Basement Temperature Research Articles

Contrasting thermal histories in the Dom Feliciano Belt triggered by magmatism related to the Paraná-Etendeka LIP and fracture zone proximity

The present-day southern Brazilian continental margin rests on top of the Dom Feliciano Belt (DFB) and adjacent cratons. This belt formed through the collision of the Rio de La Plata, Kalahari, Paranapanema, Congo and Luis Alves paleoplates in the Neoproterozoic. Several low-temperature thermochronology works were executed in the area, although none of them demonstrated how the basement temperature of the entire DFB evolved through time. To this end, this work aims to provide new Apatite Fission Track (AFT) and Apatite (UTh)/He (AHe) ages for samples collected in the Catarinense Shield, in the northern DFB, and to perform inverse modeling in those samples. Besides, the collection of the basement temperature of 128 locations across the entire belt and adjacent cratons provided thermal information to create inverse-distance weighted interpolation maps documenting the progression of the temperature from 360 to 30 Ma. New AFT ages range from 126.6 ± 24.1 to 60.3 ± 6.03 Ma, whereas AHe ages span from 153.0 ± 9.2 to 62.5 ± 3.7 Ma. Mean track lengths are short to medium, suggesting complete thermal annealing of apatite crystals. Apatite single-grain eU concentration range from 4.5 to 96 μg/g and display a sparse correlation with AHe ages. Interpolation maps evidence a contrasting temperature evolution of the northern DFB and bordering cratons relative to the southern segment and surrounding cratons. Near-surface exposure of the basement in the northern segment was possibly much earlier than in the south, followed by partial burial by the sedimentary successions of the Paraná Basin. The emplacement of volcanic rocks of the Paraná-Etendeka Large Igneous Province and associated dyke swarms and alkaline volcanic plugs related to the Florianópolis Fracture Zone raised and sustained higher basement temperatures until 30 Ma, resetting low-temperature thermochronometers in the northern DFB, which was minor to absent in the southern DFB.

Simulation of Naturally Ventilated Underground Car Park with CFD

Nowadays, the speed of urbanization is increasing rapidly, so the urban land area is fully utilized to build high-rise buildings, apartments, and commercial centers, and thus, the car tunnel parking and basement parking basements also become more popular. However, apartment fire and explosion, especially car fire and explosion is an extremely important issue that must be concerned in construction design. Therefore, it is essential to design an effective ventilation system in the parking basement when a fire occurs an effective ventilation system for the tunnel is really necessary for basement firefighting. When building up the car park, the importance is not only a reasonable architecture but also the ventilation and air quality of the tunnel because it directly affects human health. Decades ago, scientists had studied the solution to ventilate the car park. The computational fluid dynamics (CFD) method is also applied to determine the pressure and velocity intensity for buildings that detect residuals in architecture, thereby improving and providing a superior solution. More for this problem. Many studies related to this issue have been published internationally. Jiang (Jiang, Allocca, & Chen, 2004) also investigated natural ventilation by using Reynolds Averaged Navier - Stokes turbulence model (RANS). Khalil (Khalil, Shoukry, H.A, & Harridy, 2015) also examined the distribution of CO emissions from buses in a basement in Cairo using ANSYS FLUENT software.The basement car park is a popular solution to effectively use urban land, especially in commercial centers and apartments. However, the situation of apartment fire and explosion is a hot problem, partly due to the tunnel ventilation has not met the requirements of fire safety. Therefore, the design of the car park basement ensures fire safety as well as bring comfort to people. In this study, the problem of basement temperature and wind velocity by natural ventilation method will be analyzed and evaluated in accordance with ADPI standard and Carbon monoxide concentration with WHO standard to identify areas of unsatisfactory temperature and velocity to reasonably adjust and propose other suitable ventilation options.

