Pre- and post-drill comparison of the Mount Elbert gas hydrate prospect, Alaska North Slope

In 2006, the United States Geological Survey (USGS) completed a detailed analysis and interpretation of available 2-D and 3-D seismic data, along with seismic modeling and correlation with specially processed downhole well log data for identifying potential gas hydrate accumulations on the North Slope of Alaska. A methodology was developed for identifying sub-permafrost gas hydrate prospects within the gas hydrate stability zone in the Milne Point area. The study revealed a total of 14 gas hydrate prospects in this area.In order to validate the gas hydrate prospecting protocol of the USGS and to acquire critical reservoir data needed to develop a longer-term production testing program, a stratigraphic test well was drilled at the Mount Elbert prospect in the Milne Point area in early 2007. The drilling confirmed the presence of two prominent gas-hydrate-bearing units in the Mount Elbert prospect, and high quality well logs and core data were acquired. The post-drill results indicate pre-drill predictions of the reservoir thickness and the gas-hydrate saturations based on seismic and existing well data were 90% accurate for the upper unit (hydrate unit D) and 70% accurate for the lower unit (hydrate unit C), confirming the validity of the USGS approach to gas hydrate prospecting. The Mount Elbert prospect is the first gas hydrate accumulation on the North Slope of Alaska identified primarily on the basis of seismic attribute analysis and specially processed downhole log data. Post-drill well log data enabled a better constraint of the elastic model and the development of an improved approach to the gas hydrate prospecting using seismic attributes.     

景区依托型旅游村与核心景区耦合发展研究

旅游村作为新型乡村旅游地,是国家乡村旅游＂百千万工程＂中最基础的组成部分。从景区依托型旅游村的视角出发,选取黄山山岔村与黄山风景区作为案例地,运用多元回归分析方法,对两者之间耦合发展进行研究。结果显示：（1）黄山风景区发展大力提升了山岔村社会经济文化水平;（2）黄山风景区发展对村落环境影响较小;（3）黄山风景区发展对村落社区参与有影响,但并不显著。从景区与村落的发展特征出发,较为系统地揭示景区依托型旅游村与核心景区耦合发展的内在动力源于位差潜势、催化潜势、管理潜势和多稳定潜势,这些形成了景村耦合发展的演化机制。在此基础上,提出了景村耦合发展的4条途径。     

Permian

Summary Late in the Carboniferous Period or early in the Permian ice covered much of Tasmania (Fig. 30b). The sub‐Permian surface had a relief of several thousand feet with particularly low areas near Wynyard and Point Hibbs and high areas near Cradle Mountain, Devonport, Deloraine, Wylds Crag and Ida Bay and a peninsula in eastern Tasmania (Fig. 30a).

The glaciers from an ice centre north‐west of Zeehan diverged about a higher area near Cradle Mountain. One tongue occupied a deep valley near Wynyard and a lobe fanned out south of the high area to occupy parts of northern and central Tasmania and to override some parts of the east coast peninsula.

West of Maydena the ice scoured shell beds and dumped the shell fragments in the till on the Styx Range. Thus the base of the ice may well have been below sea‐level. Carey and Ahmad (1961) suggested that the Wynyard Tillite was deposited below a “wet‐base” glacier. David (1908, p. 278) suggested deposition from “land ice in the form of a piedmont or of an ice‐sheet” but that near Wynyard the ice came down very close to, if not actually to, sea‐level. The extent of the glaciation and the distribution of erratics of western Tasmanian origin in eastern Tasmania make it seem likely that either a piedmont glacier or an ice‐sheet rather than mountain glaciation was involved.

Following retreat of the glaciers the sea covered the till, probably to a considerable depth, eustatic rise of sea‐level being much more rapid than isostatic readjustment.

The Quamby Group is underlain by or passes laterally into thin conglomerates and sandstones in a number of places, but most of the group appears to be of deep water, partially barred basin origin. Marine oil shales accumulated close to islands. Shallowing of the sea during deposition of the upper part of the Quamby Group seems to be indicated by the fauna and increasing sandiness in marginal areas. Instability in the source areas is shown by the presence of turbidity current deposits in the higher parts of the group. The Golden Valley Group, of Upper Sakmarian and perhaps Lower Artinskian age, was deposited in a shallower sea than the Quamby Group but the deposits are more extensive along the east coast peninsula and on the flanks of the Cradle Mountain island. This anomaly may be explained if the rate of deposition exceeded the rate of rise of sea‐level. The sediments of the Golden Valley Group became finer‐grained upwards in most parts of Tasmania probably indicating reduction in relief of the source area. Some instability is indicated by turbidity current deposits. Uplift of source areas in north‐western Tasmania early in Artinskian time resulted in the spreading of sand over the shallow silts of the Golden Valley Group onto the east coast peninsula and over the Cradle Mountain area. The sand formed a wide coastal plain containing lakes and swamps and the sea was restricted to a small gulf in southern Tasmania during the deposition of the lower part of the Mersey Group. During deposition of this group the sea rose once to form a long, narrow gulf extending as far north as Port Sorell and then retreated. This inundation resulted in the development of two cyclothems in many parts of Tasmania.

