Passive Seismic Monitoring of Mine-scale Geothermal Activity: A Trial at Lihir Open Pit Mine     

X. Luo  A. Creighton  J. Gough 《Pure and Applied Geophysics》2010,167(1-2):119-129

The Lihir open pit mine in Papua New Guinea is located inside an old volcano where geothermal activity is strongly present. Outbursts of hot water and steam into the mining areas were a major safety concern. Passive seismic monitoring was carried out at the mine to investigate whether the geothermal activities could be detected and located using microseismic techniques in a mining environment. In this trial, sixteen triaxial geophones which can withstand temperature up to 200°C were used and installed in four deep boreholes inside the pit. The microseismic events were discriminated using the STA/LTA triggering criterion. During 6 weeks of monitoring, more than 17,000 events were recorded. Approximately 12% of the events showed harmonic vibration characteristics similar to those observed in other geothermal and volcanic areas, suggesting that the geothermal activity inside the pit was captured by the microseismic monitoring system. More than 75% of the events present both P and S waves and they were interpreted to be associated with rock fracturing due to stress release near the bottom of the pit. Many geothermal-type events were located in areas where shear events occurred, implying that the detected geothermal events were not far from the mining area below the pit and they may also be associated with mining. The borehole installation of the geophones significantly reduced the interference of mining noise and achieved good observation of the seismic events. However, equipment installation requires great attention as the geophones may be destroyed due to unexpected rising temperature within the boreholes.  相似文献   

A primer in gibbs energy minimization for geophysicists     

J. A. D. Connolly 《Petrology》2017,25(5):526-534

Gibbs energy minimization is the means by which the stable state of a system can be computed as a function of pressure, temperature and chemical composition from thermodynamic data. In this context, state implies knowledge of the identity, amount, and composition of the various phases of matter in heterogeneous systems. For seismic phenomena, which occur on time-scales that are short compared to the timescales of intra-phase equilibration, the Gibbs energy functions of the individual phases are equations of state that can be used to recover seismic wave speeds. Thermodynamic properties relevant to modelling of slower geodynamic processes are recovered by numeric differentiation of the Gibbs energy function of the system obtained by minimization. Gibbs energy minimization algorithms are categorized by whether they solve the non-linear optimization problem directly or solve a linearized formulation. The former express the objective function, the total Gibbs energy of the system, indirectly in terms of the partial molar Gibbs energies of phase species rather than directly in terms of the Gibbs energies of the possible phases. The indirect formulation of the objective function has the consequence that although these algorithms are capable of attaining high precision they have no generic means of treating phase separation and expertise is required to avoid local minima. In contrast, the solution of the fully linearized problem is completely robust, but offers limited resolution. Algorithms that iteratively refine linearized solutions offer a compromise between robustness and precision that is well suited to the demands of geophysical modeling.  相似文献   

The luminosity-weighted or 'marked' correlation function     

Ramin Skibba  Ravi K. Sheth  rew J. Connolly  Ryan Scranton 《Monthly notices of the Royal Astronomical Society》2006,369(1):68-76

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Petrology of titanian clinohumite and olivine at the high-pressure breakdown of antigorite serpentinite to chlorite harzburgite (Almirez Massif,S. Spain)   总被引：1，自引：0，他引：1  

V.?López Sánchez-VizcaínoEmail author  V.?Trommsdorff  M.?T.?Gómez-Pugnaire  C.?J.?Garrido  O.?Müntener  J.?A.?D.?Connolly 《Contributions to Mineralogy and Petrology》2005,149(6):627-646

Rocks of the Cerro del Almirez ultramafic massif (Sierra Nevada, Betic Cordillera, S. Spain) record the high-pressure dehydration of antigorite–olivine serpentinite to form chlorite harzburgite (ol + opx + chl). In the field, these two rock types are separated by a well-defined isograd. Titanian clinohumite (TiCl) and olivine show textural and compositional differences depending on the rock type. OH–TiCl occurs in the serpentinite as disseminated grains and in veins. F–OH–TiCl is observed exclusively in the chlorite harzburgite, where it occurs as porphyroblastic grains and within prograde olivine as irregular and lamellar, planar intergrowths at microscopic and submicroscopic scales. Petrological evidence of partial to complete breakdown of TiCl to olivine + ilmenite is preserved in both rock types. Chlorite harzburgite is characterized by a brown pleochroic olivine with abundantally oriented microscopic to submicroscopic oxide particles. The mean Ti-content of the brown olivine is 144 ppm. The brown olivine preserves TiCl lamellae that sometimes grade into ghost lamellae outlined by the oxide trails. This observation suggests that some of the oxide inclusions in the brown olivine are derived from the breakdown of TiCl intergrowths. Thermodynamic modelling of selected Almirez bulk rock compositions indicates a temperature increase from 635°C to 695°C, at pressures ranging from 1.7 GPa to 2.0 GPa, as the cause for the compositional adjustment of TiCl between the Almirez antigorite serpentinite and chlorite harzburgite. These P–T estimates are in good agreement with the sequence of phase relations observed in the field. The computed phase diagrams in conjunction with the geothermal conditions envisaged for different subduction settings indicate that TiCl is stable in the vicinity of the antigorite serpentinite/chlorite harzburgite phase boundary in some subduction settings. In these circumstances, clinohumite–olivine intergrowths in chlorite harzburgite may act as a sink for high field strength elements, and probably other elements, that are present in the mantle–wedge fluids.  相似文献   

