Low‐temperature thermochronology of the Mt Painter Province,South Australia

Apatite fission track results are reported for 26 outcrop samples from the Mt Painter Inlier, Mt Babbage Inlier and adjacent Neoproterozoic rocks of the northwestern Curnamona Craton of South Australia. Forward modelling of the data indicates that the province experienced variable regional cooling from temperatures >110°C during the Late Palaeozoic (Late Carboniferous to Early Permian). The timing of this cooling is similar to that previously reported from elsewhere in the Adelaide Fold Belt and the Curnamona Craton, suggesting that the entire region underwent extensive Late Palaeozoic cooling most likely related to the waning stages of the Alice Springs or Kanimblan Orogenies. Results from the Paralana Fault Zone indicate that the eastern margin of the Mt Painter Inlier experienced a second episode of cooling (～40–60°C) during the Paleocene to Eocene. The entire region also experienced significant cooling (less than ～40°C) during the Late Cretaceous to Palaeogene in response to unroofing and/or a decrease in geothermal gradient. Regional cooling/erosion during this time is supported by: geomorphological and geophysical evidence indicating Tertiary exhumation of at least 1 km; Eocene sedimentation initiated in basins adjacent to the Flinders and Mt Lofty Ranges sections of the Adelaide Fold Belt; and Late Cretaceous ‐ Early Tertiary cooling previously reported from apatite fission track studies in the Willyama Inliers and the southern Adelaide Fold Belt. Late Cretaceous to Palaeogene cooling is probably related to a change in stress field propagated throughout the Australian Plate, and driven by the initiation of sea‐floor spreading in the Tasman Sea in the Late Cretaceous and the Eocene global plate reorganisation.     

Mary Kathleen metamorphic‐hydrothermal uranium — rare‐earth element deposit: Ore genesis and numerical model of coupled deformation and fluid flow

The Mary Kathleen U‐REE orebody of the Proterozoic Mt Isa Block was the product of chemical and physical interaction between regional metamorphic/hydrothermal fluids and preexisting calcic skarns. The deposit provides excellent examples of mechanical control on ore localisation and of the complexity of ores in rocks with protracted thermal histories. Host skarns were produced by contact metasomatism around the 1740 Ma Burstall Granite, whereas the allanite‐uraninite ore formed under amphibolite‐facies conditions, late during the D₂ phase of the ca 1550–1500 Ma Isan orogeny. Observations of ore geometry are consistent with previous geochronologic data demonstrating a large time gap between skarn formation and ore genesis. Numerical modelling of coupled deformation and fluid flow suggests that veins at the core of ore shoots may have formed as tensile or shear fractures during coupling of the competent skarn host with the late‐D₂ Mary Kathleen Shear Zone, allowing a change of orientation of ore shoots with distance from the shear zone. Mineral chemistry and petrographic observations suggest the possible role of a redox control on chemical localisation of ore by conversion of Fe²⁺‐rich clinopyroxene‐rich skarn host to Fe³⁺‐rich secondary garnet ‘skarn’ and uraninite‐allanite ore. Alternately, fluid pressure drops as a consequence of fracturing of the host skarn may have triggered fluid unmixing, or fluid mixing, leading to ore precipitation. Available data do not allow clear definition of the ultimate source of the U and REE, nor of the specific chemical ore‐forming mechanism. However, regional constraints, previous Sm–Nd modelling, and our numerical models suggest a combination from proximal skarn hosts and from distal sources accessed by flow of metamorphic and/or late tectonic igneous‐derived fluids. The deposit has some similarities with ironstone‐hosted Cu–Au ± U deposits found in the nearby Cloncurry Belt.     

