Injection Of Hydrothermal Fluids Research Articles

Temporal constraints on hydrothermal circulation associated with strike-slip faulting in the Permian Maokou carbonates, central Sichuan Basin (SW China)

Despite the ubiquity of hydrothermal fluid circulation in the crust, its timing is difficult to precisely determine using traditional thermometric dating due to strongly disturbed geothermal fields. We present a case study from the mid-Permian hydrocarbon-bearing dolostone reservoirs, situated proximally to strike-slip faults in the central Sichuan Basin (China), to highlight the utility of carbonate in-situ U-Pb geochronology in delineating the timing of hydrothermal fluid flow. Matrix and void-filling cement dolomite phases were identified in the porous Maokou Formation carbonates. Predominantly manifesting as saddle dolomites along fractures, these cements yielded statistically homogeneous U-Pb ages (242.5 ± 3.1 Ma, 238.9 ± 8.2 Ma, 244 ± 15 Ma, and 239.2 ± 6.5 Ma), slightly postdating the established stratigraphic timeline (ca. 273 to 259 Ma). The narrow temporal span suggests early emplacement following a short burial, compatible with the petrographic observation of burial stylolites crosscutting saddle dolomites. Integrating shallow emplacement depths inferred from a comparison between the dolomite U-Pb ages and a published burial history, with fluid-inclusion microthermometry, elucidates the hydrothermal system that was once present in this field. The pervasive occurrence of hydrofracturing, along with dolomite geochemical indicators represented by bell-shaped (REE + Y) PAAS patterns and elevated Y/Ho ratios, provide additional evidence for the hydrothermal fluid injection and resulting dolomitization. The dolomites' positive Eu anomalies and the parent fluids’ 18O enrichment indicate a source from deeper basinal pore waters that have interacted significantly with ambient rocks. The overlying Triassic evaporites may have provided Mg-rich brines, mixing into the circulating hot fluids responsible for hydrothermal dolomitization. Our dolomite U-Pb ages coincide with the seismically estimated timing of transtensional strike-slip fault activation. This temporal correspondence, combined with spatial associations and lateral slickensides along fracture planes, suggests that the hydrothermal fluid movement is highly relevant to the active strike-slip faults. This observation reveals a previously unrecognized early-middle Triassic, structurally controlled hydrothermal activity in the region. We propose that this episode of hydrothermal circulation was driven by extensional tectonism in response to the spreading of the Proto-Tethys Ocean. This finding is not in line with the earlier research that considered late Permian Emeishan volcanism to have been the main trigger for hydrothermal fluid influx. The long-standing view regarding hydrothermal dolomitization in this region may need to be re-evaluated.

Mineralogy and geochemistry of the Late Triassic coal from the Caotang mine, northeastern Sichuan Basin, China, with emphasis on the enrichment of the critical element lithium