A coupled petrological–tectonic model for sedimentary basin evolution: the influence of metamorphic reactions on basin subsidence     

K. Petrini  J. A. D. Connolly  & Yu. Yu. Podladchikov 《地学学报》2001,13(5):354-359

The lithosphere is subject to fluctuations in temperature and pressure during the formation of sedimentary basins. These fluctuations cause metamorphic reactions that change the density of the lithosphere, which, in turn, influences basin subsidence. This contribution develops a model for sedimentary basin formation to assess the importance of this coupling. The model shows that basin subsidence is significantly affected by metamorphic densification. Compared to results obtained with cruder density models, metamorphic densification accelerates subsidence in the initial post-rifting stages as garnet becomes stable over an increasing depth interval within the mantle, an effect that amplifies the crust–mantle density contrast. For models with an extraordinarily cold lithosphere, uplift is generated as a late stage of basin evolution. In general, subsidence is not smooth but occurs instead in small steps reflecting periods of accelerated/decelerated subsidence. For typical crustal thicknesses, subsidence is controlled largely by reactions in the mantle, and particularly those determining garnet stability.  相似文献   

Dario Grana,Tapan Mukerji,and Philippe Doyen: Seismic Reservoir Modeling: Theory,Examples, and Algorithms     

Connolly  Patrick Alexander 《Mathematical Geosciences》2021,53(7):1697-1698

Mathematical Geosciences -  相似文献   

Modeling effects of climate change on Yakima River salmonid habitats     

James R. Hatten  Thomas R. Batt  Patrick J. Connolly  Alec G. Maule 《Climatic change》2014,124(1-2):427-439

We evaluated the potential effects of two climate change scenarios on salmonid habitats in the Yakima River by linking the outputs from a watershed model, a river operations model, a two-dimensional (2D) hydrodynamic model, and a geographic information system (GIS). The watershed model produced a discharge time series (hydrograph) in two study reaches under three climate scenarios: a baseline (1981–2005), a 1-°C increase in mean air temperature (plus one scenario), and a 2-°C increase (plus two scenario). A river operations model modified the discharge time series with Yakima River operational rules, a 2D model provided spatially explicit depth and velocity grids for two floodplain reaches, while an expert panel provided habitat criteria for four life stages of coho and fall Chinook salmon. We generated discharge-habitat functions for each salmonid life stage (e.g., spawning, rearing) in main stem and side channels, and habitat time series for baseline, plus one (P1) and plus two (P2) scenarios. The spatial and temporal patterns in salmonid habitats differed by reach, life stage, and climate scenario. Seventy-five percent of the 28 discharge-habitat responses exhibited a decrease in habitat quantity, with the P2 scenario producing the largest changes, followed by P1. Fry and spring/summer rearing habitats were the most sensitive to warming and flow modification for both species. Side channels generally produced more habitat than main stem and were more responsive to flow changes, demonstrating the importance of lateral connectivity in the floodplain. A discharge-habitat sensitivity analysis revealed that proactive management of regulated surface waters (i.e., increasing or decreasing flows) might lessen the impacts of climate change on salmonid habitats.  相似文献   

Fate and Transport of Hydrophobic Organic Chemicals in the Lower Passaic River: Insights from 2,3,7,8-Tetrachlorodibenzo-p-Dioxin     

Peter H. Israelsson  James D. Quadrini  John P. Connolly 《Estuaries and Coasts》2014,37(5):1145-1168

