Retrograde alteration of chromian kyanite in metachert and amphibolite whiteschist from the Southern Alps,New Zealand,with implications for uplift on the Alpine Fault

Chromian kyanites with a maximum content of 2.88 wt.% Cr₂O₃ occur in metachert and amphibolite from the Southern Alps, New Zealand. The presence of the whiteschist assemblage kyanite-talc, together with kyanite-zoisite assemblages in calc silicate bands imply high pressure metamorphism, with climactic conditions of approximately 10 kb at 650°–700° C. Mylonitization caused by a change to oblique-slip movements on the Alpine Fault is succeeded by retrograde alteration of kyanite-bearing assemblages. Kyanite is pseudomorphed by Cr-margarite-fuchsite-Cr-zoisite assemblages in metachert and by less chromian margarite and zoisite in amphibolite. Contemporaneously hornblende and phlogopite break down to chlorite. Subsequently the metachert pseudomorphs are mantled by muscovite and those in amphibolite by anorthite and chromite. The breakdown of margarite and zoisite to anorthite implies decompression under a low thermal gradient, compatible with almost isothermal uplift on the Alpine Fault. Late stage retrograde products include fibrous kyanite (probably forming by recrystallization of primary alluminosilicate) and scapolite (possibly orginating through interaction of Cl-bearing fluids in a geothermal system).In the Southern Alps there is a significant uplift following the Cretaceous Rangitata Orogeny, probably in the order of 11–15 km. However, the bulk of the uplift, approximately 25 km, took place in the past 10 m.y. during Kaikoura Orogenic uplift on the Alpine Fault. It is during this latest and continuing phase of uplift that the sequence of kyanite alteration reactions occurred.     

Incorporating uncertainty of future sea-level rise estimates into vulnerability assessment: A case study in Kahului, Maui

Accurate sea-level rise (SLR) vulnerability assessments are essential in developing effective management strategies for coastal systems at risk. In this study, we evaluate the effect of combining vertical uncertainties in Light Detection and Ranging (LiDAR) elevation data, datum transformation and future SLR estimates on estimating potential land area and land cover loss, and whether including uncertainty in future SLR estimates has implications for adaptation decisions in Kahului, Maui. Monte Carlo simulation is used to propagate probability distributions through our inundation model, and the output probability surfaces are generalized as areas of high and low probability of inundation. Our results show that considering uncertainty in just LiDAR and transformation overestimates vulnerable land area by about 3 % for the high probability threshold, resulting in conservative adaptation decisions, and underestimates vulnerable land area by about 14 % for the low probability threshold, resulting in less reliable adaptation decisions for Kahului. Not considering uncertainty in future SLR estimates in addition to LiDAR and transformation has variable effect on SLR adaptation decisions depending on the land cover category and how the high and low probability thresholds are defined. Monte Carlo simulation is a valuable approach to SLR vulnerability assessments because errors are not required to follow a Gaussian distribution.     

成熟勘探矿集区新一轮找矿：勘查战略创新及铜陵矿集区找矿实例

成熟勘探的矿集区非常有必要开展新一轮的找矿，但矿床模式的局限和大埋藏深度等困难制约了这些地区的预测性找矿发现。促进其预测性找矿发现的关键战略包括：勘查模型的创新、勘查技术的创新和各种信息的综合集成预测。勘查模型的创新必须包含基于地球动力学剖析的新成矿概念，动力学数值模拟是有效的创新手段之一；勘查技术创新的主要目的是加大探测深度和提高探测与解释的准确性，必须以详细可靠的地质资料为基础；综合信息集成是利用GIS和知识驱动及数据驱动的方法充分提取各种数据中的有用信息，集成为更加可靠的预测图。在这种思想的指导下，我们在铜陵凤凰山矿田进行了预测和勘查，并成功地发现了深部的隐伏矿床。     

Late Pleistocene–Holocene environmental and climatic history of a freshwater paramo ecosystem in the northern Andes

This study presents the first multi-proxy palaeoenvironmental and palaeoclimatic history for northern South America based on the palaeolimnological reconstruction of a pond located in a dry paramo at 3570 masl. During the Last Glacial Maximum (LGM), the study area was under glacial conditions, then during global events Heinrich Stadial 1 (HS1), Bølling–Allerød (BA), and the Younger Dryas (YD), the pond expanded, accumulation rates and proxies for erosion reached the highest values, indicative of humid conditions, with maxima in humidity during the BA and YD. Dry conditions and pond desiccation occurred in the Greenlandian–Northgrippian and by 6010 cal a bp the area was transformed into the mire of today. Comparisons with records from other sites in South America indicate that changes in humidity are most likely controlled by the Intertropical Convergence Zone, mainly during the glacial and postglacial, and by changes in the Pacific Ocean, more pronounced after the YD.     

