Porphyry-type Mo deposits have supplied most of the Mo to the world. However, the source of the Mo and the controls on its enrichment in such deposits is still a matter of great debate. In this ...study, we present in situ trace element and isotopic data for a giant porphyry Mo deposit (the Chalukou Mo deposit in NE China) and use these data to address these issues. Three primary paragenetic stages of mineralization were recognized at Chalukou: (Stage I) K-feldspar + quartz + minor pyrite (Py-I) + minor molybdenite (Mol-I); (Stage II) quartz + sericite + molybdenite (Mol-II) + pyrite (Py-II); (Stage III) quartz + chlorite + epidote + fluorite + pyrite (Py-III) + galena + sphalerite + minor chalcopyrite. The bulk of the molybdenite was deposited in Stage II. In situ S isotope analyses of the sulfide ores show that the δ34S values vary from -5.2 to +7.8 ppm (mean = +2.9 ppm) and correspond to δ34SH2S values from -2.4 to +3.3 ppm (mean = +1.1 ppm). These values are consistent with a magmatic source for the sulfur. In situ Pb isotope compositions of the sulfide ores are almost identical to those of the local Mesozoic granites and other magmatic-hydrothermal ore deposits in this region, suggesting a close genetic association between the Mo mineralization and felsic magmatism. Pyrite from the three stages of mineralization differs significantly in its trace element composition. The first generation, Py-I, has a high Cu content (8.7 ± 49.6 ppm; where the first value is the median and the second is the standard deviation) and Mo content (6.9 ± 3.8 ppm). Pyrite-II has the lowest Cu concentration (1.3 ± 2.1 ppm) and a relatively high Mo concentration (5 ± 128 ppm), and Py-III has a high Cu content (8.7 ± 37.1 ppm) but the lowest Mo content (0.05 ± 5.7 ppm). From this, we infer that pyrite recorded the chemical evolution in the Mo/Cu ratio of the ore fluid and that this ratio reached a maximum in Stage II, coinciding with the widespread saturation of the fluid in molybdenite. The evolution of the Mo/Cu ratio in pyrite implies that the fluid was undersaturated in chalcopyrite at the high temperature of Stage I, despite the Cu concentration of the fluid apparently being at its high level, and chalcopyrite only saturated later, at a lower temperature. Molybdenite, however, because of its lower solubility, saturated early (Stage I) and in the subsequent stage (Stage II) was supersaturated in the fluid. There is a significant enrichment of Mo in the syn-ore intrusions at Chalukou compared to the pre-ore monzogranite. The very low Sr/Y ratios for the Chalukou syn-ore intrusions, which are in sharp contrast to the high Sr/Y ratios of the pre-ore monzogranite and those of porphyries related to Cu deposits, suggest that fractional crystallization of plagioclase may have been a key factor in generating the syn-ore magmas. Molybdenum is a highly incompatible metal and will concentrate in the crust, and assimilation of old continental crust, therefore, may explain the Mo enrichment of the syn-ore intrusions and ultimately the formation of the giant Chalukou deposit.
Numerous skarn-type Sn deposits have been identified in the Nanling Range (South China), of which the Shizhuyuan W-Sn-Bi-Mo, Xianghualing Sn, Jinchuantang Sn-Bi, and Hehuaping Sn deposits are the ...largest. The Xianghualing deposit, which is the focus of this study, hosts a resource of 0.17 Mt Sn grading 0.93-1.39 wt% SnO2. Whether the distal skarn-type mineralization and the cassiteritesulfide vein-type orebody in the Xianghualing district are genetically related to the Laiziling granitic pluton, which produced the proximal skarn-type Sn mineralization, however, is still unknown. The Xianghualing Sn mineralization occurs exclusively as cassiterite and has been subdivided into four ore-types: (1) lenticular proximal skarn ore (Cst I) containing the mineral assemblage cassiteritepyrrhotite-chalcopyrite-actinolite-wollastonite; (2) layered distal skarn ore (Cst II) containing the mineral assemblage cassiterite-pyrrhotite-chalcopyrite-actinolite; (3) vein cassiterite-sulfide ore (Cst III) distal from the skarn and associated granite containing the mineral assemblage cassiterite-arsenopyrite-pyrrhotite-muscovite-fluorite; and (4) veinlet Sn-Pb-Zn ore (Cst IV) distal from the skarn and associated granite containing the mineral assemblage cassiterite-galena-sphalerite-topaz-quartz. Here, we report the results of in situ laser ablation inductively coupled plasma mass spectrometric (LA-ICPMS) U-Pb age determinations for garnet from the Xianghualing skarn and the above four types of cassiterite. Our age determinations indicate that there were two independent magmatic-hydrothermal events at ∼160 and 156∼150 Ma, both of which led to Sn mineralization. The first Sn mineralization event at DF160 Ma (Cst IV U-Pb ages of 159.6 ± 1.4 to 158.5 ± 0.8 Ma) is interpreted to have been associated with a speculative unexposed granitic pluton, which is coeval with the nearby Jianfengling granite intrusion. The second Sn mineralization event at 156∼150 Ma (Cst I to Cst III U-Pb ages of 155.9 ± 0.7 to 152.3 ± 1.1 Ma and garnet U-Pb ages of 153.6 ± 7.6 to 151.5 ± 3.5 Ma) is genetically related to the adjacent Laiziling granitic intrusion (152.8 ± 1.2 Ma, zircon U-Pb age). This event was responsible for the bulk of the Sn resource (>95%). Our age determinations provide convincing evidence for superimposed Jurassic Sn mineralizing systems at Xianghualing. They also show the value of combining garnet and cassiterite U-Pb age determinations to constrain the timing of skarn and Sn mineralization and distinguish discrete Sn mineralizing events in a protracted metallogenic history.