A little later in Lower Artinskian time the sea rose and covered most of Tasmania except perhaps the far north‐west. This wide transgression probably resulted from down‐warping as an eustatic rise in sea‐level would be expected to produce thickest deposition over the old gulf in southern Tasmania and along the axis of Mersey Group inundation but the zone of thickest Cascades Group crosses these at a high angle. During deposition of the Cascades Group marine life became very abundant in the shallow sea over which a few icebergs floated. During the Artinskian tectonic instability increased as shown by the increasing number of turbidites in the upper part of the Grange Mudstone and the lower part of the Malbina Formation. The sea became less extensive and the source areas in north‐western and north‐eastern Tasmania were uplifted. The zone of thickest deposition of the Malbina Formation trended north‐north‐westerly. The rapid succession of turbidity currents killed the benthonic fauna and it was only during deposition of the upper part of the formation possibly in Lower Kungurian time that life became abundant again in the Hobart area. The sea spread a little over the east coast peninsula and further instability is recorded in the Risdon Sandstone. The resulting turbidity currents killed the benthonic fauna and it never became properly established again in any part of Tasmania during the Permian. A wide shallow sea covered much of Tasmania and was bordered by low source areas during deposition of the Ferntree Group. The axis of greatest thickness had an almost meridional trend and lay west of that of the Malbina Formation. Late in the Permian, probably in the Tartarian, rejuvenation of the source areas, particularly in western Tasmania, and withdrawal of the sea, resulted in deposition of sands and carbonaceous silts of the Cygnet Coal Measures. The zone of greatest thickness was almost parallel to but west of that of the Ferntree Group.

The thickness of the Permian System and the sheet‐like character of many of the members and formations suggest shelf rather than geosynclinal deposition. The average rate of deposition was of the order of 1 ft. in ten thousand years (about 0–003 mm./annum). However, the sediments differ markedly from those on stable shelves in that many of them are poorly‐sorted. Some of the poor sorting may be attributed to deposition from drifting icebergs but some is due to tectonic instability.

Uplift and downwarping and movement of zones of maximum thickness have been deduced above and it is probable that the tectonic instability started as early as Lower Artinskian and it may have started during Sakmarian (upper part of Quamby Group). Maximum instability seems to have occurred in Middle or Upper Artinskian time (Malbina Formation) and it is probably significant that this was a time of considerable orogenic movement in New South Wales (part of the Hunter‐Bowen Orogeny, Osborne, 1950). Progressive westward movement of zones of maximum thickness of units in Upper Permian time seems to have occurred and this again is reminiscent of the situation at the time in New South Wales (Voisey, 1959, p. 201) but seems to have started later. Uplift and development of a major synclinal structure with a trend approximately north‐north‐westerly occurred late in Permian time.     

Mount Woolnough: the submerged volcano,SE of Sydney,NSW

Part of a larger investigation of the sea bed off Sydney was a study of the extinct submarine volcano Mount Woolnough. It is located approximately 41 km east of Kurnell, NSW, and protrudes 175 m above the sediment cover at depths of approximately ?550 to ?375 m. Volcanic rock, approximately 2.2 km in diameter, is exposed above the sediment sea floor and is much smaller than its magnetic expression (approximately 13 km in diameter). Samples dredged from Mount Woolnough were conglomerates with phosphatic nodules and volcanic fragments set in a fine foraminiferal sediment matrix. Zircons within the mafic fragments yielded a minimum age of 261 Ma.     

Coupled Process Models of Fluid Flow and Heat Transfer in Hydrothermal Systems in Three Dimensions

Geothermal fields and hydrothermal mineral deposits are manifestations of the interaction between heat transfer and fluid flow in the Earth’s crust. Understanding the factors that drive fluid flow is essential for managing geothermal energy production and for understanding the genesis of hydrothermal mineral systems. We provide an overview of fluid flow drivers with a focus on flow driven by heat and hydraulic head. We show how numerical simulations can be used to compare the effect of different flow drivers on hydrothermal mineralisation. We explore the concepts of laminar flow in porous media (Darcy’s law) and the non-dimensional Rayleigh number (Ra) for free thermal convection in the context of fluid flow in hydrothermal systems in three dimensions. We compare models of free thermal convection to hydraulic head driven flow in relation to hydrothermal copper mineralisation at Mount Isa, Australia. Free thermal convection occurs if the permeability of the fault system results in Ra above the critical threshold, whereas a vertical head gradient results in an upward flow field.     

