Deforestation,biomass and carbon finance in Amazonia     

《Climate Policy》2013,13(1):7-22

Biomass dynamics in Amazonia are quantified and the value that carbon finance could deliver from slowing deforestation is assessed. Above-ground forest biomass in the Legal Amazon shrank from 90 Pg to 76 Pg between 1978 and 2004. An average decrease of 0.64 Pg (standard error 0.38 Pg) per year was estimated for primary and econdary vegetation. For an improved, spatially and temporally explicit estimation, a time series of remote-sensing results and a model of secondary forest area and age distribution was combined with a large-scale forest-growth model. The observed trend of biomass decline is continuous and defines a baseline that the avoidance of deforestation could be measured against. Based on scenario calculations, the emission reductions from slightly reduced deforestation rates could be valued in the range of €1 billion annually. Carbon finance for reducing emissions from deforestation (‘avoided deforestation’), which is being discussed as an additional mechanism under the UN Framework Convention on Climate Change and its Kyoto Protocol, has the potential to alter the economic logic driving forest conversion.  相似文献   

Assimilation of sulfate and carbonaceous rocks: Experimental study,thermodynamic modeling and application to the Noril’sk-Talnakh region (Russia)     

《Ore Geology Reviews》2017

Most of the intrusions in the Noril’sk-Talnakh region (Siberia) are hosted in thick sedimentary sequences including abundant evaporitic and terrigenous sedimentary rocks. Three mafic-ultramafic intrusions in this region contain unusually thick massive sulfide deposits, which represent one of the world’s largest economic concentrations of Ni, Cu and PGE. The interaction of Siberian magmas with sulfate and organic matter-rich sedimentary rocks has been proposed as a possible mechanism for the origin of these exceptional sulfide deposits but the interaction process and the reaction paths have never been fully investigated. Here we clarify, by both experimental petrology and thermodynamic modeling, how sulfate and organic matter assimilation occur in mafic-ultramafic magmas, affecting magma composition, crystallization and sulfide saturation.Interaction experiments were conducted at conditions relevant to the emplacement of Noril’sk type intrusions (1200 °C, ∼80 MPa) to simulate the assimilation of sulfate and/or organic compounds by ultramafic magmas. We used a picrite from Noril’sk1 intrusion, and coal and anhydrite from the area as starting materials. The experimental results show that the incorporation of anhydrite into the magma occurs by chemical dissolution in the melt, which increases the magma’s sulfur content, but suppresses sulfide saturation and reduces olivine crystallization. Extreme assimilation leads to sulfate saturation in the magma and high dissolved sulfur contents of 0.9 ± 0.1 wt% S. Conversely, coal assimilation promotes sulfide segregation and magma crystallization, while decreasing the dissolved H₂O content of the melt and increasing the amount of coexisting fluid phase.We also employed gas-melt thermodynamic calculations to quantify the effect of these assimilations on the redox conditions and the S content of the magma, and investigate the role of temperature, pressure, and initial gas content of the magma in the assimilation process. We quantify how sulfate assimilation strongly oxidizes the magma and increases its S content; both effects are intensified by increasing pressure (from 50 to 100 MPa in this study), decreasing temperature (from 1350 to 1200 °C in this study), and decreasing amounts of fluid phase initially coexisting with the magma (from 2 to 0 wt%). The interaction with organic matter (CH in this study) induces a strong reduction of the magma, even for extremely low degrees of assimilation (few tenths of wt%), and the dehydration of the melt.We therefore suggest that in the Noril’sk-Talnakh district (1) additional S was supplied to mantle derived magmas by the assimilation of evaporitic rocks, and was transported during magma ascent in the form of dissolved, oxidized S; (2) a substantial reduction of the magma inducing sulfide segregation and important crystallization then occurred due to the interaction with carbonaceous sediments. This mechanism can potentially produce massive sulfide deposits by important sulfate assimilation (locally higher than 3 wt% CaSO₄) and minor organic matter assimilation (few tenths of wt% CH); however, if one of the two steps does not occur, or the assimilation in (1) is not large enough, disseminated sub economic or no sulfide deposits are produced. We conclude that exceptional conditions favoring substantial assimilation of sediments are needed to generate exceptional ore deposits like those of the Noril’sk-Talnakh district.  相似文献   