Skarn-type tungsten deposits are widely distributed all over the world and contribute more than 70% of the world's W supply. The temporal relation between the W mineralization and causative ...intrusions and the evolution of ore-forming fluids are matters of ongoing debate. In this study, we combine in situ LA-ICP-MS U-Pb dating and trace element compositions of scheelite from Zhuxi, the world's largest W deposit, and compare them with literature data to address the above issues. Three primary ore stages exist at Zhuxi: prograde skarn, retrograde skarn, and quartz-sulfide stages. Most scheelite occurs in the retrograde skarn stage and is further subdivided into three generations: Sch A, B, and C. The obtained LA-ICP-MS U-Pb ages for three scheelite generations in the Zhuxi deposit are 154.0 ± 2.8, 150.3 ± 3.5, and 150.4 ± 6.3 Ma, respectively, indicating that the entire W mineralization is closely related to the emplacement of the nearby Late Jurassic granites (∼154 to 150 Ma, zircon U-Pb ages). In situ LA-ICP-MS trace element results demonstrate that Sch A shows the highest Mo content (mean = 1002 ppm), where those for Sch B and Sch C are 109 and 45 ppm, respectively. These, combined with the gradually increasing trend of Ce contents and δCe values, indicate a shift from oxidizing to reducing conditions for the ore-forming fluid. All three scheelite generations yield significant positive δEu anomalies, which are considered to be unrelated to the redox state, but caused by the addition of Eu (e.g., feldspar dissolution). The high-Y/Ho ratio of scheelite and a good correlation between Y/Ho ratio and δEu (R2 = 0.96) suggest that intense fluid-rock interactions between ore fluids and the Shuangqiaoshan Group metasedimentary rocks as well as earlier-formed skarns drove fluid evolution. This study demonstrates that scheelite U-Pb geochronology is a useful technique when identifying the temporal link between hydrothermal W mineralization and the causative intrusion. Our results also highlight that the reactions of the ore fluids with wall rocks and earlier-formed skarns significantly modify the primary fluid compositions.
Understanding human mobility is crucial for a broad range of applications from disease prediction to communication networks. Most efforts on studying human mobility have so far used private and low ...resolution data, such as call data records. Here, we propose Twitter as a proxy for human mobility, as it relies on publicly available data and provides high resolution positioning when users opt to geotag their tweets with their current location. We analyse a Twitter dataset with more than six million geotagged tweets posted in Australia, and we demonstrate that Twitter can be a reliable source for studying human mobility patterns. Our analysis shows that geotagged tweets can capture rich features of human mobility, such as the diversity of movement orbits among individuals and of movements within and between cities. We also find that short- and long-distance movers both spend most of their time in large metropolitan areas, in contrast with intermediate-distance movers' movements, reflecting the impact of different modes of travel. Our study provides solid evidence that Twitter can indeed be a useful proxy for tracking and predicting human movement.
V600E and
promoter mutations, particularly their genetic duet, are well known to be associated with poor clinical outcomes of papillary thyroid cancer (PTC). Loss of radioactive iodine (RAI) avidity ...in recurrent PTC is a major cause of treatment failure and hence poor clinical outcomes. This study investigated the role of mutation patterns in loss of RAI avidity in recurrent PTC.
This was a retrospective study of the relationship between loss of RAI avidity in structural recurrent PTC and the genotype patterns of
V600E and
promoter mutations in 164 patients (104 women and 60 men) with a median age of 50 y (interquartile range, 35-62 y).
