Search

The formation of tectonic magmatic-related emerald deposits necessarily invokes a mixing model of Be-rich granitic rocks and Cr and/or V-rich surrounding rocks. However, there has been continuing debate on the deposit genesis, with the essential controversy being the relative significance of magma versus metamorphism in mineralizing as well as the key triggers for emerald deposition. The Dayakou emerald deposit genetically related to the Cretaceous granitic magmatism and hosted within the Neoproterozoic metasedimentary rocks is an ideal study case to probe into the above outstanding issue. In this paper, three hydrothermal mineralization and related alteration stages have been recognized in Dayakou, comprised of the greisenization and early emerald mineralization in high-temperature hydrothermal condition (stage-I; peak at 380 °C to 480 °C), the silicification and main emerald mineralization in medium–high temperature fluid (stage-II; peak at 300 °C to 360 °C) and the late carbonate alteration and scheelite mineralization (stage-III). Analysis results of fluid inclusion and C–H–O isotopes of emeralds and associated minerals suggest that ore-forming fluids belong to the H2O–NaCl ± CO2 system with minor H2S, CH4, and N2, exsolved from the Cretaceous granites and gradually interacted with the surrounding metamorphic rocks. We combine the new data with those reported in earlier studies to further propose a genesis scenario for the Dayakou deposit, in which Be-bearing fluids originally exsolved from peraluminous melts and fluoride complexes may be an effective transport proxy for Be in hydrothermal fluids. Fluid boiling during fluid ascent leads to the significant fractionation and enrichment of elements and the escape of volatiles (e.g., HF, H2O, CO2) in ore system. Meanwhile, sustained fluid-rock interaction (e.g., greisenization) increasingly extracts Cr, V and Ca into fluids to facilitate mineral precipitation, wherein the crystallization of fluoride minerals would cause the destabilization of Be-F complexes. Our study indicates that fluid boiling and fluid-rock interactions are the primary triggers for emerald deposition.

Compressional stress in collisional orogenic belts open a free boundary for the lateral extrusion of rigid blocks. Here we trace the history of tectonic escape of a Proterozoic microplate and the associated inhomogeneous crust-mantle processes from magmatic records in the Bikou Terrane, which is the largest microblock located among the North China Block, South China Block and Songpan-Ganzi Orogenic Belt. Zircon U-Pb geochronology indicates that the Triassic granitoid intrusions in the Bikou Terrane emplaced at 220–210 Ma. Petrographical, whole-rock geochemical and isotopical features suggest that the granitoids derived from the partial melting of lower crust, with inhomogeneous contribution of mafic magma derived from partial melting of subcontinental lithospheric mantle. Compared with the Yangba pluton in northeastern Bikou Terrane, the five intrusions in the southwestern Bikou Terrane display relatively lower REE concentrations, more negative Eu anomalies (δEu = 0.24–0.93), and lower Nb/Ta and Zr/Hf ratios with the values of 14–20 and 37–45. Furthermore, they display higher (87Sr/86Sr) i from 0.7050 to 0.7075 and lower eNd(t) from −9.4 to −4.7. These features imply that the granitic intrusions in southwestern Bikou Terrane were primary derived from the partial melting of the lower crust with lesser input of mantle materials than the Yangba pluton, indicating inhomogeneous crust-mantle interaction in the Bikou Terrane. We calculated the Moho depth of northeast and southwest Bikou Terrane as ~60 km and ~ 40–50 km, respectively. We propose that the Bikou Terrane escaped southwestward in Late Triassic following a transition in the stress regime of compression from NE-SW to NW-SE, in addition to the slab break-off from east to west. The lateral extrusion resulted in the inhomogenous crust-mantle interaction.