Balancing Well 교차혼합 지중열교환기의 스마트 냉난방 히트펌프 시스템의 성능평가에 관한 연구

This study performed a single hole operation method using a balancing well-cross-mixed underground heat exchanger, and conducted thermal performance studies of an SCW-type underground heat exchanger using a two-well. The study attempted to change the existing operating method of the two adjacent SCW underground heat exchangers with one ball each. The SCW-type geothermal heat exchanger is considered to enable up to 20% of bleed discharge at maximum load, which makes groundwater usage unequal. The efficiency factor of the geothermal system was improved by constructing the discharged water by cross-mixing two balancing wells to prevent the discharge of groundwater sources and keep the temperature of the underground heat exchanger constant. As a result of the cooling and heating operation with the existing SCW heat exchange system and the balancing well-cross-mixed heat exchange system, the measured performance coefficient improved by 23% and 12% in cooling and heating operations, respectively. In addition, when operating with a balanced cross-mixing heat exchange system, it has been confirmed that the initial basement temperature is constant with a standard deviation of 0.08 to 0.12°C.

EXPERIMENTAL STUDY FOR GROUND TYPE EFFECT ON SOLAR CHIMNEY POWER PLANT

Solar chimney power plant is a technology capable to generate electric energy through a wind turbine using the solar radiation as energy source; nevertheless, one of the objectives pursued since its invention is to achieve energy generation during day and night. The ground under the power plant plays an important role on the energy balance and heat transfer, due to its natural behavior as a heat storage system. An experimental model was designed in Holley Kerbala city (Iraq), which consisted of a 3m collector radius with 8ᴼ collector inclination angle and a 6m height of chimney been constructed and collector periphery opening height 3cm. Three kinds of grounds was studied in this work: sand, mixed from sand and pebble and the third is black pebble. The results show that the highest airflow temperature inside the chimney reached was 66.8Co when using the black pebbles basement. The maximum basement temperature measured was 81.6Co for the mixed basement. Also, the highest temperature difference reached was 23.2Co for the same ground that have good performance during day light compared with pebble basement that have more energy saving in night.

The thermal influence on the consolidation state of underthrust sediments from the Nankai margin and its implications for excess pore pressure

The Nankai Trough convergent margin has been the focus of many multi-methodological surveys including half a dozen scientific deep-sea drilling expeditions. The boreholes focused on the smectite-dominated area off Cape Ashizuri and the thermally altered, illite-dominated region off Cape Muroto. On the basis of these surveys a number of studies addressed to the stress state of the underthrust sediments and its implications for the plate boundary thrust. Although the basement temperature has been found to be up to ∼ 110 °C, none of these studies drew close attention to temperature effects on the consolidation state of the sediments. To overcome this shortcoming, we selected end member sediment lithologies from the incoming oceanic plate in the Shikoku Basin and subjected them to elevated stresses and temperatures. We here present results from a series of heated (20 °C, 100 °C, 150 °C) uniaxial consolidation experiments up to effective normal stresses of ca. 70 MPa. The main finding is a positive correlation between temperature and pore space reduction. Based on in-situ temperature information from earlier scientific drilling, our study suggests that temperature has an influence on the consolidation state of underthrust sediments along the Nankai Margin. Together with secondary consolidation, thermal consolidation serves to explain steep log-linear consolidation curves of the incoming Lower Shikoku Basin sediments. The onset of diagenesis in this realm led to the transition of smectite to illite and to a different consolidation behaviour. Estimated in-situ pore pressures based on in-situ temperature data result in up to ∼ 1 MPa smaller overpressures than those previously estimated from drilling data alone. Those values, which imply underconsolidation at drill sites near the frontal Nankai accretionary complex, are further believed to facilitate frictional sliding along the subduction thrust.

Linking basement carbonate vein compositions to porewater geochemistry across the eastern flank of the Juan de Fuca Ridge, ODP Leg 168

