Dolphin noises recorded by echo‐sounder

The ultrasonic signals of dolphins show as “interference noise” on an echo‐sounder record. Some records obtained from Delphinus delphis in Hauraki Gulf, New Zealand, suggest that these emissions were being used for echo‐ranging, a phenomenon well established by previous work. Possible uses of such records in studying dolphin behaviour are explained.     

Airborne geophysical characterization of geotectonic relationships in the southern Ribeira Belt,Luís Alves Craton,and northern Dom Feliciano Belt,Brazilian Shield

ABSTRACT

In many Precambrian provinces, the understanding about the tectonic history is restrained by the limited exposure of rocks so that aerogeophysical data can provide information below the surface cover of sediments, soil, and water to build a tectonic model of the region. However, the tectonic evolution of cratons and shear zones is very complex due to scarce aerogeophysical and geological data. The integrated observation of geology, aerogammaspectrometry, and aeromagnetometry of the Brazilian Shield, states of Santa Catarina, Paraná, and southern São Paulo, is enhanced by a 2011 high-resolution aerogeophysical survey. The Ponta Grossa and Florianópolis dike swarms show two sets of linear high magnetic signal. Peralkaline–carbonatitic complexes are observed in all images, e.g. Jacupiranga, Tunas, and Anitápolis. Three main geotectonic provinces are apparent in the shield. The Dom Feliciano Belt has two domains in terms of radioelements K, Th, and U. This belt includes granitic rocks of the Florianópolis Batholith, Brusque Group schists, and Itajaí Basin of sedimentary and volcanic rocks. The Luís Alves Craton has mostly the Santa Catarina Granulitic Complex and other gneisses. The craton has patches of high emission rates and extends to the northeastern extreme of the studied area with a high-contrast magnetic signal in most of the unit. The Ribeira Belt also has high in gammaspectrometric images, although less homogeneous than the Dom Feliciano Belt. This belt contains granitic complexes, gneisses, and schists and has a low magnetic signal with patches of high analytical signal amplitude. Shear zones delimit different geotectonic units, but are also significant in the Ribeira Belt. The Luís Alves Craton is the most complex unit, as seen in ternary K + eTh + eU images, requiring the future discrimination of small features. This novel study of the Brazilian Shield based on new geophysical data supports the classification of the proposed main geotectonic units.     

Keene Basalt,northwest Officer Basin,Western Australia: tectonostratigraphic setting and implications for possible submarine mineralisation

GSWA Lancer 1, drilled in the northwest Officer Basin, intersected 49 m of tholeiitic basalt lava flows between depths of 527 and 576 m. These lavas have been named the Keene Basalt and were erupted during deposition of the shallow-marine Kanpa Formation, a mixed carbonate – siliciclastic succession in the Neoproterozoic Buldya Group. No direct dating of the Keene Basalt has been undertaken. Maximum depositional age constraints for the enclosing Kanpa Formation are provided by youngest concordant detrital zircon ages of 779±6 Ma for sandstone 19 m below the basalt, and 725±11 Ma for sandstone at the top of the Kanpa Formation in another drillhole. Correlation of the Kanpa Formation with the Burra Group of the Adelaide Rift Complex on palaeontological and chemostratigraphic grounds suggests an age older than 700 Ma. Limited geochemical data indicate that the Keene Basalt is of continental origin and shows a close similarity to mafic dykes near Mingary in South Australia. Petrographic and XRD analyses show that the Keene Basalt has been hydrothermally altered by interaction with seawater, and locally contains disseminated sulfides. Massive and disseminated sulfide mineralisation, similar to that of submarine systems, may exist in this tectonostratigraphic setting in the northwest Officer Basin.     

集约用地视角东北三省城市收缩效应诊断与作用机理研究

位处城镇化快速发展阶段的中国,在全球化与区域一体化浪潮中涌现了一批收缩城市、且这种趋势尚在不断加剧,引发了学术界对收缩城市发展效应的探索。本文从城市集约用地视角,结合城市土地集约度指标（城市收缩效应越显著、土地集约度越低,城市收缩效应越不显著、土地集约度越高）,以城市收缩最具代表性和典型性的东北三省为例、运用比较归纳分析法对2010—2019年间东北三省收缩城市的集约用地收缩效应及其阶段性、类型性和空间分布特征进行了诊断与揭示。结果表明：(1)东北三省15个收缩城市存在集约用地的收缩效应及其类型性和阶段性发展特征,对应的土地集约度平均得分呈现出：“非收缩城市>收缩城市、综合型收缩城市>资源依赖型收缩城市>虹吸型收缩城市>区位制约型收缩城市、收缩初期城市>收缩中期城市>收缩后期城市”的发展特征;(2)土地集约格局与城市收缩识别的空间分布具有高度一致性：集约度低等级城市全部属于收缩城市、集约度高等级城市属于非收缩城市,整体呈现出“核心-外围”+“南高北低”的空间特征;(3)城市收缩是发展要素流失→城市发展能力削弱、空间生产效率降低的结果,通过“投入-产出...     

