservoirs, suggesting that standard errors should not be used as a mean to describe the uncertainty in those circumstances. Thus, geologically rapid events or processes or the tempo of magma evolution are too fast to be reliably resolved by in-situ U-Pb geochronology and require ID-TIMS geochronology.

Variations in the Isotopic Composition of Volatilized Lead and the Age of the Western Granodiorite, Yellowknife, Northwest Territories

1975 ◽  
Vol 12 (4) ◽  
pp. 558-573 ◽  
Author(s):  
G. L. Cumming ◽  
F. Tsong
Keyword(s):  
Isotopic Composition ◽  
Time Interval ◽  
Short Time Interval ◽  
Mineral Isochron ◽  
Ore Minerals ◽  
Igneous Activity ◽  
Different Temperatures ◽  
Almost All ◽  
Short Time ◽  
Good Agreement

Large variations in the isotopic composition of Pb volatilized at different temperatures from rocks occur, and are linearly related. The line so obtained may be treated as a mineral isochron and interpreted in the same way as for the equivalent Rb/Sr case. For the western granodiorite at Yellowknife, we obtain a whole rock Pb/Pb age of 2675 m.y. and a series of mineral ages ranging from this upper limit down to about 2500 m.y. The whole rock age is in good agreement with other work and the range of mineral isochron ages is consistent with a cooling interval of about 150 m.y. as deduced by others. A comparison with other recent age determinations from the same area indicates that almost all the significant igneous activity and the emplacement of the ore minerals occurred in a very short time interval around 2650 m.y. ago.

On Multiple Access of a Large Number of Machine-Type Devices in Cellular Networks

2018 ◽  
pp. 105-114
Author(s):  
O. S. Galinina ◽  
S. D. Andreev ◽  
A. M. Tyurlikov
Keyword(s):  
Success Probability ◽  
Random Access ◽  
Time Interval ◽  
Short Time Interval ◽  
Control Mechanisms ◽  
Network Access ◽  
Smart Meters ◽  
Machine To Machine ◽  
Machine To Machine Communication ◽  
Machine Communication

Introduction: Machine-to-machine communication assumes data transmission from various wireless devices and attracts attention of cellular operators. In this regard, it is crucial to recognize and control overload situations when a large number of such devices access the network over a short time interval.Purpose:Analysis of the radio network overload at the initial network entry stage in a machine-to-machine communication system.Results: A system is considered that features multiple smart meters, which may report alarms and autonomously collect energy consumption information. An analytical approach is proposed to study the operation of a large number of devices in such a system as well as model the settings of the random-access protocol in a cellular network and overload control mechanisms with respect to the access success probability, network access latency, and device power consumption. A comparison between the obtained analytical results and simulation data is also offered. 

Concomitant induction to few-layer and 1T-rich two-dimensional MoS2 by rigid segment-containing polysulfide as a sulfur source and in situ intercalator

2021 ◽  
Author(s):  
Yijuan Wang ◽  
Jianzhi Wang ◽  
Jie Liu ◽  
Zhuangwei Xiao ◽  
Yanan Xue ◽  
...  
Keyword(s):  
Sulfur Source ◽  
Two Dimensional ◽  
Rigid Segment

A rigid segment-containing polysulfide was used as a sulfur source and in situ intercalator to induce the formation of few-layer and 1T-rich MoS2.

scholarly journals Improving the Stochastic Model of Ionospheric Delays for BDS Long-Range Real-Time Kinematic Positioning

2021 ◽  
Vol 13 (14) ◽  
pp. 2739
Author(s):  
Huizhong Zhu ◽  
Jun Li ◽  
Longjiang Tang ◽  
Maorong Ge ◽  
Aigong Xu
Keyword(s):  
Real Time ◽  
Long Range ◽  
Ionospheric Delay ◽  
Time Interval ◽  
Short Time Interval ◽  
Dual Frequency ◽  
Triple Frequency ◽  
Ambiguity Fixing ◽  
Power Spectral ◽  
Observation Noise