Leg 168 of the Ocean Drilling Program (ODP) investigated the heat flow, fluid chemistry and crustal alteration associated with ridge flank hydrothermal systems. Ten sites were drilled on the eastern flank of the Juan de Fuca Ridge, along an 80 km transect, between 20 and 100 km east of the spreading centre. Recovered cores consisted of 100–500 m of sediment with shallow penetration (1.7–48.1 m) into the underlying igneous basement (0.8–3.6 Ma). Here we use the composition of calcium carbonate minerals, from veins within the upper basement, to reconstruct the evolving chemistry of hydrothermal fluids with increasing crustal age and sediment cover thickness. We show for the first time a clear link between the alteration of the basement rocks as recorded by secondary minerals, and the near-basement sedimentary pore fluids, which are often assumed to be representative of the basement fluids responsible for low temperature alteration of the upper crust. Carbonates precipitated from basement fluids that ranged in strontium isotopic composition from near-modern seawater ( 87Sr/ 86Sr≈0.70918) to the near-basement pore fluid values at any one site. 87Sr/ 86Sr ratios are independent of mineralogy with both aragonite and calcite precipitating from variably evolved fluids with the range in carbonate 87Sr/ 86Sr increasing with crustal age. A parallel geochemical evolution of basement fluids and sediment porewaters is shown since 87Sr/ 86Sr ratios of near-basement pore fluids decrease from 0.709013 to 0.707108 away from the ridge axis. A correlation exists between 87Sr/ 86Sr ratios and δ 18O-calculated fluid temperatures, with more geochemically evolved carbonates having precipitated from warmer fluids. Basement fluid compositions, calculated from carbonate Sr, Mg, Fe and Mn concentrations combined with suitable partition coefficients, are also temperature-dependent. Given an observed increase in basement temperature with age, from 16°C to 64°C along the transect, a progressive chemical development of basement fluid is demonstrated. Carbonate veins in volcanic basement from ODP Holes 504B and 896A, on the Costa Rica Rift, record the same temperature compositional evolution of basement fluid as those from the Juan de Fuca Ridge flank. Although these locations have different thermal histories and therefore must have experienced different temporal geochemical evolution of basement fluid, basement temperature appears to be the dominant control on basement fluid composition.

Chemical composition of basement fluids within an oceanic ridge flank: Implications for along‐strike and across‐strike hydrothermal circulation

Compositions of basement fluids are presented for four sites along a 3.5‐m.y.‐ old, partly buried basement ridge on the eastern flank of the Juan de Fuca Ridge. This ridge is roughly parallel to the active ridge axis of the Endeavor Segment ∼100 km to the west. From south to north these sites are Baby Bare Outcrop, Ocean Drilling Program (ODP) Site 1026, and the southern and northern sides of Mama Bare Outcrop. The composition of basement fluids is determined or estimated from analyses of pore water samples that were extracted from sediments at each of these sites, spring waters from Baby Bare, and basement fluids that vented from the open ODP Hole 1026B. Chemical trends in basement fluids along this transect show increasing alteration from south to north. A similar trend was observed along an ODP transect perpendicular to the ridge axis with increasing fluid alteration from west to east. Much of the increase in fluid alteration along the ODP transect is explained by greater water‐rock exchange with increasing basement temperature to the east. In contrast, the trend along the 3.5‐m.y.‐old ridge is best explained by diffusive exchange with the overlying sediment. The rate of this exchange is used to constrain hydrologie properties within basaltic basement. Flow within the 3.5‐m.y.‐old ridge is inferred to occur from south to north and lacks significant exchange with basement fluids from the active ridge crest to the west. Thus the two flow systems are hydrologically distinct, and flow paths are likely influenced by the complex distribution of permeability in basement, the pattern of seafloor morphology, and the type and rate of sedimentation.

Fluid and geochemical transport through oceanic crust: a transect across the eastern flank of the Juan de Fuca Ridge

The geochemical implications of thermally driven flow of seawater through oceanic crust on the mid-ocean ridge flank have been examined on a well-studied 80 km transect across the eastern flank of the Juan de Fuca Ridge at 48–N, using porewater and basement fluid samples obtained on ODP Leg 168. Fluid flow is recognised by near-basement reversals in porewater concentration gradients from altered values in the sediment section to seawater-like values in basaltic basement. In general, the basement fluids become more geochemically evolved with distance from the ridge and broadly follow basement temperature which ranges from ~16° to 63°C. Although thermal effects of advective heat exchange are only seen within 20 km east of where basement is exposed near the ridge crest, chemical reactivity extends to all sites. Seawater passing through oceanic crust has reacted with basement rocks leading to increases in Ca 2+ and decreases in alkalinity, Mg 2+, Na +, K +, SO 2- and δ 18O. Sr isotope exchange between seawater and oceanic crust off axis is unequivocally demonstrated with endmember 87Sr/ 86Sr ~ 0.707. Evidence of more evolved fluids is seen at sites where rapid upwelling of fluids through sediments occurs. Chlorinities of the basement fluids are consistent with post-glacial seawater and thus a short residence time in the crust. Rates of lateral flow have been by estimated by modelling porewater sulphate gradients, using Cl as a glacial chronometer, and from radiocarbon dating of basal fluids. All three methods reveal fluid flow with 14C ages less than 10,000 yr and particle velocities of ~1–5 m/yr, in agreement with thermally constrained volumetric flow rates through a ~600 m thick permeable layer of ~10% porosity. Δ element/Δ heat extraction ratios are similar to values for ridge-crest hydrothermal systems.