A luminescence‐based chronology for the Harletz loess sequence,Bulgaria

The Harletz loess‐palaeosol sequence is located in northwestern Bulgaria and represents an important link between well‐studied loess sequences in eastern Romania and further sites to the west of the Carpathians (e.g. Serbia and Hungary). The aim of this study was to establish a chronostratigraphy of the deposits, using various methods of luminescence dating, together with basic stratigraphical field observations as well as magnetic properties. Luminescence dating was carried out using the quartz fine grain fraction and a SAR protocol, and the feldspar coarse grain fraction, applying the MET‐pIRIR protocol. Due to underestimation of the quartz fine grain fraction in the lower parts of the sequence, the resulting chronology is mainly based on the feldspar ages, which are derived from the stimulation temperature at 150 °C. A comparison with nearby sequences from Serbia, Hungary and Romania, and interpretations obtained through the stratigraphical and sedimentological signature of the sequence, supports the established chronology. Our data suggest that the prominent palaeosol (soil complex) in the upper quarter of the sequence was formed during MIS 5. It would follow that large parts of the Last Glacial loess overlying this palaeosol were probably eroded, and that the thick loess accumulation underlying this soil complex can be allocated to the penultimate glacial (MIS 6). A prominent MIS 6 tephra, which has been reported from other sequences in the area, is also present at Harletz.     

The GIS approach to evaporite-karst geohazards in Great Britain

Evaporite karst in Great Britain has formed in Permian and Triassic gypsum, and in Triassic salt. Active dissolution of these deposits can occur on a human rather than a geological timescale causing subsidence and building damage. The British Geological Survey has taken two approaches towards understanding and advising on hazards caused by dissolution of these soluble rocks. At a detailed level, a national database and GIS of karstic features is being populated. Information gathered includes dolines, springs, stream sinks, caves and building damage. At a national level, the soluble rocks in Great Britain have been identified and digital-map polygon information relating to them was extracted from the British 1:50,000-scale digital geological map. These areas have been assessed, and in places their margins extended to include some overlying rocks where subsidence features are known to penetrate upwards through the overlying sequence. The national areas have then been assessed using detailed local information to assign a susceptibility rating from A (extremely low) to E (high), depending on the nature and regularity of the subsidence events that occur. This national zonation of the soluble rocks can be used for planning, construction and in the insurance businesses. This has proved useful for assessing the potential stability of linear routes, such as roads and pipelines or for other important structures such as bridges and buildings. The information can also be used to delineate zones of karstic groundwater flow.     

Bowers Swell: Evidence for a zone of compressive deformation concentric with Bowers Ridge, Bering Sea

Bowers Swell is a newly discovered bathymetric feature which is up to 90 m high, between 12 and 20 km wide, and which extends arcuately about 400 km along the northern and eastern sides of Bowers Ridge. The swell was first revealed on GLORIA sonographs and subsequently mapped on seismic reflection and 3.5 kHz bathymetric profiles. These geophysical data show that the swell caps an arcuate anticlinal ridge, which is composed of deformed strata in an ancient trench on the northern and eastern sides of Bowers Ridge. The trench fill beneath the swell is actively deforming, as shown by faulting of the sea floor and by thinning of the strata across the crest of the swell. Thinning and faulting of the trench strata preclude an origin for the swell by simple sediment draping over an older basement high. We considered several models for the origin of Bowers Swell, including folding and uplift of the underlying trench sediment during the interaction between the Pacific plate beneath the Aleutian Ridge and a remnant oceanic slab beneath Bowers Ridge. However, such plate motions should generate extensive seismicity beneath Bowers Ridge, which is aseismic, and refraction data do not show any remnant slab beneath Bowers Ridge. Another origin considered for Bowers Swell invokes sediment deformation resulting from differential loading and diapirism in the trench fill. However, diapirism is not evident on seismic reflection profiles across the swell. We favour a model in which sediment deformation and swell formation resulted from a few tens of kilometers of low seismicity motion by intraplate crustal blocks beneath the Aleutian Basin. This motion may result from the translation of blocks in western Alaska to the south-west, forcing the movement of the Bering Sea margin west of Alaska into the abyssal Aleutian Basin.