Comprehensive research on the concentrations, modes of occurrence, and origin of critical elements in coal is significant from an economic point of view. Several previous investigations have attributed the host of critical elements such as Li, Ga, Nb, Ta, Zr, and Hf in coals to aluminosilicate minerals derived from terrigenous input, while Li of hydrothermal origin has rarely been found in coals. The Late Triassic coal of the Caotang mine, northeastern Sichuan Basin, China of this study is a high-ash, medium-sulfur, low volatile bituminous coal. The dominant minerals in these coals are illite, calcite, kaolinite, and quartz, with minor chlorite, sulfate minerals, paragonite, pyrite, and anatase, along with traces of phosphate minerals. In comparison with the world hard coals and Chinese common coals, the critical element Li is ∼20-times higher in the Caotang coal. The Li concentrations (range 89.1–520 μg/g, 291 μg/g on average) and the abundance of chlorites in coal low-temperature ashes (LTAs) show a strong correlation (r = 0.88), indicating that chlorites are the dominant host of Li in the coal. The chlorite minerals in this study belong to three types: cookeite, chamosite, and a chlorite mineral of intermediate composition between them. Both the kaolinite-cookeite assemblage with a vermicular texture and Li-bearing chlorite occurring as fracture-fills, indicate that they formed by interaction of kaolinite with Li-rich solutions or directly precipitated from Li-bearing solutions during diagenetic or epigenetic processes. Based on geochemical indicators such as Al2O3/TiO2 ratios, rare earth elements and yttrium (REY) distribution patterns, and the relationship between Al2O3/TiO2 and Zr/TiO2 and Nb/Yb ratios, the source-area compositions of Caotang coals are felsic-intermediate igneous rocks from the southeast Qinling thrust system, Longmenshan thrust belt, Hannan Upland, and Micangshan-Dabashan Uplift. The kaolinite-paragonite assemblage with authigenic minerals such as chamosite, anatase, calcite, barite, pyrite, quartz, and REY-rich minerals, as well as the REY enrichment patterns, suggest that the Caotang coals may have been subjected to a multi-stage injection of hydrothermal fluids. The Caotang coal is considered to be a promising source of the critical element Li. Furthermore, the concentrations of the critical elements Ga, Nb, and Ta in the coal increase its potential economic significance even further.

Locating hydrothermal fluid injection of the 2018 phreatic eruption at Kusatsu-Shirane volcano with volcanic tremor amplitude

Kusatsu-Shirane volcano hosts numerous thermal springs, fumaroles, and the crater lake of Yugama. Hence, it has been a particular study field for hydrothermal systems and phreatic eruptions. On 23 January 2018, a phreatic eruption occurred at the Motoshirane cone of Kusatsu-Shirane, where no considerable volcanic activity had been reported in observational and historical records. To understand the eruption process of this unique event, we analyzed seismic, tilt, and infrasound records. The onset of surface activity accompanied by infrasound signal was preceded by volcanic tremor and inflation of the volcano for ~ 2 min. Tremor signals with a frequency band of 5–20 Hz remarkably coincide with the rapid inflation. We apply an amplitude source location method to seismic signals in the 5–20 Hz band to estimate tremor source locations. Our analysis locates tremor sources at 1 km north of Motoshirane and at a depth of 0.5–1 km from the surface. Inferred source locations correspond to a conductive layer of impermeable cap-rock estimated by magnetotelluric investigations. An upper portion of the seismogenic region suggests hydrothermal activity hosted beneath the cap-rock. Examined seismic signals in the 5–20 Hz band are typically excited by volcano-tectonic events with faulting mechanism. Based on the above characteristics and background, we interpret that excitation of examined volcanic tremor reflects small shear fractures induced by sudden hydrothermal fluid injection to the cap-rock layer. The horizontal distance of 1 km between inferred tremor sources and Motoshirane implies lateral migration of the hydrothermal fluid, although direct evidence is not available. Kusatsu-Shirane has exhibited unrest at the Yugama lake since 2014. However, the inferred tremor source locations do not overlap active seismicity beneath Yugama. Therefore, our result suggests that the 2018 eruption was triggered by hydrothermal fluid injection through a different pathway from that has driven unrest activities at Yugama.

Resources of critical metals in coal-bearing sequences in China: Enrichment types and distribution