Hydrothermal activity and the evolution of the seismic properties of upper oceanic crust

In order to investigate the impact of off‐axis hydrothermal circulation on changes of the seismic properties of upper oceanic crust (layer 2A), we performed an extensive geophysical survey on the eastern flank of the East Pacific Rise at 14°S. Seismic refraction and heat flow data were obtained along a 720‐km‐long and 25 to 40‐km wide corridor, covering thinly sedimented seafloor created since 8.5 Ma. The seismic data yield a seismic velocity of ∼2.9 km/s at the top of 0.5‐m.y.‐old basement rocks. Within about 8 m.y. the velocity increases gradually to a value of mature oceanic crust (∼4.3 km/s). Heat flow data, derived from 43 in situ thermal conductivity and 86 geothermal gradient measurements, suggest that an open hydrothermal circulation system persists for at least 6–7 m.y. In crust older than 7 Ma, regional heat flow is close to values predicted by plate cooling models, suggesting that hydrothermal circulation is going to cease. Considering published dating of alteration minerals, it appears that the permeability of uppermost oceanic crust has decreased to values insufficient to promote a vigorous hydrothermal circulation within 10–15 m.y. This idea may explain why seismic velocities in the Pacific ocean have not changed significantly in igneous crust older than 8–10 Ma. In regions where juvenile and consistently hot crust is buried rapidly by sediments the evolution of the seismic properties is quite different; velocities increase rapidly and reach values of mature oceanic crust within 1–2 m.y. We therefore favor a model where basement temperature is governing the evolution of the seismic properties of upper oceanic crust [Stephen and Harding, 1983; Rohr, 1994].

Observations concerning the vigor of hydrothermal circulation in young oceanic crust

A detailed suite of seafloor heat flow measurements and seismic reflection profiles has been completed in a young (circa 1 Ma) area on the eastern flank of the Juan de Fuca Ridge that is characterized by unusually smooth basement topography and uniform sediment cover. Measurements spaced nominally 100 m apart along one 5‐km‐long line segment define a coherent pattern of heat flow variation. The profile exhibits a series of four maxima and minima with an average half‐wavelength of 600 m and an amplitude of variation of 35 mW m−2, roughly 15% of the average background heat flow of 270 mW m−2. The heat flow variations are uncorrelated with local basement topography or sediment thickness variations and may reflect cellular convection in the extrusive layer of the igneous oceanic crust. This layer, which is bounded above by low‐permeability sediments and below by low‐permeability intrusive rocks, is imaged locally along a multichannel seismic reflection profile and estimated to be about 600 m thick. Temperatures estimated at the top of this layer by extrapolation of the seafloor heat flow measurements average roughly 40°C and vary between adjacent heat flow maxima and minima by only about 7 K. These observations, together with a series of numerical simulations of hydrothermal circulation in a confined, permeable upper crustal layer, provide quantitative insights into the convection process. Values of upper crustal permeability used in the simulations ranged from below the critical value required for convective instability to roughly 2 orders of magnitude above. Results show the amplitudes of lateral seafloor heat flow variability, upper basement temperature variability, and fluid‐pressure variability to be strongly dependent on permeability. For example, the amplitude of heat flow variations is predicted to increase rapidly above critical conditions, from zero at a subcritical permeability (k) of 2 × 10−14 m2 to 75 mW m−2 at k = 5 × 10−14 m2 and to a maximum of 90 mW m−2 at k = 8 × l0−14 m2. Predicted variability then falls roughly as k−1/2, reaching the level observed in the Juan de Fuca Ridge flank study area at a permeability of 2 × 10−12 m2. Although a value at near‐critical conditions is also allowed by the results, the higher value is probably correct, for it is known from other observations that hydrothermal circulation persists in crust of much greater age, despite the effect of chemical alteration, which reduces permeability, and thermal aging, which reduces buoyancy driving forces. The value of average permeability thus estimated for the upper oceanic crust is more than 1 order of magnitude greater than values determined in deep‐ocean boreholes. The borehole values may be lower because they are representative of older and/or more highly altered crust or because they do not correctly represent the permeability at the full scale of the convective system.

