Morphology of HCN and CN in Comet Hale-Bopp (1995 O1)

We compare images of Comet Hale-Bopp (1995 O1) in HCN and CN taken near perihelion (April 1, 1997) to determine the origin of CN in comets. We imaged the J=1→0 transition of HCN at λ=3 mm with the BIMA Array. Data from two weeks around perihelion were summed within four phase bins based on the rotational period of the comet. This increases both the signal-to-noise ratio and the u-v coverage while decreasing the smearing of the spatial features. The similarly phased narrowband CN images were taken at Lowell Observatory within the same range of dates as the HCN images. We find that there is a better correlation between HCN and CN than between HCN and the optically dominant dust. If the CN in jets does have a dust source it would have to have a very low albedo and/or small particle size. The production rates are consistent with HCN being a primary parent of CN, although there are discrepancies between the HCN destruction scalelength and the CN production scalelength which we discuss.     

Bald kelp: natural and harvesting-induced frond loss in the South African kelp Ecklonia maxima

Ecklonia maxima dominates kelp beds on the west coast of southern Africa, and is commercially and ecologically valuable. Some plants lose all their secondary blades (fronds), leaving only the gas-filled bulb and short primary blade at the top of the stipe. These ‘bald’ kelps may persist for months or longer, occupying substratum space but contributing little to productivity. We investigated natural causes of balding in five kelp beds in False Bay, South Africa, and the effect of simulated commercial frond-harvesting on loss of fronds. Densities of sporophytes with and without fronds were measured at the water surface during low tides. Generalised linear modelling analysis showed a significant relationship between balding and site (whether sheltered from or exposed to swell/wind), position in the kelp bed (shoreward or seaward) and total E. maxima density. We conclude that balding is caused mainly by drying of meristematic basal regions of fronds during emersion of kelp heads at low tide. After partial harvesting of fronds, kelp heads floated higher out of the water, but after 95 days frond loss was significantly higher only when fronds were cut too close to the primary blade, possibly because of damage to meristematic tissue. Nevertheless, increased emersion that results from frond-harvesting may increase desiccation and blade loss and we suggest caution in setting harvest limits for this kelp.     

桐柏碰撞造山带及其邻区变形特征与构造格局

桐柏碰撞造山带及其邻区可以划分为九个大地构造单元,自北向南分别是:华北克拉通南缘岩石构造单元——宽坪岩群、具弧后盆地性质的二郎坪岩石构造单元、具岛弧性质的秦岭杂岩单元、龟山岩组和南湾岩组构成的俯冲前缘楔构造带、构造混杂岩带、桐柏北部高压岩片单元、桐柏核部杂岩单元、桐柏南部高压岩片单元以及随州构造变形带。根据详细的构造解析以及新的地质年代学资料,本文将中生代以来的构造变形划分为五幕,前两幕变形主要发育在构造混杂岩带以南的各个岩石构造单元中,之后的三幕变形则波及整个研究区。第一幕变形的时间约为255～238Ma,以发育区域上透入性的片理及北西西向的拉伸线理为主,并导致了高压岩片早期自西向东的挤出。第二幕变形的时间约为230～215Ma,以自北向南的逆冲推覆构造为主,使得高压岩片进一步垂向抬升。第三幕变形应早于下侏罗统,以近北西西向的宽缓褶皱为主要特征,该幕变形期间桐柏核部杂岩及其两侧高压岩片单元发生同步的抬升。第四幕变形大致发生在140～130Ma之间,主要表现为桐柏核部杂岩两侧走滑型韧性剪切带的活动,桐柏核部杂岩表现出向东的挤出。第五幕变形发生在120～80Ma,表现为北西向及北东向的脆性断裂活动,并切割以上所有构造形迹。桐柏高压岩片的抬升剥露受多幕变形控制,呈阶段性的抬升。     

陕西省略阳县杨家坝多金属矿区成矿作用地球化学示踪

本文以陕西省略阳县杨家坝多金属矿区为例,通过对该矿区岩(矿)石和各类脉体的岩相学、稀土和微量元素及流体包裹体地球化学示踪发现,多金属中重晶石的形成及硅化、碳酸盐化、滑石化、纤闪石化、绢云母化和绿泥石化和透闪石岩的含氟浅闪石及隐晶硅质玻璃和微晶硅质,这表明与成矿蚀变有关的热液流体是一种不同于一般地壳流体的富硅、钛、铁、碱质和挥发份,并具备熔体性质的成矿流体。各类样品的稀土元素配分模式明显富集LREE,在Ce、Eu、Yb异常的组合上也各具特征。LREE富集是地幔流体作用的显著特征之一;矿石和脉体的负Ce、正Eu和负Yb异常以及流体包裹体中H2O-C6H6成分,是高温还原地幔流体的重要标志;正Ce和负Eu异常的出现,以及Ce、Eu、Yb异常的减弱和消失则是壳幔混染叠加改造的显示。综合研究表明:矿区成矿过程可能统一受制于秦岭地区碰撞造山背景下具高温还原性质的地幔流体作用,且由此引发壳幔强烈混染的叠加改造作用在成矿过程中发挥了重要作用。     

Analyses of dust coma morphology of Comet Hyakutake (1996 B2) near perigee: outburst behavior, jet motion, source region locations, and nucleus pole orientation