The fate and transport of hydrophobic organic chemicals (HOCs) is particularly complex in estuaries because of bidirectional longitudinal currents, density stratification, the tendency to trap sediments, and significant dilution in the downstream bay or ocean. Investigations of HOCs in estuaries are further complicated because HOCs typically enter from multiple sources. The distribution of contaminants in estuarine sediment beds reflect a time integration of a complex balance of time- and space-variable fate and transport processes and loading history. A unique opportunity to study HOC fate and transport exists in the Lower Passaic River (LPR), where a pesticide manufacturer was the dominant source of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) to the estuary and the distribution of this “tracer of opportunity” provides insights about fate and transport processes in estuarine systems. This paper presents observed sediment 2,3,7,8-TCDD patterns within the LPR and the adjacent Newark Bay, and interprets them in terms of fate and transport processes that likely distributed the contaminant from its dominant source, drawing upon other physical datasets as needed. Major observations include that estuarine transport processes have distributed 2,3,7,8-TCDD approximately 18 km upstream of the source and downstream across Newark Bay, and that, generally, HOC trapping processes within the LPR have been highly effective, particularly near the 2,3,7,8-TCDD source and in downstream areas. The present LPR surface sediment 2,3,7,8-TCDD distribution indicates spatially variable recovery, which appears broadly driven by historical net sedimentation patterns, though the dominant processes may be shifting as the system continues to evolve.  相似文献   

Asteroid (101955) 1999 RQ36: Spectroscopy from 0.4 to 2.4 μm and meteorite analogs     

Beth Ellen Clark  Richard P. Binzel  Ellen S. Howell  Edward A. Cloutis  Maureen Ockert-Bell  Phil Christensen  Maria Antonietta Barucci  Francesca DeMeo  Dante S. Lauretta  Harold Connolly Jr.  Alicia Soderberg  Carl Hergenrother  Lucy Lim  Josh Emery  Michael Mueller 《Icarus》2011,216(2):462-475

We present reflectance spectra from 0.4 to 2.4 μm of Asteroid (101955) 1999 RQ36, the target of the OSIRIS-REx spacecraft mission. The visible spectral data were obtained at the McDonald Observatory 2.1-m telescope with the ES2 spectrograph. The infrared spectral data were obtained at the NASA Infrared Telescope Facility using the SpeX instrument. The average visible spectrum is combined with the average near-infrared wavelength spectrum to form a composite spectrum. We use three methods to constrain the compositional information in the composite spectrum of Asteroid (101955) 1999 RQ36 (hereafter RQ36). First, we perform a least-squares search for meteorite spectral analogs using 15,000 spectra from the RELAB database. Three most likely meteorite analogs are proposed based on the least-squares search. Next, six spectral parameters are measured for RQ36 and their values are compared with the ranges in parameter values of the carbonaceous chondrite meteorite classes. A most likely meteorite analog group is proposed based on the depth of overlap in parameter values. The results of the least-squares search and the parametric comparisons point to CIs and/or CMs as the most likely meteorite analogs for RQ36, and COs and CHs as the least likely. RQ36 has a spectrally “blue” continuum slope that is also observed in carbonaceous chondrites containing magnetite. We speculate that RQ36 is composed of a “CM1”-like material. Finally, we compare RQ36 to other B-type asteroids measured by Clark et al. (Clark, B.E. et al. [2010]. J. Geophys. Res. 115, E06005). The results of this comparison are inconclusive. RQ36 is comparable to Themis spectral properties in terms of its albedo, visible spectrum, and near-infrared spectrum from 1.1 to 1.45 μm. However, RQ36 is more similar to Pallas in terms of its near-infrared spectrum from 1.6 to 2.3 μm. Thus it is possible that B-type asteroids form a spectral continuum and that RQ36 is a transitional object, spectrally intermediate between the two end-members. This is particularly interesting because Asteroid 24 Themis was recently discovered to have H₂O ice on the surface (Rivkin, A., Emery, J. [2010]. Nature 464, 1322–1323; Campins, H. et al. [2010a]. Nature 464, 1320–1321).  相似文献   

Compositional evolution of the protoplanetary disk: Oxygen isotopes of type-II chondrules from CR2 chondrites     

Harold C. Connolly Jr.  Gary R. Huss 《Geochimica et cosmochimica acta》2010,74(8):2473-325

Chondrules are the dominant component of chondritic meteorites and attest to high-temperature transient heating events within the protoplanetary disk. They provide valuable constraint on the disk environments in which they formed and potentially the evolution of primitive planetary materials in the disk. The oxygen isotopic composition of CR2 chondrite type-II chondrules was investigated. Our data show significant variation in the isotopic compositions of the chondrules with no petrographic or geochemical means to identify what chondrule will plot where on a three-isotope diagram. Although we cannot rule out that these chondrules may have come from another chondrite-forming region, we argue in context of type-I chondrules from CR2 chondrites that CR2 type-II chondrules record changes in solid and gas composition during formation due to the vaporization of icy bodies in localized regions of the inner disk.  相似文献