Increase of seismic velocities in upper oceanic crust and hydrothermal circulation in the Juan de Fuca plate

Two multi‐channel seismic reflection profiles have been analyzed for interval velocities and thicknesses of seismic layer 2A in crust 0–4.5 Ma created at the Endeavour segment of the Juan de Fuca plate. Stacking velocities were interpreted using the Dix assumption for interval velocity and thickness. Stacking velocities were picked from constant velocity stacks as well as normally moved‐out gathers at an interval of .2 to 2 km. Interval velocities are 3000–3500 m/s close to the ridge axis and begin to increase at 0.6 Ma when the crust is covered with a few hundred meters of Pleistocene sediments. Velocities are over 5000 m/s by 1.2 Ma, 20 km from the nearest basement outcrop. This increase is associated with an increase in basement temperature from 2–25°C to 30–50°C as heat flow values approach the predicted conductive cooling curve and the basement hydrothermal regime changes from fully open to mostly closed. Mineralisation in the abundant porosity of the upper crust is probably triggered by these thermal changes and results in increased seismic velocity. This is the first study to correlate an increase in seismic velocity with the hydrothermal regime in upper oceanic crust and demonstrates that such changes can occur in a remarkably short time.

Hydrothermal circulation through mid-ocean ridge flanks: Fluxes of heat and magnesium

Thermally driven convection of seawater occurs through oceanic crust of all ages, at the seafloor spreading axis, on mid-ocean ridge flanks, and in the ocean basins. At the ridge axis and on the flanks, circulating seawater produces a major chemical exchange between the oceans and the crust. Based on heat budget constraints and the composition of hot springs, between 10 and 40% of the river flux of Mg can be taken up during high-temperature alteration of the basaltic crust along the ridge axis. Most of the hydrothermal heat loss, however, occurs on the mid-ocean ridge flanks, where the temperatures are lower and the seawater flux correspondingly larger. The estimated heat loss on the flanks is so large that upwelling must occur over a large fraction (5–30%) of the seafloor less than 65 Ma in age, if temperatures are < 20°C and seepage velocities are on the order of 10 to 100 cm/y. The circulating seawater needs to lose on average less than 1–2% of its Mg content in order to solve the Mg mass balance for the oceans. Chemical fluxes through mid-ocean ridge flanks are poorly known because of the wide range of crustal conditions that prevail there and the paucity of study to date. The most critical parameter for characterizing crustal conditions is temperature in basement, which is a function of crustal age, basement topography, and sediment thickness and permeability. Basement temperature, which can usually be inferred from heat flow and seismic reflection surveys, largely determines the change in the composition of seawater circulating through basement. This change can be inferred, in turn, from profiles of sediment porewater chemistry. All sites studied to date with temperatures at the sediment-basement interface ≤ 25°C have a large component of advective heat loss and show only a small (< 10%) loss of Mg from the circulating seawater, whereas all sites with basement temperatures ≥ 45°C have a small advective component and show a large (> 80%) Mg loss. Both types of sites may be important for chemical fluxes. Whether the cooler sites are important depends on how much the seawater changes in composition as it circulates through the crust; only small changes are needed. Whether the warmer sites are important depends on how much heat is lost by advection in this type of setting. The warmer sites could produce significant chemical fluxes even if they are scarce: they could account for the entire river input of Mg to the oceans even if they represent only 8–20% of the total advective heat loss on ridge flanks.

