Curie Isothermal Surface Research Articles

Geothermal structure revealed by curie isothermal surface under Guangdong Province, China

Guangdong Province in Southeast China is noted for its numerous geothermal resources due to tectonic episodes, mainly occurred during the Cretaceous. The surface heat flow and geothermal gradient are the most direct ways to understand the temperature of the Earth. However, geothermal resources are poorly utilized in Guangdong Province due to limited numbers of boreholes and surficial hydrothermal fluids. To improve the understanding of underground temperature distribution in Guangdong Province, we have applied power-density spectral analysis to aeromagnetic anomaly data to calculate the depth of the Curie isothermal surface. Upward continuation is applied and tested to the magnetic data. The calculated Curie isotherm is between 18.5 km and 25 km below surface. The fluctuation in the depth range reflects lateral thermal perturbations in the Guangdong crust. In particular, the eastern, northern, western and coastline areas of the province have a relatively shallow Curie isotherm. By comparing the surface heat flow, geothermal gradient, distribution of Mesozoic granite-volcanic rocks, and natural hot springs, we conclude that during Mesozoic, magmatism exerted great influence on the deep thermal state of Guangdong Province. A shallow Curie isotherm surface, as well as numerous natural hot springs and high heat flow, show clear signatures of shallow heat sources.

Crustal structure of Sicily from modelling of gravity and magnetic anomalies

We aim at modeling the main crustal and thermal interfaces of Sicily (Italy), a key area for understanding the geological complexity at the collisional boundary between the African and European plates. To this end, we analyze the gravity and magnetic fields, integrated with information from well logs, geology, heat flow, and seismic data. In order to make the most accurate description of the crustal structure of the area, we modeled with different methodologies the carbonate and crystalline top surfaces, as well as the Moho and the Curie isotherm surface. The reconstruction of the carbonate platform is achieved using a nonlinear 3D method constrained by the available seismic and borehole data. The crystalline top, the Curie, and the Moho are instead estimated by spectral analysis of both gravity and magnetic data. The results show a complex carbonate basement and a deep crystalline crust in central Sicily, with a prominent uplift beneath the Hyblean Plateau. Maps of the Moho and the Curie isotherm surface define a variable thermal and structural setting of Sicily, with very thin crust in the southern and eastern sectors, where high heat flow is found, and deep and cold crust below the Caltanissetta Basin.

Determination of Curie Depth Isotherm and Geothermal Studies over Parts of Nasarawa and Environs, North Central Nigeria

The high resolution aeromagnetic data was analyzed to estimate depths to the bottom of magnetic sources as proxy information about the thermal conditions within the crust in Nasarawa area. This area is particularly important for geothermal exploration because of its high heat flow and geothermal gradients. The result of this investigation revealed that Curie point depth vary between 18km and 23km with deeper Isotherm at the northwestern part and shallow Isotherm at the south eastern part, this means that the Curie Isotherm surface around Awe Dorowa and Akiri may likely coincide with the Moho, these variations of curie depth isotherm could be related to the different tectonic activities, which involve astenospheric updoming, crustal thinning and stretching, emplacement of igneous bodies and block faulting in the Benue Trough. The calculated heat flow varies between 63 mWm^-2- 80 mWm^-2 and geothermal gradient varies between 25°C/km- 32°C/km. The south eastern part is characterized by high heat flow (80mW/m²), and shallow Curie depth (18 km), due to the geothermic nature of the area, the heat due to magmatic activities as well as heat from thinning of the crust is responsible for raising the temperature in these areas. The north western portion of the studied area has lower heat flow (63mW/m²) and deeper Curie depth (23 km) due to Isostacy. Variations in the Curie Depth compare reasonably well with the heat flow and with the Geothermal Gradient, this study also revealed that the south eastern part of the study area has potentials for geothermal energy.

Relationship between Curie isotherm surface and Moho discontinuity in the Arabian shield, Saudi Arabia

The Arabian shield is a Precambrian complex of igneous and metamorphic rocks located approximately one-third of the way across the western Arabian Peninsula, with uncommon exposures along the Red Sea coast. We used aeromagnetic data acquired by others over the past several decades to estimate the depth to the Curie temperature isotherm throughout this region. Our goal was to further understand the lithospheric structure, thermal activity, and seismicity to assist in geothermal exploration. We also compared the Curie temperature isotherm with the crustal thickness to investigate the possibility that mantle rocks are magnetic in some parts of the Arabian shield.Depths to the Curie isotherm were estimated by dividing the regional aeromagnetic grid into 26 overlapping windows. Each window was then used to estimate the shape of the power spectrum. The windows had dimensions of 250×250km to allow investigation of depths as deep as 50km. The results show the presence of a Curie isotherm at a depth of 10–20km near the Red Sea, increasing to 35–45km in the interior of the Arabian shield. The Curie isotherm generally lies above the Moho in this region but deepens into the mantle in some locations, notably beneath the Asir Terrane.