The Cretaceous Dayakou emerald deposit (southwest China) hosted in the Neoproterozoic schists and granofels is a magmatic-hydrothermal ore system. In this paper, we present the petrological and geochemical study of tourmaline from the Dayakou deposit, aiming to constrain the source of ore-forming fluid and emerald genesis. Two types of tourmaline, namely type-I formed in emerald-bearing quartz veins and type-II in non-mineralized quartz veins, are distinguished and analyzed in situ for their chemical and boron isotopic compositions. All tourmalines are close to the dravite endmember and belong to the alkali group. The type-I tourmaline has a higher Fe/(Fe + Mg) ratio (0.28–0.47) with Li enrichment (21–227 ppm). The type-II tourmaline, however, shows a lower Fe/(Fe + Mg) ratio (0.14–0.34) with relatively higher Co (2–3 ppm) and REEs (2–21 ppm) content. Boron isotopic composition in tourmaline (δ11B = −15.8‰ to −10.4‰) is closed to the average boron composition of continental crust. The boron isotope variations could be the result of rapid precipitation of tourmaline from a magmatic-hydrothermal fluid or the mixing with a metamorphic fluid. Based on the chemical composition and enrichment in granitophile elements (e.g., Li, Be, Sn) and transition metals (e.g., Ti, V, Cr) in tourmaline, we propose that the Dayakou deposit is dominantly controlled by the fluid-rock interaction between the metamorphic basement and possibly reduced magmatic-hydrothermal fluids. Beryllium is transported as fluoride complex in fluids. Hydrothermal fluids continuously interacted with surrounding rocks to extract Cr, V, and Ca into fluids, resulting in extensive crystallization of fluorine minerals (e.g., fluorite, fluorapatite, etc.) and subsequent destabilization of Be-F complexes. The large amounts of Be, Cr and V enriched in the fluid then combine to form emeralds. The Li, Co, and REEs contents of tourmaline can be used as the exploration indicator to target emerald mineralization in this region.

Several 2-anilino- and 2-benzylamino-3-deaza-6-oxopurines [3-deazaguanines] and selected 8-methyl and 8-aza analogs have been synthesized. 7-Substituted N2-(3-ethyl-4-methylphenyl)-3-deazaguanines were potent and selective inhibitors of Gram+ bacterial DNA polymerase (pol) IIIC, and 7-substituted N2-(3,4-dichlorobenzyl)-3-deazaguanines were potent inhibitors of both pol IIIC and pol IIIE from Gram+ bacteria, but weakly inhibited pol IIIE from Gram− bacteria. Potent enzyme inhibitors in both classes inhibited the growth of Gram+ bacteria (MICs 2.5–10 μg/ml), and were inactive against the Gram− organism Escherichia coli. Several derivatives had moderate protective activity in Staphylococcus aureus-infected mice.

Numerous 3-substituted-6-(3-ethyl-4-methylanilino)uracils (EMAU) have been synthesized and screened for their capacity to inhibit the replication-specific bacterial DNA polymerase IIIC (pol IIIC) and the growth of Gram+ bacteria in culture. Direct alkylation of 2-methoxy-6-amino-4-pyrimidone produced the N3-substituted derivatives, which were separated from the byproduct 4-alkoxy analogues. The N3-substituted derivatives were heated with a mixture of 3-ethyl-4-methylaniline and its hydrochloride to effect displacement of the 6-amino group and simultaneous demethylation of the 2-methoxy group to yield target compounds in good yields. Certain intermediates, e.g. the 3-(iodoalkyl) compounds, were converted to a variety of (3-substituted-alkyl)-EMAUs by displacement. Most compounds were potent competitive inhibitors of pol IIIC (K(i)s 0.02-0.5 microM), and those with neutral, moderately polar 3-substituents had potent antibacterial activity against Gram+ organisms in culture (MICs 0.125-10 microg/mL). Several compounds protected mice from lethal intraperitoneal (ip) infections with S. aureus (Smith) when given by the ip route. A water soluble derivative, 3-(4-morpholinylbutyl)-EMAU hydrochloride, given subcutaneously, prolonged the life of infected mice in a dose dependent manner.

7-Substituted-N(2)-(3,4-dichlorobenzyl)guanines potently and competitively inhibit DNA polymerases IIIC and IIIE from Gram(+) bacteria. Certain derivatives are also competitive inhibitors of DNA polymerase IIIE from Gram(-) bacteria.