Hydrothermal circulation, Juan de Fuca Ridge eastern flank: Factors controlling basement water composition

Pore water has been analyzed from sediment cores taken from three areas on the eastern flank of the Juan de Fuca Ridge as part of FlankFlux 90, a study of hydrothermal circulation through mid‐ocean ridge flanks. Seismic reflection and heat flow surveys (Davis et al., 1992a) indicate that the three areas differ in sediment thickness, basement topography, abundance of outcrops, basement temperature, and fraction of heat lost by advection versus conduction. Area 1 is on 0.6 Ma crust with nearly continuous basement outcrop, area 2 is on 1.3 Ma crust over the first buried ridge parallel to the present ridge axis, and area 3 is on 3.5–3.8 Ma crust over two axis‐parallel buried ridges that penetrate the sediment cover in three locations. Each area includes a hydrothermal system in which seawater flows into basement, reacts with crustal basalt, and then exits basement either through the sediment or directly into the overlying water column. As constrained by concentrations of sulfate and lithium in the pore waters, at least some seawater enters basement in all three areas without reacting fully with the overlying sediment, even where no outcrops are known nearby. Speeds of up welling of pore water through the sediment have been estimated by fitting profiles of dissolved magnesium and chlorinity, which behave conservatively in these areas, to numerical time‐dependent transport models. The estimated velocities range from &lt;0.1 to 7.4 cm/yr; faster flows probably occur but were not sampled. Upwelling speed correlates positively with heat flow and basement highs and negatively with sediment thickness. The correlation with heat flow differs from area 2 to area 3 along with differences in physical properties of the turbidite sediment. We have documented pore water upwelling through sediment up to 100 m thick. We estimate that upwelling continues at decreasing speeds through sediment up to 160 m thick, corresponding to a heat flow of 0.44 W/m2 in area 2 and 0.3 W/m2 in area 3. Concentrations of magnesium and chlorinity in the altered seawater upwelling from basement are uniform within each area but differ from one area to the next. Both species remain at the bottom seawater concentration in area 1, where basement is cooled to &lt;10°C at the base of the sediments mainly by advection. The concentration of magnesium decreases with increasing basement temperature in areas 2 and 3 to a minimum of 2.5 mmol/kg at about 90°C in area 3. The transition from largely advective to largely conductive heat loss occurs over only 20 km between areas 1 and 2 and corresponds to a dramatic change in the composition of fluid circulating through basement, as the uppermost basement is heated from &lt;10° to 40–50°C. Chlorinity of the basement fluid increases above the present‐day bottom seawater concentration in areas 2 and 3 and in nearly all other mid‐ocean ridge flanks studied to date, as a result of rock hydration and the higher chlorinity of bottom seawater during the last glacial period. While chlorinity generally correlates positively with uppermost basement temperature in various ridge flank hydrothermal systems, it reaches a maximum in area 2 at only 40°C, probably because alteration there occurs at a lower water/rock ratio than elsewhere. For all mid‐ocean ridge flanks studied to date, the temperature at the basement interface correlates better with the fraction of heat lost by advection versus conduction and with the average thickness of the sediment cover than with crustal age.

An electromagnetic study of Maui’s last active volcano

I have used both d.c. resistivity and time‐varying (0.2–5 Hz) magnetic field soundings to study the Ulupalakua‐Makena area on the island of Maui, the site of the last historic eruption in 1970. Using generalized inversions of the combined data, I have estimated the electrical resistivity structure beneath eight magnetometer sites. The resistivity values I obtained for electrical basement (saltwater‐saturated basalt) are reasonably consistent with a single value of 6 ± 1 Ω ⋅ m at all eight sites, although there is a suggestion of an increase in resistivity away from the coastline. The resolution matrices for the magnetic data indicated that, in addition to resolving the resistivity of electrical basement, the data were significantly affected by a combination of the resistivity of the soil layer and the depth to basement. Use of the Schlumberger data in conjunction with the magnetic data removed this correlation and resulted in good resolution for the resistivity/thickness combinations of the four upper model layers as well as for the resistivity of electrical basement. Assuming an average porosity of 20 percent for basalt and using a formation factor obtained for drillhole samples on the island of Hawaii, I estimate the basement temperature required to explain the interpreted resistivities is 59 ± 13°C. Since the penetration depth at the lowest frequency used is about 3 km, it is unlikely that these low resistivities can be explained by single flows having anomalously high porosities. I therefore conclude that the area may be of value as a low‐ to medium‐temperature geothermal resource.