新疆乌苏泥火山地球化学特征及其泥浆源     

樊海龙  彭传凯  余心起  陈晶源  李江涛  乔东海  郭建明  许世阳 《地质通报》2017,36(8):1428-1438

泥火山是地质流体活动的结果,喷发需具备泥浆源、泥浆运移通道和水补给3个条件。对乌苏泥火山8个喷口泥浆进行岩石地球化学分析,轻稀土元素富集,重稀土元素亏损,轻、重稀土元素平均比值为6.81,泥浆中富集大离子亲石元素Ba、Rb等,高场强元素Nb、Ta强烈亏损,Th弱亏损,(La/Yb)_N值为5.47,Ce/La值为2.22,球粒陨石标准异常值δEu显示中等负异常(0.760~0.805);Sr/Ba值为0.33~1.01(平均值0.60),表明源岩为陆相沉积且古盐度较低,Ce/La(2.22)、Ce_(anom)(-0.007)、V/(V+Ni)(0.78)值均指示源岩形成于还原环境。稀土、微量元素分析及地层对比分析表明,乌苏泥火山源岩来自于下侏罗统八道湾组、三工河组,为河流沼泽相-半深湖相含煤地层代表的弱还原-还原沉积环境,源岩的最大埋藏深度为7~8km。泥火山源岩的研究为指示油页岩、烃类物质的位置提供了证据。  相似文献   

三山岛金矿床载金硫化物特征及其地质意义   总被引：7，自引：1，他引：6  

徐九华  谢玉玲  韩屹  李前懋 《华南地质与矿产》2004,(1):1-6

三山岛金矿床和焦家金矿床虽然均为“焦家式金矿”的典型代表,但两者的矿物共生组合、载金硫化物矿物成分特点、金矿物的成色,以及围岩蚀变类型、强度,矿化阶段的发育情况等都有明显的差异。三山岛金矿床的毒砂、砷黝铜矿含量较高,黄铜矿的Cu／Fe、方铅矿的Pb／S也较高。这些特征与三山岛金矿的多金属硫化物阶段更发育的事实一致,反映了该矿床可能在矿床(或矿体)分带方面表现了比焦家金矿较浅部较外围的特征,这对深部远景具有指示意义。  相似文献   

Helium, neon and argon isotope compositions of fluid inclusions in massive sulfides from the Jade hydrothermal field, the Okinawa Trough     

ZENG Zhigang  QIN Yunshan  ZHAI Shikui 《海洋学报(英文版)》2004,23(4):655-661

Helium, neon and argon isotope compositions of fluid inclusions have been measured in massive sulfide samples from the Jade hydrothermal field in the central Okinawa Trough. Fluid-inclusion 3He/4He ratios are between 6.2 and 10. l times the air value (Ra), and with a mean of 7.8Ra, which are consistent with the mid-ocean ridge basalt values [3He/^4He≈(6Ra- 11Ra)]. Values for ^20Ne/^22Ne are from 10.7 to 11.3, which are significantly higher than the atmospheric ratio (9.8). And the fluid-inclusion ^40Ar/^36Ar ratios range from 287 to 334, which are close to the atmosperic values (295.5). These results indicate that the noble gases of trapped hydrothermal fluids in massive sulfides are a mixture of mantle- and seawater-derived components, and the helium of fluid inclusions is mainly from mantle, the nelium and argon isotope compositions are mainly from seawater.  相似文献   

改善太湖马山水厂水源区水质的物理-生态工程实验研究   总被引：22，自引：7，他引：15  

濮培民 《湖泊科学》1993,5(2):171-180

以太湖无锡市马山水厂水源区的实验工程为例,论述了改善湖泊饮用水源水质的物理-生态工程的原理和效益。工程原则上能适用于不同的水深、水质、底泥和风浪条件。在两年实验中,工程技术和管理不断改进完善,经受住了多次大风浪考验。工程能有效地削减进入自来水厂水源的藻类,除藻率平均达59—78％以上。工程对TN、TP、NH_4~+-N、BOD_5、COD_(Mn)浊度的降低率分别为24—45％、2—24％、5—70％、9—61％、10—25％和9—40％。采用特殊技术后风眼莲可在有大风浪的大水面生长,其夏季生产力507g/(m~2·d),净化水质和抑制藻类生长作用显著。可降低处理自来水的氯耗量,并使外湖藻害基本上不成为用水高峰时增加产水量的限制因素,从而以更好更多的自来水满足日益增长的用水需要。  相似文献   