Comparison of the basalt copper deposits in the Keweenaw Peninsula of michigan (USA) and the adjacent area of Yunnan-Guizhou Provinces (China)EI北大核心CSCD

After years of prospecting and mining of the basaltic copper deposits in the border area of Yunnan-Guizhou provinces, many people think the potential of metallogenic prospect is dismay and the deposits are of small sized. However, some researchers proposed in 2002 that these deposits have characteristics similar to those of the Keweenaw copper deposits, and thus their significance is worthy of further consideration. To investigate the resource potential in the region, we carried out a comparative study of the deposits in the two regions. The results show that the existence of redbed may be an important facor controlling the potential of copper mineralization. Therefore, we suggest that the native copper mineralization in the mid-low Triassic sandrocks demands further investigation and it is promising for metallogenic prospecting. ©, 2015, Science Press. All right reserved.     

How does landscape structure influence catchment transit time across different geomorphic provinces?

Despite an increasing number of empirical investigations of catchment transit times (TTs), virtually all are based on individual catchments and there are few attempts to synthesize understanding across different geographical regions. Uniquely, this paper examines data from 55 catchments in five geomorphic provinces in northern temperate regions (Scotland, United States of America and Sweden). The objective is to understand how the role of catchment topography as a control on the TTs differs in contrasting geographical settings. Catchment inverse transit time proxies (ITTPs) were inferred by a simple metric of isotopic tracer damping, using the ratio of standard deviation of δ¹⁸O in streamwater to the standard deviation of δ¹⁸O in precipitation. Quantitative landscape analysis was undertaken to characterize the catchments according to hydrologically relevant topographic indices that could be readily determined from a digital terrain model (DTM). The nature of topographic controls on transit times varied markedly in different geomorphic regions. In steeper montane regions, there are stronger gravitational influences on hydraulic gradients and TTs tend to be lower in the steepest catchments. In provinces where terrain is more subdued, direct topographic control weakened; in particular, where flatter areas with less permeable soils give rise to overland flow and lower TTs. The steeper slopes within this flatter terrain appear to have a greater coverage of freely draining soils, which increase sub‐surface flow, therefore increasing TTs. Quantitative landscape analysis proved a useful tool for inter‐catchment comparison. However, the critical influence of sub‐surface permeability and connectivity may limit the transferability of predictive tools of hydrological function based on topographic parameters alone. Copyright © 2009 John Wiley & Sons, Ltd.     

辽吉地区含硼岩系中斜长角闪岩地球化学

辽吉地区古元古界含硼岩系经过了中高级区域变质和混合岩化作用,主要由黑云母变粒岩、浅粒岩、电气石变粒岩、斜长角闪岩及富镁质含矿岩石组成,局部形成层状混合花岗岩。斜长角闪岩在含硼岩系内各个岩组中都有分布,岩石化学分析显示斜长角闪岩具有富钠、富镁、高铁、高钛特征,MgO含量成多众数值分布,辽东地区斜长角闪岩MgO含量高于集安地区,并且各类斜长角闪岩中硼含量都较高。辽东地区B、Cr、Ni明显高于集安地区,显示为海相地幔岩浆岩特征更为明显,集安地区则显示为变质热液改造特征。辽东地区斜长角闪岩的稀土地化显示为热液改造的幔源岩浆特征,集安地区的斜长角闪岩的稀土地化显示为壳源沉积岩特征。含硼岩系斜长角闪岩与浅粒岩稀土配分模式相似,表明部分斜长角闪岩与浅粒岩具有岩浆成因特征,而电气变粒岩、黑云变粒岩与混合岩稀土富集模式显示海相沉积泥岩变质成因,混合岩化及变质热液对原岩具有明显改造作用。斜长角闪岩石的地球化学特征表明原岩环境为富钠、富硼的海相环境,原岩主要是海相富镁拉斑玄武岩和海相泥质岩。     

