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21.
卤族元素诸如氯和溴作为地球化学示踪剂,常用于指示岩浆、变质岩和热液的来源和演化过程。而认清溴在造岩矿物中的形态和结构有助于丰富和完善其在地质环境演变中的示踪作用。但是,溴在造岩矿物中的含量极低导致大多数结构分析方法都无法使用,因此造岩矿物中微量溴的结构研究极具挑战性。本文采用 81Br魔角旋转核磁共振(MAS NMR)光谱和同步辐射吸收光谱(XAS)技术,首次对富氯造岩矿物中的微量溴进行了结构分析。结果表明溴离子在方硼石中的微区结构不同于该矿物中三配位Cl原子的结构环境,而与Mg3B7O13Br中八面体配位的溴离子相似,表明即使在微量条件下也存在域偏析。而对其他富氯造岩矿物的Br K边X光吸收近边结构(XANES)光谱白线峰的位置和扩展X射线吸收精细结构(EXAFS)分析表明微量溴离子替代了这些矿物中氯的位置,导致局部结构扭曲膨胀。溴离子在造岩矿物中的这一微观结构研究结果可为探索氯和溴在地质演变过程的指示作用提供新的科学依据。 相似文献
22.
B. A. Ridley T. Zeng Y. Wang E. L. Atlas E. V. Browell P. G. Hess J. J. Orlando K. Chance A. Richter 《Journal of Atmospheric Chemistry》2007,57(3):255-280
During the Tropospheric Ozone Production about the Spring Equinox (TOPSE) program, aircraft flights during April 7–11, 2000
revealed a large area air mass capped below ∼500 m altitude over Hudson Bay, Canada in which ozone was reduced from normal
levels of 30–40 ppbv to as low as 0.5 ppbv. From some of the in-situ aircraft measurements, back-trajectory calculations,
the tropospheric column of BrO derived from GOME satellite measurements, and results from a regional model, we conclude that
the event did not originate from triggering of reactive halogen release in the sub-Arctic region of Hudson Bay but resulted
from such an event occurring at higher latitudes over the islands of the northern Canada Archipelago and nearby Arctic Ocean
with subsequent transport over a distance of 1,000–1,500 km to Hudson Bay. BrO
x
remained active during this transport despite considerable changes in the conditions of the underlying surface suggesting
that chemical recycling during transport dominated any local halogen input from the surface. If all of the tropospheric column
density of BrO is distributed uniformly within the surface layer, then the mixing ratio of BrO derived from the satellite
measurements is at least a factor of 2–3 larger than derived indirectly from in situ aircraft measurements of the NO/NO2 ratio. 相似文献
23.
Timothy Baker Roger Mustard Bin Fu Patrick J. Williams Guoyi Dong Louise Fisher Geordie Mark Chris G. Ryan 《Mineralium Deposita》2008,43(6):599-608
Proterozoic rocks of the Cloncurry district in NW Queensland, Australia, are host to giant (tens to hundreds of square kilometers)
hydrothermal systems that include (1) barren regional sodic–calcic alteration, (2) granite-hosted hydrothermal complexes with
magmatic–hydrothermal transition features, and (3) iron oxide–copper–gold (IOCG) deposits. Fluid inclusion microthermometry
and proton-induced X-ray emission (PIXE) show that IOCG deposits and the granite-hosted hydrothermal complexes contain abundant
high temperature, ultrasaline, complex multisolid (type 1) inclusions that are less common in the regional sodic–calcic alteration.
The latter is characterized by lower salinity three-phase halite-bearing (type 2) and two-phase (type 3) aqueous inclusions.
Copper contents of the type 1 inclusions (>300 ppm) is higher than in type 2 and 3 inclusions (<300 ppm), and the highest
copper concentrations (>1,000 ppm) are found both in the granite-hosted systems and in inclusions with Br/Cl ratios that are
consistent with a magmatic source. The Br/Cl ratios of the inclusions with lower Cu contents are consistent with an evaporite-related
origin. Wide ranges in salinity and homogenization temperatures for fluid inclusions in IOCG deposits and evidence for multiple
fluid sources, as suggested by halogen ratios, indicate fluid mixing as an important process in IOCG genesis. The data support
both leaching of Cu by voluminous nonmagmatic fluids from crustal rocks, as well as the direct exsolution of Cu-rich fluids
from magmas. However, larger IOCG deposits may form from magmatic-derived fluids based on their higher Cu content. 相似文献