Mineralogy,geochemistry, and sulfur isotope characteristics of sediment-hosted hydrothermal sulfide minerals from the southern Okinawa Trough     

Yamin Yang  Zhigang Zeng  Xuebo Yin  Xiaoyuan Wang  Shuai Chen  Haiyan Qi  Zuxing Chen  Bowen Zhu 《海洋学报(英文版)》2021,40(10):129-143

Studies of the mineralogy and sulfur isotope composition of sediment-hosted hydrothermal sulfide minerals in cores are important for understanding the seafloor mineralization environment and material source and reconstructing the hydrothermal history. However, the source of ore-forming materials and the history of hydrothermal activity in the southern Okinawa Trough (SOT) remain unclear. Here, the mineralogy and sulfur isotope characteristics of sulfides from gravity core HOBAB4-S2, collected between the Yonaguni Knoll IV hydrothermal field (HF) and the Tangyin HF, was investigated. Enrichments in Zn (up to 321×10?6), Cu (up to 73.7×10?6), and Pb (up to 160×10?6) and the presence of pyrite, galena, pyrrhotite and minor sphalerite and chalcopyrite provide evidence for the input of hydrothermal materials into the sediments. The pyrite morphologies include disseminated cubic, pentagonal dodecahedron, and framboidal forms. Except for minor framboidal pyrite, euhedral pyrite from core HOBAB4-S2 is mainly of hydrothermal origin with Co/Ni ratios >1 and S/Fe atomic ratios <2 in the Cu-Zn-Pb-rich layers. The occurrences of hexagonal pyrrhotite, high-Co (up to 0.17%) pyrite and high-Fe sphalerite indicate that the hydrothermal precipitates formed at medium-high temperatures and low-sulfur fugacity (fS₂) environments. The δ34S values of sulfides (0.21‰–3.45‰) with low- fS₂ mineral assemblages (e.g., pyrrhotite ± high-Fe sphalerite) in the core are significantly lower than those of magmatic rocks and seawater, indicating possible incorporation of previously formed biogenic sulfur in the sediment. Combined with the age model of the core, it is suggested that hydrothermal activity likely began in the Tangyin HF before AD 1445–1483 and that at least three active episodes may have occurred since then.  相似文献   

低聚羧甲基壳聚糖的抗氧化性能   总被引：1，自引：0，他引：1  

孙涛  银旭红  姚倩  周冬香  邵则淮 《海洋科学》2010,34(2):54-56

将低聚壳聚糖(chitosan oligosaccharide,COS)醚化得到O-羧甲基壳聚糖(O-carboxymethyl chito-sanolig osaccharide,O-CMCOS)和N-羧甲基壳聚糖(N-carboxymethyl chitosanolig osaccharide,N-CMCOS),其取代度(substituting degree,DS)均为0.54,用红外光谱对其结构进行表征。同时,考察了其结构对超氧阴离子的清除活性以及还原能力。结果表明,COS及其衍生物清除超氧阴离子的活性及还原能力的强弱顺序均为:O-CMCOSCOSN-CMCOS。  相似文献   

海底热液硫化物——深海采矿前沿探索   总被引：1，自引：0，他引：1  

丁六怀  陈新明  高宇清 《海洋技术学报》2009,28(1)

结合深海采矿的现状,以海底热液硫化物这一潜在开采对象为基础,对国内外的相关研究与开发动态情况进行了介绍,分析了海底热液硫化开采远景,在剖析海底热液硫化物开采研究现实意义的基础上,提出海底热液硫化物是我国海洋采矿发展的新契机.并建议相关部门结合大洋战略逐步完善我国深海基础机电产品及工程装备研发体系.结合海底热液硫化物探测技术的发展,同步开展开采系统的前期研究工作,从而引导并推进我国深海采矿及海洋工程技术的发展.  相似文献