碱性岩相关铜-金(钼)矿床的研究进展

由于超过20%的大型-超大型铜-金(钼)矿床与碱性岩浆有关,因此,该类矿床引起矿床学家的广泛关注。碱性岩有关的铜-金矿床的成矿岩体、物化条件及围岩种类各具特色,成矿成因类型多样,主要的成因类型为斑岩型铜-金(钼)、浅成低温热液脉型金-铜(钼)。总体上,该类矿床的矿化和蚀变具有一定的特征:该类矿床多产出在伸展环境下、均富碲化物矿化、有大量的钾质交代作用、含有氟矿物质和钒云母等,成矿蚀变亦有一定的规律。长英质岩石中经常发生钾长石蚀变,而绢云母、碳酸盐和钾长石的混合蚀变常出现在中基性侵入岩中,水热合成石英和酸性蚀变十分罕见。这种特征矿化可能与碱性岩浆流体演化有关,这种流体富含CO_2,且在高氧逸度、低硫逸度条件下释放。在伸展背景下的碱性-钙碱性省寻找此类矿床具有巨大的勘查潜力,尤其在碱性岩体中心及其外围可能形成勘探的靶区。在中国与碱性岩有关的金矿床亦有广阔的找矿前景,在借鉴国外寻找此类矿床经验的同时,仍需加强对与矿化作用有关的岩浆体活动的研究。     

浙闽地区下白垩统黑色泥岩沉积环境初探:微体古生物与有机地球化学证据

在中国东南沿海浙闽地区的中生代火山岩分布区,广泛发育有中生代沉积岩系,关于这套沉积岩是否受到海水作用影响,目前还存在争论。通过对福建下白垩统坂头组（K1b）、浙江地区为寿昌组（K1s）和馆头组（K1g）地层进行系统观察及采样,并进行详细的古生物化石观察及有机地球化学研究,发现该区沉积岩中除陆相高等植物之外,还见过渡相的线叶植物和海相红藻和褐藻化石;同时某些有机地球化学特征亦显示其具有一定的海相沉积特征,如普遍存在较高的伽马蜡烷含量,伽马蜡烷/C30藿烷比值较低（0.11～0.18,平均值0.14）,以及C30重排藿烷检出。因此,从古生物学与有机地球化学特征来看,该区的确受到海侵作用影响,结合地质背景,推测海侵事件主要受古太平洋域的影响。     

Mantle thermal structure and active upwelling during continental breakup in the North Atlantic

Seismic reflection and refraction data acquired on four transects spanning the Southeast Greenland rifted margin and Greenland–Iceland Ridge (GIR) provide new constraints on mantle thermal structure and melting processes during continental breakup in the North Atlantic. Maximum igneous crustal thickness varies along the margin from >30 km in the near-hotspot zone (<500 km from the hotspot track) to 18 km in the distal zone (500–1100 km). Magmatic productivity on summed conjugate margins of the North Atlantic decreases through time from 1800±300 to 600±50 km³/km/Ma in the near-hotspot zone and from 700±200 to 300±50 km³/km/Ma in the distal zone. Comparison of our data with the British/Faeroe margins shows that both symmetric and asymmetric conjugate volcanic rifted margins exist. Joint consideration of crustal thickness and mean crustal seismic velocity suggests that along-margin changes in magmatism are principally controlled by variations in active upwelling rather than mantle temperature. The thermal anomaly (ΔT) at breakup was modest (100–125°C), varied little along the margin, and transient. Data along the GIR indicate that the potential temperature anomaly (125±50°C) and upwelling ratio (4 times passive) of the Iceland hotspot have remained roughly constant since 56 Ma. Our results are consistent with a plume–impact model, in which (1) a plume of radius 300 km and ΔT of 125°C impacted the margin around 61 Ma and delivered warm material to distal portions of the margin; (2) at breakup (56 Ma), the lower half of the plume head continued to feed actively upwelling mantle into the proximal portion of the margin; and (3) by 45 Ma, both the remaining plume head and the distal warm layer were exhausted, with excess magmatism thereafter largely confined to a narrow (<200 km radius) zone immediately above the Iceland plume stem. Alternatively, the warm upper mantle layer that fed excess magmatism in the distal portion of the margin may have been a pre-existing thermal anomaly unrelated to the plume.