Interpretations of gravity and magnetic anomalies in the Songliao Basin with Wavelet Multi-scale Decomposition

In this paper, we introduce the method of Wavelet Multi-scale Decomposition (WMD) combined with Power Spectrum Analysis (PSA) for the separation of regional gravity and magnetic anomalies. The Songliao Basin is situated between the Siberian Plate and the North China Plate, and its main structural trend of gravity and magnetic anomaly fields is NNE. The study area shows a significant feature of deep collage-type construction. According to the feature of gravity field, the region was divided into five sub-regions. The gravity and magnetic fields of the Songliao Basin were separated using WMD with a 4th order separation. The apparent depth of anomalies in each order was determined by Logarithmic PSA. Then, the shallow high-frequency anomalies were removed and the 2nd-4th order wavelet detail anomalies were used to study the basin's major faults. Twenty-six faults within the basement were recognized. The 4th order wavelet approximate anomalies were used for the inver- sion of the Moho discontinuity and the Curie isothermal surface.

Distribution of the crustal magnetic anomaly and geological structure in Xinjiang, China

Based on the high-order crustal magnetic field model NGDC-720-V3, we investigate the distribution of crustal magnetic anomaly, the decay characteristics of the anomaly, and the relationship between the magnetic anomaly and geological structure in Xinjiang, China. Topography of the magnetic layer basement is studied through Curie isothermal surface using the power spectrum method. It is found that south Tarim Basin, Junggar Basin, and Turpan–Hami Basin have strong positive magnetic anomaly, whereas west Kunlun Mountain, Altun Mountain, Tianshan Mountain, and Altai Mountain have weak or negative anomaly. The magnetic anomaly well reflects the regional tectonic structure, i.e., three alternating mountains intervened by two basins. The magnetic anomaly on the ground surface in Tarim Basin is well corresponding to the mafic dykes. The decay of the magnetic anomaly with altitude indicates that Xinjiang is a large massif composed of several magnetic blocks with different sizes in different directions. The Curie surface presents a feature of being shallow under mountains whereas being deep under basins, roughly having an anti-mirror correspondence with the Moho depth.

Distribution of Magnetic Anomalies in China and Adjacent Areas Derived from CHAMP Satellite Data

AbstractBased on the new and higher degree geomagnetic model POMME‐4.2S from CHAMP satellite data, we have calculated satellite magnetic anomalies and their vertical gradients at altitude 400 km in China and adjacent areas. The distributions of seven magnetic components are shown. In addition, we also compared the impact of the truncation level on the magnetic anomalies and analyzed the relationship between the anomalies and the lithospheric structure. The results indicate that the ∆X(∆Y) magnetic anomaly foci appear on the south (west) and north (east) sides of that of ∆Zin the main magnetic anomaly areas of the Sichuan, Tarim and Songliao basins. The configuration of the magnetic anomaly distribution is determined when the spherical harmonic model is up to 90 degrees, and only a minor modification to the magnetic anomaly is required for higher degrees. The anomaly and its vertical gradient are varying synchronously in the strong magnetic anomaly areas. The satellite magnetic anomaly has no direct corresponding relations with the topographic change, distribution of faults, depth of the Moho and the thickness of the lithosphere. However, this anomaly is connected with the depth of the Curie isotherm interface and the thickness of the magnetic layer, which is positive (negative) in the areas of deeper (shallower) Curie isotherm surface and thicker (thinner) magnetic layer.

Epeirogeny in the Southern Rocky Mountains region: Evidence and origin

The mountain peaks of the present-day Southern Rocky Mountains are the highest peaks in the Rocky Mountain system. They represent a second generation of mountains, one that originated from a different tectonic mechanism from that of the predecessor Laramide Rockies. Epeirogeny lifted the Laramide ranges in Colorado and New Mexico after their Late Cretaceous–early Cenozoic orogenic creation. The area was lifted tectonically from 1300 m to perhaps as much as 2000 m, the result of heating of the lithosphere stemming from its thinning, as well as inflation of the crust by the intrusion of extensive, relatively low density batholiths and plutons of middle Tertiary age. This uplift produced an elongate north-striking crustal swell that cuts across major structural features in the crust, including the northeast-trending fundamental sutures that resulted from assembly of the North American plate, the northwest-striking trends of the Ancestral Rocky Mountains in Colorado, and the northeast-trending Colorado Mineral Belt. The contemporary Southern Rockies are unique in that their eastern piedmont slope is quite unlike that of other prominent orogenic mountain ranges around the globe owing to the presence of this supporting swell, or epeirogen. The lithosphere beneath the epeirogen9s summit is characterized by a coincident geoid anomaly, diminished seismic velocities in the upper mantle, and a north-trending, elevated Curie isothermal surface in the lower crust, all suggestive of elevated temperatures. Surface heat flow on the summit is complex, revealing both shallow crustal heat sources and a much deeper, more profound source that strikes north. Uplift resulting from these factors was initiated in post–middle Eocene time. At the wavelength of topographic smoothing employed here, the epeirogen9s regional topography makes it the highest general feature on the North American plate, individual mountain peak elevations, here and elsewhere, excepted. A first-order, re-leveled survey line in southern Colorado suggests that the epeirogen is still rising today.