Certain substituted 6-anilinouracils are potent and selective inhibitors of Gram+ bacterial DNA polymerase IIIC (pol IIIC). In addition, analogues with 3-substituents in the uracil ring have potent antibacterial activity against Gram+ organisms in culture. In an attempt to find optimal anilino substituents for pol IIIC binding and optimal 3-substituents for antibacterial activity, we have prepared several series of 3-substituted-6-aminouracils and assayed their activity against pol IIIC from Bacillus subtilis and a panel of Gram+ and Gram- bacteria in culture. The 6-(3-ethyl-4-methylanilino) group and closely related substituent patterns maximized pol IIIC inhibition potency. Among a series of 3-(substituted-butyl)-6-(3-ethyl-4-methylanilino)uracils, basic amino substituents increased pol IIIC inhibition, but decreased antibacterial activity. The most potent antibacterials were simple hydroxybutyl and methoxybutyl derivatives, and hydrophobically substituted piperidinylbutyl derivatives.

Treatment of electron-rich aromatic and heteroaromatic compounds with per(poly)fluoroalkyl chlorides in the presence of sodium dithionite in DMSO gives the corresponding fluoroalkylated products in moderate to good yields. The structures and yields of products depend mainly on the position and electron-donating ability of the substituents on the aromatic compounds.

2,2,2-Trifluoroethylation of alkenes and alkynes with 2,2,2-trifluoroethyl iodide or bromide and sodium dithionite in D+MSO or CH 3 CN H 2 O can occur under mild conditions.

2,2,2-Trifluoroethyl chloride, bromide, iodide but not fluoride react with thiolate ions in DMF under laboratory illumination at 30–50 °C to give the 2,2,2-trifluoroethylthiol derivatives in high yields. The acceleration by UV irradiation, suppression by p -dinitrobenzene or hydroquinone and detection of trifiuoroethyl radical by ESR spectroscopy show that the reactions occur by S RN 1 mechanism. The initiation step may be spontaneous or thermal electron transfer between thiolate and halides because the reactions can occur in dark.

The trifluoromethylation of organic halides with FO2SCF2CF2OCF2CO2K (1) in DMF can be accomplished at 45 °C which is advantageous for thermally sensitive substrates. α-Carbon-oxygen bond fragmentation of 1 and the related β-carbon-oxygen bond scission are discussed.

The trifluoromethylation of organic halides with FO2SCF2CF2OCF2CO2K (1) in DMF can be accomplished at 45 °C which is advantageous for thermally sensitive substrates. α-Carbon-oxygen bond fragmentation of 1 and the related β-carbon-oxygen bond scission are discussed.

2,2,2-Trifluoroethyl chloride, bromide, iodide but not fluoride react with thiolate ions in DMF under laboratory illumination at 30–50 °C to give the 2,2,2-trifluoroethylthiol derivatives in high yields. The acceleration by UV irradiation, suppression by p -dinitrobenzene or hydroquinone and detection of trifiuoroethyl radical by ESR spectroscopy show that the reactions occur by S RN 1 mechanism. The initiation step may be spontaneous or thermal electron transfer between thiolate and halides because the reactions can occur in dark.

2,2,2-Trifluoroethylation of alkenes and alkynes with 2,2,2-trifluoroethyl iodide or bromide and sodium dithionite in D+MSO or CH 3 CN H 2 O can occur under mild conditions.

In DMSO, the addition reactions of perfluoroalkyl chlorides, RFCl, to alkenes or alkynes can occur smoothly in the presence of 1.5 equiv of Na2S2O4 and NaHCO3 at 75−80 °C for 4−10 h to give the corresponding adducts (RCH2CH2RF or RCHCHRF). Ethyl chlorofluoro- (1f), chlorodifluoro- (1g) acetates, even nonfluorinated compounds, such as ethyl dichloro- (1h), chloro- (1i) acetates, and chloroform (1j) can undergo the similar reaction. Treatment of ω-iodo (or chloro-) perfluoroalkyl chlorides [X(CF2)nCl, n = 2, 4, X= I or Cl] with >3 equiv of alkenes and Na2S2O4 gives directly the symmetrically disubstituted alkanes (RCH2CH2)2(CF2)n. The symmetrically and unsymmetrically disubstituted adducts RCH2CH2(CF2)nCH2CH2R‘ from ω- iodoperfluoroalkyl chlorides can be also obtained stepwise, i.e., through the further addition reactions of monoadducts, RCH2CH2(CF2)nCl to olefins. However, for α,ω-dichloroperfluoroalkanes, the similarly stepwise reactions with an alkene is not clean, both bis-adducts and the corresponding ...

