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Assessment of Geothermal Resources in Petroliferous Basins in China
In order to speed up the development and utilization of hydrothermal energy, it is essential to assess the potential of geothermal resources in petroliferous basins. In this paper, the distribution of reservoirs (aquifers) and the characteristics of geothermal fields have been studied systematically based on geological, geophysical, well drilling, temperature, and sample test data obtained from the major petroliferous basins of China. It has been found that some of the porous sandstone formations in these petroliferous basins are major geothermal reservoirs and are extensively thick and widely distributed. In general, the geothermal gradient in China is higher in the eastern basins and lower in the western basins. On average, the geothermal gradient is above 30 °C/km in the Bohai Bay, Songliao, and Subei basins. The geothermal resource abundance is also higher in eastern China and in the Beibuwan basin in southern China, and the geothermal source forming condition is better, followed by the Ordos, Qaidam, and Sichuan basins in Central China. Other potential basins include the Tarim and Junggar basins in western China, where the geothermal gradient ranges between 21 and 22 °C/km, on average. In this paper, three methods, stochastic simulation, unit volumetric, and analogy, were used for the assessment of geothermal resources. Using the stochastic simulation and unit volumetric methods, the geothermal resources, annual recovered geothermal resources, geothermal water resources, and thermal energy of water in 11 basins or blocks of up to 4000 m deep were calculated. Grading evaluation criteria were established by considering the heterogeneity of geothermal reservoirs. The results showed that the petroliferous basins are very rich in geothermal resources. The annual recoverable resources reach 1626.8 × 106 tons of standard coal, in which grade I, grade II, and grade III resources are 641.9 × 106, 298.6 × 106, and 686.3 × 106 tons of standard coal, respectively. The results demonstrate that the development and utilization of geothermal energy in oilfields has a huge potential for industrial production and family use, and a great significance for the development of green oilfields. With the high demand of heat, the eastern oilfields with high geothermal resource abundance should be the first to be considered for the production and utilization of geothermal energy, followed by the central and western oilfields.
Journal Article
Multidecadal declines in particulate mercury and sediment export from Russian rivers in the pan-Arctic basin
High levels of methylmercury accumulation in marine biota are a concern throughout the Arctic, where coastal ocean ecosystems received large riverine inputs of mercury (Hg) (40 Mg·y−1) and sediment (20 Tg·y−1) during the last decade, primarily from major Russian rivers. Hg concentrations in fish harvested from these rivers have declined since the late 20th century, but no temporal data on riverine Hg, which is often strongly associated with suspended sediments, were previously available. Here, we investigate temporal trends in Russian river particulate Hg (PHg) and total suspended solids (TSS) to better understand recent changes in the Arctic Hg cycle and its potential future trajectories. We used 1,300 measurements of Hg in TSS together with discharge observations made by Russian hydrochemistry and hydrology monitoring programs to examine changes in PHg and TSS concentrations and fluxes in eight major Russian rivers between ca. 1975 and 2010. Due to decreases in both PHg concentrations (micrograms per gram) and TSS loads, annual PHg export declined from 47 to 7 Mg·y−1 overall and up to 92% for individual rivers. Modeling of atmospheric Hg deposition together with published inventories on reservoir establishment and industrial Hg release point to decreased pollution and sedimentation within reservoirs as predominant drivers of declining PHg export. We estimate that Russian rivers were the primary source of Hg to the Arctic Ocean in the mid to late 20th century.
Journal Article
Craton deformation from flat-slab subduction and rollback
The mechanisms underlying the deformation and eventual destruction of Earth’s cratons remain enigmatic, despite proposed links to subduction and deep mantle plume processes. Here we study the deformation of the North China Craton using four-dimensional mantle flow models of the plate–mantle system since the late Mesozoic, integrating constraints from lithospheric deformation, mantle seismic tomography and the evolution of surface topography. We find that flat-slab subduction induced landward shortening and lithospheric thickening, while subsequent flat-slab rollback caused seaward extension and lithospheric thinning. Both subduction phases resulted in substantial topographic changes in basin sediments. Rapid flat-slab rollback, coupled with a viscosity jump and phase change across the 660 km mantle discontinuity, was a key ingredient in shaping a large mantle wedge. We argue that craton deformation through lithospheric extension and thinning was triggered by the subduction of a flat slab and its subsequent rollback. The integration of data into mechanical models provides insights into the four-dimensional dynamic interplay involving subduction, mantle processes, craton deformation and topography.
Mesozoic deformation of the North China Craton occurred via lithospheric thickening followed by thinning and extension triggered by flat-slab subduction and rollback, according to four-dimensional mantle flow models of the plate–mantle system.