We present inner-coma dust imaging of Comet Hyakutake (1996 B2) obtained on 11 consecutive nights in late March 1996, an interval including a major outburst and the comet’s closest approach to Earth. The evolution of the outburst morphology is followed, along with the motion along the tail of several outburst fragments. Two spiral dust jets—a primary jet, along with a much weaker secondary jet—are visible throughout the interval and are produced by two source regions on a rotating nucleus. These are examined as a function of rotational phase and viewing geometry, with their appearance changing from a nearly face-on view on March 18 to side-on by March 28. The dust outflow velocity as a function of distance from the nucleus is derived, with the dust continuing to accelerate to a distance of 4000 km or more and reaching an average outflow velocity of 0.38 km s⁻¹ between 3000 and 8000 km. We present details of our Monte Carlo modeling of the jets and our methodology of fitting the model to the images. The modeling yields the pole orientation of the nucleus, with an obliquity of approximately 108°, corresponding to an RA of 13^h41^m and a Dec of −1.1°. For an assumed spherical nucleus, the primary active region is centered at approximately −66° latitude, has a radius of about 56°, and therefore covers about 22% of the surface. The source of the secondary jet is at a latitude of −28°, has a radius of about 16°, and is located at a longitude nearly 180° away from the primary source. Estimated uncertainties for the pole orientation and the source locations and sizes are each about 3°. This solution for the nucleus orientation and source locations explains the strong asymmetry in measured production rates before and after perihelion in radio observations (Biver et al., 1999, Astron. J. 118, 1850-1872). The modeling also tightly constrains the sidereal rotation period as 0.2618 ± 0.0001 day, completely consistent with the expected +0.0003 day difference from the observed solar rotation period of 0.2614 ± 0.0004 day determined by Schleicher and Osip (2002, Icarus 159, 210-233), given the pole orientation and position of the comet in its orbit.     

Photometry and Imaging of Comet C/2000 Wm1 (Linear)

Earth, Moon, and Planets -     

Sulfur Chemistry at Millimeter Wavelengths in C/Hale-Bopp

The recent availability of bright comets has given us an excellent opportunity to study cometary chemistry. Comet Hale-Bopp (1995 O1)gave us the particularly rare opportunity to study a bright and active comet for almost two years. Our program concentrated on millimeter-wave observations of sulfur-bearing molecules in an effort to understand the total sulfur budget of the comet. Using the National Radio Astronomy Observatory 12-m telescope on Kitt Peak we monitored both the long and short-term variations in H₂S, CS, and OCS, as well as observing H₂CS and SO. This was the first observation of H₂CS in any comet (Figure 1). Additionally, we mapped CS with the BIMA interferometer. Variations in the line profiles and changes in line intensity as large as a factor of two were seen in day to day observations of both H₂S and CS. An example for H₂S is shown in Figure 2. This is the first time we can attempt to study the entire group of sulfur-bearing molecules. Models of the sulfur coma have thus far largely been based on observations of the daughter products CS and atomic sulfur made over the last 18 years using the International Ultraviolet Explorer (IUE) satellite, coupled with radio observations of CS and H₂S in several recent comets. Four new sulfur-bearing species have been observed in comets Hale-Bopp and Hyaku take, three of them parent species. The high resolution maps in CS will also allow spatial information to be included in the sulfur model for the first time. C/Hale-Bopp is the first comet in which so many sulfur species have been observed. Analysis of the abundances of these species in comparison to the total atomic sulfur observed should reveal whether or not we can now account for all of the primary sulfur sources in comets. Perhaps the most interesting question that these observations raised was why C/Hale-Bopp appeared to contain so much more SO and SO₂ (as observed by others) than any other comet. This spurred the discovery that the UV fluorescence models of these species were incorrect (S. J. Kim, this issue). Analysis of the data and modeling of the sulfur budget are still underway. This revised version was published online in July 2006 with corrections to the Cover Date.     

Bio-treatment and water reuse as feasible treatment approaches for improving wastewater management during flotation of copper ores

Established and emerging technologies for treatment of flotation wastewaters are compared and discussed in the context of their applicability during the management of wastewaters from Cu–Co ores processing through flotation in the Katanga province of the Democratic Republic of Congo. The effects from water recycling on water quality and flotation performance are briefly presented in parallel. The ore processing schemes and the wastewater management practices at two operational concentrators are illustrated as study cases and their peculiarities outlined. A reference to a copper concentrator in a nearby Zambia is addressed for comparative purpose. Based on analysis of the findings, the clarification, bio-treatment inside the tailing ponds or the use of constructed wetlands as polishing stage prior to water reuse are suggested as feasible treatment approaches in view improving the management practice of flotation wastewaters during the dressing of copper ores in the Katanga province.     

中国东南部晚中生代构造伸展作用——来自海南岛基性岩墙群的证据

论文在系统地分析了海南岛文市、叉河、三亚地区的三处基性岩墙群的LA-ICP-MS锆石U-Pb年代学和元素地球化学特征的基础上,探讨了岩墙群的来源和其反映的地球动力学背景。文市岩墙群形成于约101Ma,叉河和三亚岩墙群形成于约93Ma;主量元素化学特征显示它们属碱性系列,微量元素化学特征为富集轻稀土元素和大离子亲石元素(Sr、K、Rb、Ba、Th),亏损高场强元素(Nb、Ta、Ti);Sr-Nd同位素组分显示其源区具有EMⅡ特征。这两期岩墙群的存在,显示了海南岛地区在早白垩世晚期和晚白垩世早期存在两次构造伸展事件。海南岛90Ma左右的岩墙群与广东、福建同时代的岩墙群构成中国东南沿海90Ma广泛发育的、呈近北北东向展布的岩墙群带,它们具有相同成因机制,指示中国东南部在90Ma左右时经历了强烈区域性拉张作用;这些岩墙群虽来源于不同的地幔源区,但均与俯冲流体交代作用有关。