FHD-1矢量质子磁力仪与温度相关性分析

通过矢量质子磁力仪FHD-1各分量北京时21点数据、日均值数据和室内记录的温度值作相关性分析,探讨温度对线圈和产出的数据是否有影响。     

Using amphibole phenocrysts to track vapor transfer during magma crystallization and transport: An example from Mount St. Helens,Washington

In order to evaluate and further constrain models for volatile movement and vapor enrichment of magma stored at shallow levels, amphibole phenocrysts from 2004–2005 Mount St. Helens dacite were analyzed for major and selected trace elements (Li, Cu, Zn, Mn, and REE) and Li isotopes. Several recent studies have examined fluid-mobile trace element abundances in phencryst phases and melt inclusions as a means of tracking volatile movement within subvolcanic magmatic systems, and high Li contents in plagioclase phenocrysts from 1980 and 2004 Mount St. Helens dacites have been interpreted as evidence that shallow magma was fluxed by a Li-bearing vapor phase prior to eruption.     

Simulation of the 1980 eruption of Mount St. Helens using the ash-tracking model PUFF

The dispersal of volcanic ash from the May 18, 1980 eruption of Mount St. Helens (MSH) has been simulated using the Lagrangian ash-tracking model PUFF. Previous applications of the model were limited to smaller, short-lived eruptions with ash dispersal occurring mainly within the troposphere. Two high-resolution atmospheric reanalysis datasets (ERA-40 and NCEP/NCAR-40) allowed MSH ash cloud dispersal to be simulated up to 30 km elevation. The 1980 eruption was divided into two distinct eruptive phases, (1) an initial, relatively short-lived blast/surge phase that injected ash up to 30 km and (2) a subsequent nine-hour plinian phase that maintained an average eruption column height of 16 km. Using PUFF, the two phases of the MSH eruption were modeled separately based on a range of individual input parameters and then combined to produce an integrated simulation of the entire eruption. The trajectory and areal extent of the modeled atmospheric ash cloud best match the actual distribution of MSH ash when input parameters are set to values inferred from satellite and radar data collected on May 18, 1980. The prevailing wind field exerts the strongest control on the advection and ultimate position of the modeled ash cloud, making the maximum column height and the vertical distribution of ash the most sensitive of the PUFF input parameters for this event. The results indicate that the PUFF model works well at simulating the dispersal of ash injected well into the lower stratosphere from a moderate, relatively long-lived eruption, such as MSH. However, attempts to use PUFF to recreate some granulometric aspects of the MSH fallout deposit, such as the maximum particle size as a function of distance from source, were not successful. PUFF consistently predicts much greater fallout distances for small ash particles (< 500 µm) than actually observed in the MSH deposit. The effective settling velocities used by the PUFF model appear to be too slow to accurately predict fallout distances of small ash particles. As a consequence the PUFF model may overestimate the duration of ash loading in the atmosphere associated with the distal fine ash component of explosive eruptions.     

Simulations of the 2004 lava flow at Etna volcano using the magflow cellular automata model

Since the mechanical properties of lava change over time, lava flows represent a challenge for physically based modeling. This change is ruled by a temperature field which needs to be modeled. MAGFLOW Cellular Automata (CA) model was developed for physically based simulations of lava flows in near real-time. We introduced an algorithm based on the Monte Carlo approach to solve the anisotropic problem. As transition rule of CA, a steady-state solution of Navier-Stokes equations was adopted in the case of isothermal laminar pressure-driven Bingham fluid. For the cooling mechanism, we consider only the radiative heat loss from the surface of the flow and the change of the temperature due to mixture of lavas between cells with different temperatures. The model was applied to reproduce a real lava flow that occurred during the 2004–2005 Etna eruption. The simulations were computed using three different empirical relationships between viscosity and temperature.     

Hazards from pyroclastic density currents at Mt. Etna (Italy)

Despite the recent recognition of Mount Etna as a periodically violently explosive volcano, the hazards from various types of pyroclastic density currents (PDCs) have until now received virtually no attention at this volcano. Large-scale pyroclastic flows last occurred during the caldera-forming Ellittico eruptions, 15–16 ka ago, and the risk of them occurring in the near future is negligible. However, minor PDCs can affect much of the summit area and portions of the upper flanks of the volcano. During the past ~ 20 years, small pyroclastic flows or base-surge-like vapor and ash clouds have occurred in at least 8 cases during summit eruptions of Etna. Four different mechanisms of PDC generation have been identified during these events: (1) collapse of pyroclastic fountains (as in 2000 and possibly in 1986); (2) phreatomagmatic explosions resulting from mixing of lava with wet rock (2006); (3) phreatomagmatic explosions resulting from mixing of lava with thick snow (2007); (4) disintegration of the unstable flanks of a lava dome-like structure growing over the rim of one of the summit craters (1999). All of these recent PDCs were of a rather minor extent (maximum runout lengths were about 1.5 km in November 2006 and March 2007) and thus they represented no threat for populated areas and human property around the volcano. Yet, events of this type pose a significant threat to the lives of people visiting the summit area of Etna, and areas in a radius of 2 km from the summit craters should be off-limits anytime an event capable of producing similar PDCs occurs. The most likely source of further PDCs in the near future is the Southeast Crater, the youngest, most active and most unstable of the four summit craters of Etna, where 6 of the 8 documented recent PDCs originated. It is likely that similar hazards exist in a number of volcanic settings elsewhere, especially at snow- or glacier-covered volcanoes and on volcano slopes strongly affected by hydrothermal alteration.