龙首山地块的归属问题:来自地壳结构和中—新元古代地层的证据

为了弄清楚龙首山地块的归属问题,对龙首山地块地壳结构和地层特征进行研究,发现龙首山地块具有由结晶基底和沉积盖层组成的双层地壳结构。该地块结晶基底由龙首山群组成,龙首山群岩性主要为一套条带状、眼球状混合岩夹斜长角闪岩、花岗质片麻岩、黑云斜长片麻岩等,普遍经历了角闪岩相区域变质作用。龙首山地块缺失长城系、青白口系和南华系,下部沉积盖层由蓟县系墩子沟群和震旦系顶部的烧火筒沟组构成。墩子沟群经历了埋藏变质作用,粉砂岩具千枚状构造,砂岩有一定程度的重结晶,地层层理保存完整。烧火筒沟组上部为含砾千枚岩、粉砂质千枚岩,下部为冰碛砾岩,冰碛砾岩总与寒武系含磷层相伴出现。地壳整体结构与华北克拉通基本特征相同,而扬子克拉通具有结晶基底、褶皱基底和沉积盖层3层地壳结构,与华北克拉通和龙首山地块迥异。因此,龙首山地块应归属于华北克拉通。     

Response of a mid‐latitude cirque glacier to climate over the last two decades: Mangaehuehu Glacier,Mt Ruapehu

The recent loss of mountain glaciers in response to climate warming has been reported across a range of latitudes globally, but the processes involved are not always straightforward. In southern Pacific mid‐latitudes, twentieth‐century glacier fluctuations are thought to reflect the strength of westerly atmospheric circulation, which brings increased precipitation, leading to mass gains. We present a study of the response of Mangaehuehu Glacier, a cirque glacier on Mt Ruapehu, to climate over the last two decades. Glacier surface area fluctuated in size over this period, corresponding closely with mean end‐of‐summer snowlines in the Southern Alps. The key control on glacier extent appears to be ablation season temperature, itself controlled by regional atmospheric circulation, including El Niño‐Southern Oscillation, Interdecadal Pacific Oscillation (IPO), and to a lesser extent, Southern Annular Mode (SAM). Copyright © 2011 John Wiley & Sons, Ltd.     

On the Relationship between Local Topography and Small Glacier Change under Climatic Warming on Mt. Bogda, Eastern Tian Shan, China

Glacial features in the geological record provide essential clues about past behavior of climate. Of the numerous physical systems on earth, glaciers are one of most responsive to climate change, especially small glaciers, their direct marginal response taking only a few years or decades to be expressed. Accelerating recession of modern glaciers raises the issue of the climate’s impact on water runoff. Data based on topographic maps and Advanced Spaceborne Thermal Emission and Radiometer (ASTER) imagery sho...     

云南黎明高山丹霞地貌成因及其演化模式

始新统红色磨拉石建造和裂隙网奠定黎明丹霞地质景观条件,岩石中富含各种致色元素,使丹霞峰林赤壁呈现多种颜色;内外动力共同作用,形成黎明地区分布范围广、极具独特性的高山丹霞地貌单体形态和组合形态。高山丹霞地貌的形成与演化,可分为四个主要阶段。     

以全球参照系为基准的珠峰地区重力场

珠穆朗玛峰位于欧亚板块和印度板块边缘的碰撞地带 ,地壳运动活跃 ,地形复杂。三十余年来 ,我国曾单独或与国外合作在珠穆朗玛峰及其北部毗邻地区进行了五次 (196 6、1975、1992、1998和 1999年 )大规模的大地测量工作 ,其中包括天文、重力、平面、高程和气象等测量工作。根据这些大地测量成果以全球参照系为基准 ,对该地区的重力场进行了研究。提出了适用于该地区的推估重力异常、垂线偏差和高程异常的最佳技术方案和相应成果     

安徽大别山南麓柑桔冻害分布模式的研究

本文将地形因子参数化,建立了柑桔冻害低温与测点海拔高度、遮蔽度、山体遮蔽长度和地势倾斜度之间的数量关系。     

西藏南迦巴瓦峰地区第四纪环境探讨

本文根据西藏南迦巴瓦峰地区第四纪沉积物特征和孢粉分析结果,讨论了环境变化问题。指出,中更新世以来南峰地区抬升约2000—3000米,全新世抬升约600米,并对气候变化作了论述。     

四川龙门山区早泥盆世Emsian期群落古环境分析

通过对群落特征生物构造、生态习性、成活曲线、赋存围岩沉积及群落构成内容等特征分析,本文认为四川龙门山区Emsian期地层已经识别的以腕足动物为主的八个底栖群落生态位集中于B.A.3,少数可归入B.A.2,其相当的沉积环境主要为浅海内陆棚相、台地生物礁相。