Coal is a particular sedimentary organic ore and has a huge resource worldwide. Coal is a resource primarily used for electric power generation, and currently supplies 41% of global electricity needs. Significant quantities of coal are also employed in metallurgical processes, gasification, cement industries, and as raw materials for activated carbon and many common and industrial chemicals, as well as for heat for the wallboard, aluminum, and cement industries. A number of coals can also be considered as an economic source of some critical metals, and thus are coal-hosted ore deposits. The critical metals in coal and coal-bearing sequences occur at concentrations comparable to or even higher than those in conventional economic deposits. China is, and in the coming decades should continue to be, the largest producer and user of coal in the world. The high volume of coal usage in China has led to attention not only on the toxic elements that may be released from coal combustion but also on the critical metals that may occur in the coal and coal-bearing sequences, as well as coal combustion by-products. Critical elements (e.g., Ge, Ga, U, rare earth elements and Y, Nb, Zr, Se, V, Re, Au, and Ag, as well as the base metal Al) in a number of coals (or coal ashes) and some coal-bearing strata in China occur at concentrations comparable to or even higher than those in conventional economic deposits. This paper reviewed the distribution and ore-forming mechanism of some typical coal-hosted ore deposits in China, including Ge, Ga-Al, rare earth elements (REE), and Nb-Zr-REE-Ga. Additionally, other critical metals such as Be, Sc, Li, Mg, V, and Re in coal and coal bearing sequences have also been briefly reviewed. Several geological factors are responsible for the deposition of coal-hosted critical metals, including injection of hydrothermal fluids during peat accumulation or later epigenetic stages, deposition of syngenetic alkali volcanic ashes in peat swamp, input of terrigenous mineral matter into the coal-forming environment, leaching of partings by groundwater, and mixed processes involving both hydrothermal solutions and volcanic ash. Mixed processes involving both hydrothermal solutions and volcanic ash are also important geological factors that contribute to the deposition of coal-hosted critical metals. The critical metals in Chinese coal and coal-bearing sequences may be associated with either the organic matter or minerals. For example, germanium exclusively occurs in the organic matter; gallium mainly occurs in boehmite and kaolinite, and to a lesser extent, in the organic matter; rare earth elements and Y occur as carbonate minerals (e.g., florencite and parisite), phosphate minerals (e.g., rhabdophane, silico-rhabdophane, and xenotime), and in part are associated with the organic matter. Some critical metals (e.g., Ge, Al, and Ga) have been successfully extracted at an industrial scale from Chinese coals, and others have significant potential for such extraction. Major challenges remaining for coal scientists include the development of economic extraction methods from coal ash, and the control of toxic elements released during the metal extraction process to protect human health and to avoid environmental pollution.

Mineralogy and Geochemistry of the No. 5−2 High-Sulfur Coal from the Dongpo Mine, Weibei Coalfield, Shaanxi, North China, with Emphasis on Anomalies of Gallium and Lithium

This paper reports the mineral compositions and geochemical characteristics of the No. 5−2 high-sulfur coal (Taiyuan Formation) from Dongpo Mine, Weibei Coalfield, Shaanxi, Northern China via transmitted and reflected light microscopy, scanning electron microscope equipped with an energy-dispersive X-ray spectrometer (SEM-EDS), X-ray diffraction (XRD), inductively coupled plasma mass spectrometry (ICP-MS), and X-ray fluorescence spectrometry (XRF). We also confirmed the input of intermediate-felsic volcanic ashes into the Taiyuan Formation coals in Dongpo Mine, Weibei Coalfield. The results show that Dongpo coals are enriched in Ga and Li compared to the average values for world hard coals, and they are depleted in Al2O3 compared to Chinese coals. The coal low temperature ash contains kaolinite, illite, quartz, calcite, pyrite, and to a lesser extent, chlorite, plagioclase, dolomite, ankerite, and apatite. The concentration anomalies of Ga and Li in No. 5−2 high-sulfur coal were not caused by the Benxi Formation Bauxite, but by the influence of multiple geological factors. The Middle Proterozoic moyite from the Yinshan Oldland led to the slightly higher Ga and Li contents of the No. 5−2 coal than those in world hard coals. Input of synchronization volcanic ash, injection of hydrothermal fluids during the syngenetic or early diagenetic stages and influence of seawater further contributed to the Ga and Li enrichment of the No. 5−2 coal.