The overall prevalence of RAI avidity loss in recurrent PTC was 62.8% (103/164). When the cohort was divided into mutation and wild-type groups, the RAI avidity loss was 80.4% versus 33.9% (
< 0.001) in
V600E versus wild-type
patients, with an adjusted odds ratio of 7.11 (95% confidence interval CI, 3.24-16.27), and 89.4% versus 52.1% (
< 0.001) in
mutation versus wild-type patients, with an adjusted odds ratio of 6.89 (95% CI, 2.28-25.66). When the cohort was divided into 4 genotypes, the RAI avidity loss was 70.3% (45/64), 55.6% (5/9), and 97.4% (37/38) in patients with
V600E alone,
mutation alone, and the genetic duet of coexisting
and
mutations, versus 30.2% (16/53) in patients with neither mutation (
< 0.001, = 0.251, and < 0.001, respectively). These corresponded to odds ratios of 5.39 (95% CI, 2.31-13.13), 2.84 (95% CI, 0.53-16.32), and 81.04 (95% CI, 11.67-3559.83), respectively. The synergy index was 13.28 (95% CI, 1.54-114.46;
= 0.019) between
V600E and
mutation in cooperatively affecting RAI avidity. A similar genotype-associated expression pattern was observed for thyroid iodide-handling genes.
V600E alone and, particularly, coexisting
V600E and
promoter mutations are strongly associated with loss of RAI avidity and impairment of the iodide-metabolizing machinery in recurrent PTC, showing a robust predictive value for failure of RAI treatment of PTC.
•Effect of LSP on tensile behavior of the SLMed Ti6Al4V alloy was studied.•LSP generated compressive residual stress in surface layer of SLMed sample.•Dislocations and nano twins were induced in ...SLMed sample by LSP.•LSP realized excellent combination of strength and ductility in SLMed sample.•The mechanism of the tensile property enhancement by LSP was revealed.
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In this work, the influences of laser shock peening (LSP) on the residual stress state, microstructures and mechanical properties of Ti-6Al-4V alloy fabricated by selective laser melting (SLM) were researched. Particularly, the microstructural evolution before and after LSP was clarified using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) observations. The results showed that the residual stress was adjusted from tensile to compressive state. Furthermore, high-density dislocations and a great number of parallel nano mechanical twins (nano-MTs) were promoted in the coarse lamellar α' structures, contributing to the grain refinement. The ultimate tensile strength and elongation of the SLM-manufactured (SLMed) Ti-6Al-4V alloy increased by approximately 14.3% and 18.3% after LSP treatment, respectively. Finally, the dominant mechanism of tensile property enhancement by LSP was revealed. High levels of compressive residual stress and grain refinement of the α' structures induced by LSP realized the excellent combination of strength and ductility.
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•The LA-ICP-MS analysis of pyrite indicates the gold occurring as Au1+, and the silver in Ag-bearing sulfosalt inclusion.•Pyrite trace element compositions can reflect physicochemical ...conditions of the hydrothermal fluids.•Combined geological and mineralogical evidences could confirm the genetic type of gold deposit.
The Dafang is a hydrothermal gold deposit (6 t Au with an average grade of 1.8 g/t) in periphery of the Sn-Cu metallogenic system in Nanling Range in south China. This deposit locates in the contact zone between late Jurassic granodiorite porphyry and late Paleozoic limestone as well as the fractures of them. The mineralization comprises three stages, pyrite + arsenopyrite ± chalcopyrite + quartz (I), pyrite + arsenopyrite + gold + calaverite + sulfosalt ± sphalerite ± galena + quartz (II), and pyrite + arsenopyrite + quartz + calcite (III). Pyrite is the dominant gold-bearing mineral, which can be classified into three generations (Py1 to Py3), corresponding to three ore stages (Stage I to Stage III), respectively. Different stage pyrites show textural homogeneity in both reflected light and backscattered electron images. In addition, the LA-ICP-MS results show that all pyrites have relatively low Au concentrations (0.17 ppm for Py1, 0.48 ppm for Py2 and 0.58 ppm for Py3), and trace element mapping for Py1 demonstrate oscillatory zoning patterns for Au, As, Sb, Te, Co, and Ni. Compared to Py2 and Py3, Py1 has higher Co, Ni, Cu, Pb, Zn, Ag, and Te contents, but lower Au and Tl contents. Gold contents for all stage pyrite plot well below the solubility limit for gold in arsenian pyrite, indicating that invisible gold occurs as Au1+ in the pyrite lattice. Silver occurs mainly as Ag-bearing sulfosalt inclusion or galena micro-inclusion in pyrite, while Pb and Zn as galena and sphalerite micro-inclusions in pyrite. Trace element mapping yields that Au-rich zone coincides well with As rich zones, demonstrating that the occurrence of As in pyrite promotes the enrichment of lattice gold. From Stage I to Stage III, the decrease of Co and Ni contents indicates the decrease of the ore-fluid temperature, and the change of Se and Te contents suggests the fO2 increased from Stage I to Stage II and then decreased to Stage III. The Co and Ni contents suggest that all studied pyrite is dominantly of hydrothermal origin. Combined geological and mineralogical evidences indicate that the Dafang gold deposit is an epithermal Au deposit.
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