Study of Curie isothermal surface in Sichuan Basin and the seismic area on its western margin

Using the aeromagnetic data and the method of 3—D magnetic stratum inversion, the data of aeromagnetic anomalies in the investigated region have been processed; and thereby the quantitative buried depth of the Curie isothermal surface in Sichuan Basin and its western marginal area has been obtained. The reliability of the inversion results has been confirmed by the features of regional tectonics, the distribution of geothermal gradient and the results of deep seismic sounding. By analyzing the deep geothermal field, it is concluded that the followings are the environmental conditions for the development and occurrence of earthquakes in the western marginal area of Sichuan Basin: (1) The collision of the Yangtze block with the Sichuan-Qinghai block and Kangdian rhombic block has produced strong stress accumulation; and (2) Plastic creep in the middle-lower crust owing to the up-welling of mantle flux has provided an adjusting unit for rock rupture and stress release.

Research on geomagnetic tectonic characteristics of the crust in Haicheng seismic area

In this paper, the two metnods, rectangular spectrum (RS) and maximum entropy power spectrum (MES), have been used in calculating the geomagnetic structures of the crust in Haicheng and its adjacent areas and carrying out the geomagnetic stratification of the crust. The result of the research indicates that the crust can be devided into such three layers as nonmagnetic layer, magnetic layer and regressive magnetic layer from the top to the bottom. It is also found the distribution of the geomagnetic bottom interface (Curie surface) is consistent with the lower interface of the upper crust and the top interface of the middle crust of the velocity structure of the crust. It is very interesting that the Haicheng earthquake of Feb. 4, 1975,M 7.3 occurred at the depth gradient belt of the Curie isotherm surface. So, to research on the geomagnetic layers and the distribution characteristics of the Curie isotherm surface is meaningful in judging potential seismic foci.

Gravity and magnetic investigations of the Sierra Nevada batholith, California

Research Article| March 01, 1977 Gravity and magnetic investigations of the Sierra Nevada batholith, California HOWARD W. OLIVER HOWARD W. OLIVER 1U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar Author and Article Information HOWARD W. OLIVER 1U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1977) 88 (3): 445–461. https://doi.org/10.1130/0016-7606(1977)88<445:GAMIOT>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation HOWARD W. OLIVER; Gravity and magnetic investigations of the Sierra Nevada batholith, California. GSA Bulletin 1977;; 88 (3): 445–461. doi: https://doi.org/10.1130/0016-7606(1977)88<445:GAMIOT>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Gravity data are now available for about 90 percent of the Sierra Nevada batholith, magnetic data for about 30 percent. About 1,000 density and 250 magnetic property measurements have been made on selected samples. Bouguer gravity anomalies decrease about 200 mgal, from −40 to −240 mgal, eastward across the batholith and gradually rise about 50 mgal on its east side. Gravity calculations show that these Bouguer anomalies are consistent with the general form of Bateman and Eaton's seismic model of the central Sierra Nevada and are inconsistent with the model of Carder and others. The calculations confirm Eaton's velocity-density relation for crystalline rocks. The major gravity step across the western Sierra Nevada is caused primarily by a mafic mountain root, not the batholith. Local anomalies of −5 to −40 mgal are associated with the most leucocratic felsic plutons. Correlation with available isotope ages shows the gravity anomalies to be largest and broadest over the youngest Cretaceous plutons, which suggests that they extend to greater depths than the older, exposed plutons.Magnetic contrasts between plutons are generally much greater than density contrasts, and they provide a method for mapping some of the more magnetic plutons under some types of cover. The depth extent of magnetic plutons in Yosemite National Park is at least 7 km and probably greater. A regional magnetic low centered near the western edge of the Sierra Nevada correlates with a regional depression in the Curie isothermal surface, as evidenced by low surface heat flux. Because the depression in the isotherm allows for a greater thickness of material to be magnetic, the magnetic low is unexpected, and the relation is a noteworthy paradox.Bouguer gravity anomalies correlate fairly well with initial Sr87/Sr86 ratios, and the magnetic field correlates with oxidation ratios of sampled granitic rocks. These data, together with physical property measurements of gneissic and peridotitic xenoliths discovered in volcanic pipes by J. P. Lockwood, form a foundation on which new models of the petrogenesis and structure of the batholith must be based. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

The Blue Road Geotraverse: A magnetic ground survey and the interpretation of magnetic anomalies

Abstract Ground measurements of the magnetic field were carried out along a 20-km-wide zone along the Blue Road Geotraverse. In addition, a profile of high precision was measured. A large positive anomaly within the mountain area cannot be explained by anomalous magnetization of surface rocks. Optimization of theoretical models shows that it may have its origin at a depth of 30 km, indicating a rise of the Curie isothermal surface from the mountain area to the Baltic shield. The rise of the isotherm may be connected with the land uplift. Interpretation of smaller anomalies reveals the thickness of sedimentary layers.

New recognition of NNE-strike belt of negative aeromagnetic anomaly in Tibetan plateau

DOI = 10.3126/hjs.v5i7.1310 Himalayan Journal of Sciences Vol.5(7) (Special Issue) 2008 p.123-124