Journal Article
Rivers across the Siberian Arctic unearth the patterns of carbon release from thawing permafrost
Climate warming is expected to mobilize northern permafrost and peat organic carbon (PP-C), yet magnitudes and system specifics of even current releases are poorly constrained. While part of the PP-C will degrade at point of thaw to CO₂ and CH₄ to directly amplify global warming, another part will enter the fluvial network, potentially providing a window to observe large-scale PP-C remobilization patterns. Here, we employ a decade-long, high-temporal resolution record of 14C in dissolved and particulate organic carbon (DOC and POC, respectively) to deconvolute PP-C release in the large drainage basins of rivers across Siberia: Ob, Yenisey, Lena, and Kolyma. The 14C-constrained estimate of export specifically from PP-C corresponds to only 17 ± 8% of total fluvial organic carbon and serves as a benchmark for monitoring changes to fluvial PP-C remobilization in a warming Arctic. Whereas DOC was dominated by recent organic carbon and poorly traced PP-C (12 ± 8%), POC carried a much stronger signature of PP-C (63 ± 10%) and represents the best window to detect spatial and temporal dynamics of PP-C release. Distinct seasonal patterns suggest that while DOC primarily stems from gradual leaching of surface soils, POC reflects abrupt collapse of deeper deposits. Higher dissolved PP-C export by Ob and Yenisey aligns with discontinuous permafrost that facilitates leaching, whereas higher particulate PP-C export by Lena and Kolyma likely echoes the thermokarst-induced collapse of Pleistocene deposits. Quantitative 14C-based fingerprinting of fluvial organic carbon thus provides an opportunity to elucidate large-scale dynamics of PP-C remobilization in response to Arctic warming.
Journal Article
Timing of the initiation and duration of the Cretaceous extensional regime in South‐east China: Constraints from growth strata in terrigenous basins
There has been no consensus yet regarding the precise initial timing and duration of the late Mesozoic extensional tectonics in the South‐eastern China Block. This work focusses on the growth strata of the Early Cretaceous red beds in the South‐eastern China Block to determine the late Mesozoic tectonics and the precise timing of the initiation and duration of extensional tectonics in this area. Field observation of several terrigenous basins shows that the dip angles of the Cretaceous red beds have varied from moderate to gentle from basin edges to interiors (or centres). The visible and estimated thickness within a single bed increases slightly downwards from the upper to the lower part. These characteristics indicate that the sedimentary area of these beds has undergone an extensional process with expansion and deepening of the sedimentary basins. Rotation of the border surfaces (limbs) and downward warping of the hanging walls or retreat of the footwalls of listric normal faults causes three types of extensional growth (or syntectonic) strata in the deposits of different basins. Dating of the volcanic rocks related to the growth beds reveals that the sedimentary basins were enlarged and deepened when the Early Cretaceous strata were deposited in the South‐eastern China Block from ca 140 to 137 Ma. Regionally, under the influence of Palaeo‐Pacific plate rollback since ca 140 Ma, the South‐eastern China Block stress field has led to lithospheric uplift and pull‐apart structures near the surface, causing the half‐graben basins to receive sedimentation. Although the extensional event was interrupted by a short compressional event during 120 to 105 Ma, with the oceanward retreat of the trench, the area of extension gradually enlarged and rejuvenated south‐eastwards until the end of the Cretaceous. This Cretaceous extension event of the South‐eastern China Block must belong to a worldwide geological event with global significance.
In the Cretaceous half‐graben basins of south‐east China, the variation of dip angles and thickness of red beds shapes four types of extensional growth strata. The rollback of the Palaeo‐Pacific plate results in the half‐graben and the NW‐SE extensional stress field which begins at ca 140 to 137 Ma in the South‐eastern China Block and lasts until the end of the Cretaceous, except for a compressional stage from 120 to 105 Ma.
Journal Article
The ecology of the Barí : rainforest horticulturalists of South America
No detailed description available for \"The Ecology of the Barí\".
eBook
The Miocene Western Balkan lithium-boron metallogenic zone
The Western Balkan lithium-boron metallogenic zone can be traced for 1500 km, extending subparallel to the Sava-Vardar and Western Vardar zones toward its Turkish counterpart, the Izmir-Ankara-Erzincan zone. Common features are: (1) lithium-boron mineralization is hosted in Lower-Middle Miocene extensional lacustrine basins; (2) lacustrine series consisting of fine-grained siliciclastic sediments and scarce evaporites with intercalations of volcaniclastics, tuff, or travertine indicating syndepositional volcanic activity; (3) lacustrine basins that are usually normal-fault-controlled extensional grabens, with the fault system probably acting as a major fluid pathway; (4) northernmost sodium borate/borosilicate deposits (Jadar, Valjevo, Rekovac; with jadarite, borax, probertite, searlesite) gradually transition to calcium borate deposits southward (Jarandol-Piskanja, Pobrđe; with colemanite ± ulexite); (5) Oligocene/Miocene granitic rocks from the westernmost part of the zone host pegmatite and greisen occurrences with surface lithium anomalies of 0.02–0.08 wt% Li2O extending for several km2; (6) igneous Li enrichment by fractionation processes is indicated for some younger (?Early/mid-Miocene) peraluminous granite plutons; (7) the formation of the lacustrine basins and associated Li-B mineralization was contemporaneous with the emplacement of the younger phase of Li-bearing granitic intrusions and exhumation of metamorphic core complexes which provided the large-scale heat flow for hydrothermal systems and syngenetic Li-B mineralization.
Journal Article