Treatment of electron-rich aromatic and heteroaromatic compounds with per(poly)fluoroalkyl chlorides in the presence of sodium dithionite in DMSO gives the corresponding fluoroalkylated products in moderate to good yields. The structures and yields of products depend mainly on the position and electron-donating ability of the substituents on the aromatic compounds.

Novel Gram-positive (Gram+) antibacterial compounds consisting of a DNA polymerase IIIC (pol IIIC) inhibitor covalently connected to a topoisomerase/gyrase inhibitor are described. Specifically, 3-substituted 6-(3-ethyl-4-methylanilino)uracils (EMAUs) in which the 3-substituent is a fluoroquinolone moiety (FQ) connected by various linkers were synthesized. The resulting "AU-FQ" hybrid compounds were significantly more potent than the parent EMAU compounds as inhibitors of pol IIIC and were up to 64-fold more potent as antibacterials in vitro against Gram+ bacteria. The hybrids inhibited the FQ targets, topoisomerase IV and gyrase, with potencies similar to norfloxacin but 10-fold lower than newer agents, for example, ciprofloxacin and sparfloxacin. Representative hybrids protected mice from lethal Staphylococcus aureus infection after intravenous dosing, and one compound showed protective effect against several antibiotic-sensitive and -resistant Gram+ infections in mice. The AU-FQ hybrids are a promising new family of antibacterials for treatment of antibiotic-resistant Gram+ infections.

In DMSO, the addition reactions of perfluoroalkyl chlorides, R(F)Cl, to alkenes or alkynes can occur smoothly in the presence of 1.5 equiv of Na(2)S(2)O(4) and NaHCO(3) at 75-80 degrees C for 4-10 h to give the corresponding adducts (RCH(2)CH(2)R(F) or RCH=CHR(F)). Ethyl chlorofluoro- (1f), chlorodifluoro- (1g) acetates, even nonfluorinated compounds, such as ethyl dichloro- (1h), chloro- (1i) acetates, and chloroform (1j) can undergo the similar reaction. Treatment of omega-iodo (or chloro-) perfluoroalkyl chlorides [X(CF(2))(n)()Cl, n = 2, 4, X= I or Cl] with3 equiv of alkenes and Na(2)S(2)O(4) gives directly the symmetrically disubstituted alkanes (RCH(2)CH(2))(2)(CF(2))(n)(). The symmetrically and unsymmetrically disubstituted adducts RCH(2)CH(2)(CF(2))(n)()CH(2)CH(2)R' from omega- iodoperfluoroalkyl chlorides can be also obtained stepwise, i.e., through the further addition reactions of monoadducts, RCH(2)CH(2)(CF(2))(n)()Cl to olefins. However, for alpha,omega-dichloroperfluoroalkanes, the similarly stepwise reactions with an alkene is not clean, both bis-adducts and the corresponding omega-hydrides, RCH(2)CH(2)(CF(2))(n)()H as byproducts are also formed. In the absence of alkenes or alkynes, per- and polyfluoroalkyl chlorides can be converted to their sulfinate salts and sulfonyl chlorides.

Room-temperature ferromagnetism (FM) is observed in Si-Al2O3 amorphous composite film. The magnetic moment is the highest in the case of the Si-Al2O3 composite films with the Si content being 15 vol.%, and distinct domains are detected in our films. The difference in magnetism property between sample annealed in Ar atmosphere and untreated composite film indicates that the observed ferromagnetism does not originate primarily from oxygen defects. It is concluded that the ferromagnetism arises from the direct coupling between defects. These defects orignate from the interface between Si particles and Al2O3 matrix. By varying the Si content in the film, one can change the defect density and thereby control the strength of the ferromagnetic coupling.