ALBERT

Description: The Middle-Lower Yangtze River Valley Belt (MLYRB) in South China contains many stratabound Fe-Cu-Pb-Zn deposits hosted in Middle-Upper Carboniferous carbonates. The origin and nature of the ore fluids are poorly constrained (syngenetic vs. epigenetic). Trace elements and sulfur isotope compositions of sphalerite and galena from the Qixiashan carbonate-hosted Pb-Zn deposit (Eastern of MLYRB) help to clarify the ore-fluid source and metallogenic processes. Three types of sphalerites have been distinguished (black sphalerite a, zoned sphalerite b and light color sphalerite c). High Fe and Mn contents of the early black sphalerite (Sp-a) were possibly derived from preceding Fe-Mn-rich sulfide layer or sediments from ore-bearing strata via replacement at 274–315 °C. The zoned sphalerite (Sp-b) has a dark Fe-Cu-rich core (321–348 °C) overgrown by a light Fe-Cu-poor rim (285–314 °C). The Sp-b rims are compositionally similar to Sp-a, Therefore, zoned Sp-b possibly represents the transition stage from poor copper (Sp-a) to rich copper (Sp-c) fluids. The light-color late sphalerite (Sp-c) is characterized by Fe-Mn depletion, as well as Ga, Cu, Cd and Sn enrichments. The Ga-rich Sp-c was possibly precipitated by the mixing of Ga-bearing sulfate and metalliferous fluid at 146–255 °C. We considered the Qixiashan Pb-Zn deposit to be of epigenetic origin that has undergone multistage ore-forming processes, in which the ore sulfur (δ34S: –3.7‰ to +7.8‰) was sourced from seawater sulfate (+22‰) via thermochemical sulfate reduction (TSR).

Description: Presented are analytical data from lacustrine sediment cores, retrieved from Lake Nam Co (Tibetan Plateau). The sediment core is a composite of one gravity core, taken with a Rumohr-Meischner gravity corer (63 mm diameter) and a piston core, retrieved using an uwitec piston coring system (http://www.uwitec.at; 90 mm diameter). The composite core labelled 〈NC 08/01〉 comprises a total length of 10.378 m. The cores were obtained at N 30.737417, E 090.790333 at a water depth of 93 m on 2008-09-15. The purpose of obtaining this sediment core was to establish a high-resolution record of climate (monsoonal) and environmental change using multiple proxy data. The dataset comprises analytical data based on sedimentological, inorganic geochemical, mineralogical and isotope-geochemical methods. Specifically: sediment water content & density; magnetic susceptibility; particel size data; quantitative inorganic geochemical data (ICP-OES aqua regia and HCL digestions); semi-quantitative XRF elemental data; carbon, nitrogen, sulfur contents; qualitative mineralogical data; bulk sediment stable carbon and oxygen isotope data.

Description: The mechanisms controlling the enrichment and separate precipitation of tungsten and tin ores are obscure. To unravel the physicochemical changes in the mineralization system during the magmatic-hydrothermal transition, we investigate the petrography, geochemistry, and boron isotopes of tourmaline in the Wangxianling-Hehuaping district (Nanling Range, South China). Four types of tourmalines were identified: Magmatic (Tur-WG) and hydrothermal (Tur-WV) tourmaline in the Triassic W-mineralized tourmaline-two-mica granite (ca. 220 Ma); Magmatic (Tur-SnG) and hydrothermal (Tur-SnV) tourmaline in the Jurassic Sn-mineralized biotite granite (ca. 155 Ma). Tur-WV and Tur-SnV have lower Fe3+/(Fe2+ + Fe3+) ratios than those of Tur-WG and Tur-SnG, suggesting that W-Sn mineralization occurred in a relatively reducing environment. In addition, the δ11B values of all four types of tourmalines are similar, suggesting that the ore-forming fluids were primarily exsolved from the granitic magma. Significant chemical variations (e.g., Mg, Fe, Sc, V, Ni, and REEs) between Tur-SnG and Tur-SnV may have been resulted from fractionation and intense ore fluid-wall rock reactions. In contrast, Tur-WG has similar chemical compositions to Tur-WV, suggesting that the Triassic W mineralization may have undergone a magmatic-hydrothermal process with little ore fluid-wall reaction. Tur-SnV has exceptionally high F content, which could enhance the Sn solubility and enrichment. This explains the low Sn content of granitic magmas with large-scale Jurassic tin mineralization. Considering that W has a large melt-fluid partition coefficient, we conclude that in the Triassic, W is enriched in the exsolved fluid from the granitic magma and precipitated with temperature drop. This may have caused the decrease in W content in the protolith and limited the Jurassic W mineralization. Subsequently, the mantle-derived F addition along the Chenzhou-Linwu fault in the Jurassic had led to Sn enrichment in the fluids, and mineralization is triggered by temperature drop and fluid-rock reactions. Eventually, the extensive Triassic W mineralization and Jurassic Sn mineralization exhibit the separation of tungsten-tin mineralization. The separated tungsten-tin mineralization model based on different volatile components could also be applicable to other tungsten-tin metallogenic belts.

Description: In the most commonly used mass flux scheme of many cumulus parameterization schemes, entrainment and detrainment rates are important quantities. To improve parameterization of the two quantities, it is critical to accurately obtaining them in observations and understanding the factors affecting them. A new approach is developed for simultaneously estimating entrainment and detrainment rates in cumulus clouds by deriving equations relating entrainment and detrainment rates to gross entrainment and detrainment. The approach has been applied to shallow cumulus aircraft observations around the world, including the Holistic Interactions of Shallow Clouds, Aerosols, and Land-Ecosystems (HI-SCALE), the Routine AAF Clouds with Low Optical Water Depths (CLOWD) Optical Radiative Observations (RACORO), the Rain in Cumulus over the Ocean (RICO), the Small Cumulus Microphysics Study (SCMS), the Cumulus Photogrammetric, In-Situ and Doppler Observations (CuPIDO), the Green Ocean Amazon (GoAmazon), the Cloud System Evolution in the Trades (CSET), the Cloud Land Surface Interaction Campaign (CLASIC), the Joint Hawaii Warm Rain Project (JHWRP), and the Elucidating the Role of Clouds-Circulation Coupling In Climate (EUREC4A) field campaigns. Results show that both entrainment and detrainment rates decrease with increasing height, and sensitivity tests with different entrained and detrained air assumptions yield similar results. Buoyancy and vertical velocity have significant impacts on entrainment rate. These results from global aircraft observations will be used to establish parameterizations of entrainment and detrainment rates.