Although ionosphere-free (IF) combination is usually employed in long-range precise positioning, in order to employ the knowledge of the spatiotemporal ionospheric delays variations and avoid the difficulty in choosing the IF combinations in case of triple-frequency data processing, using uncombined observations with proper ionospheric constraints is more beneficial. Yet, determining the appropriate power spectral density (PSD) of ionospheric delays is one of the most important issues in the uncombined processing, as the empirical methods cannot consider the actual ionosphere activities. The ionospheric delays derived from actual dual-frequency phase observations contain not only the real-time ionospheric delays variations, but also the observation noise which could be much larger than ionospheric delays changes over a very short time interval, so that the statistics of the ionospheric delays cannot be retrieved properly. Fortunately, the ionospheric delays variations and the observation noise behave in different ways, i.e., can be represented by random-walk and white noise process, respectively, so that they can be separated statistically. In this paper, we proposed an approach to determine the PSD of ionospheric delays for each satellite in real-time by denoising the ionospheric delay observations. Based on the relationship between the PSD, observation noise and the ionospheric observations, several aspects impacting the PSD calculation are investigated numerically and the optimal values are suggested. The proposed approach with the suggested optimal parameters is applied to the processing of three long-range baselines of 103 km, 175 km and 200 km with triple-frequency BDS data in both static and kinematic mode. The improvement in the first ambiguity fixing time (FAFT), the positioning accuracy and the estimated ionospheric delays are analysed and compared with that using empirical PSD. The results show that the FAFT can be shortened by at least 8% compared with using a unique empirical PSD for all satellites although it is even fine-tuned according to the actual observations and improved by 34% compared with that using PSD derived from ionospheric delay observations without denoising. Finally, the positioning performance of BDS three-frequency observations shows that the averaged FAFT is 226 s and 270 s, and the positioning accuracies after ambiguity fixing are 1 cm, 1 cm and 3 cm in the East, North and Up directions for static and 3 cm, 3 cm and 6 cm for kinematic mode, respectively.

scholarly journals Evaluation and Validation of a Joint Stress Test to Induce Activity-Related Knee Joint Discomfort — a Prospective Case-Control Study

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Christiane Schön ◽  
Claudia Reule ◽  
Katharina Knaub ◽  
Antje Micka ◽  
Manfred Wilhelm ◽  
...  
Keyword(s):  
Knee Joint ◽  
Healthy Subjects ◽  
Stress Test ◽  
Osteoarthritis Of The Knee ◽  
Time Interval ◽  
Short Time Interval ◽  
Joint Stress ◽  
Joint Health ◽  
The Impact ◽  
Health Function

Abstract Background The assessment of improvement or maintenance of joint health in healthy subjects is a great challenge. The aim of the study was the evaluation of a joint stress test to assess joint discomfort in subjects with activity-related knee joint discomfort (ArJD). Results Forty-five subjects were recruited to perform the single-leg-step-down (SLSD) test (15 subjects per group). Subjects with ArJD of the knee (age 22–62 years) were compared to healthy subjects (age 24–59 years) with no knee joint discomfort during daily life sporting activity and to subjects with mild-to-moderate osteoarthritis of the knee joint (OA, Kellgren score 2–3, age 42–64 years). The subjects performed the SLSD test with two different protocols: (I) standardization for knee joint discomfort; (II) standardization for load on the knee joint. In addition, range of motion (ROM), reach test, acute pain at rest and after a single-leg squat and knee injury, and osteoarthritis outcome score (KOOS) were assessed. In OA and ArJD subjects, knee joint discomfort could be reproducibly induced in a short time interval of less than 10 min (200 steps). In healthy subjects, no pain was recorded. A clear differentiation between study groups was observed with the SLSD test (maximal step number) as well as KOOS questionnaire, ROM, and reach test. In addition, a moderate to good intra-class correlation was shown for the investigated outcomes. Conclusions These results suggest the SLSD test is a reliable tool for the assessment of knee joint health function in ArJD and OA subjects to study the improvements in their activities. Further, this model can be used as a stress model in intervention studies to study the impact of stress on knee joint health function.

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