Characteristics of hydrothermal-structure-controlled fracture-vug dolomite reservoir and its influence on oil-water distribution: Lower Cretaceous, Baiyinchagan sag, Erlian Basin, North China

Fractures and vugs were used as the primary dolomite reservoir space in the study area, which improved the reservoir’s physical properties and influenced the distribution pattern of oil and water that were developed in the Upper Tenger Formation, Lower Cretaceous, Baiyinchagan sag, Erlian Basin. Based on the core observation data, thin slice analysis, and image logging, the cave-fractured reservoir was primarily developed in the actic region near the side of a depositional fault. Tectonic and diagenetic fractures were the primary types of fractures. High-angle tectonic fractures in the closure and open status were developed well in dolomitic mudstone, while a low-angle fracture and reticulate fractures were developed in the tectonic-hydrothermal hybrid process and were filled with hydrothermal minerals. The reservoir was located in low-lying land; therefore, detrital grain pressolution fractures were formed by burial diagenesis. Intergranular and intrangranular dissolved pores, which were formed by hydrothermal activity, were developed primarily in the highly dolomite lithology. According to the diagenesis temperature of dolomite from a carbon-oxygen isotope analysis, multiple hydrothermal fluid injection events occurred, and dolomitization ensued before massive hydrocarbon migration. The dissolution of organic acids formed by hydrocarbon charges after dolomitization and inorganic acid produced by burial di agenesis for soluble minerals effectively promoted the reservoir properties. Strong heterogeneity due to lithology and fracture-vug systems led to intricate oil-water relationships. Four statuses occurred, including cave-fracture oil, isolated oil, stored oil, isolated water, and stored water. The oil-water distribution patterns were established based on the core observation.

Pseudotachylyte and Fluid Alteration at Seismogenic Depths (Glacier Lakes and Granite Pass Faults, Central Sierra Nevada, USA)

We present evidence for ancient seismicity in the form of tectonic pseudotachylyte and coeval, cyclic hydrothermal alteration, and cataclasis along fault zones exhumed from 2.4 to 6.0 km in the central Sierra Nevada, CA. The Glacier Lakes fault (GLF) and Granite Pass fault (GPF) are exhumed left-lateral to left-lateral oblique, strike-slip faults with up to 125 m of left-lateral separation exposed in Mesozoic granite and granodiorite plutons. Precipitation of epidote along fault slip-surfaces, chloritization of biotite, saussurite and sericite alteration of plagioclase, and quartz- and-calcite filled veins are present in the GLF and GPF zones. One difficulty encountered in studying exhumed fault zones is providing convincing evidence for a frictional melt origin of pseudotachylyte. Rocks in the field may preserve convincing evidence for frictional melt (i.e., aphanitic, dark, injection structures) that are later shown to be related to cataclasis or injection of hydrothermal fluids. Another challenge results from the low preservation potential of several of the microscopic features that are convincing evidence of a frictional melt origin (microlites, amygdules, and glassy matrix). Here we test the usefulness of grain shape and nearest neighbor distribution analysis of pseudotachylyte and cataclasites from the GLF and GPF to discriminate between these fault rocks and to determine a frictional melt origin for pseudotachylyte. Fabric analyses of the clasts within the pseudotachylytes examined are more circular and exhibit a random nearest neighbor clast distribution relative to adjacent cataclasites. With increased comminution and melting the mean clast circularity increases and the nearest neighbor distances approach a random distribution. We conclude that this observed pattern can be applied to other fault zones as an indicator of a frictional melt origin for fault-related rocks. Mutually cross-cutting zones of hydrothermal alteration and calcite deformation twins constrain the ambient temperature conditions in the fault zone to between 170 and 320 °C during pseudotachylyte formation. Based on previous thermochronologic studies, the temperature conditions of the country rock during faulting were between 110 and 220 °C. The overlapping to elevated temperatures in the fault zone can be explained by: (1) infiltration of hydrothermal fluids into the fault zone; or (2) residual elevated temperatures as a result of frictional heating in the fault zone during seismic slip.

Pre-eruptive ground deformation of Azerbaijan mud volcanoes detected through satellite radar interferometry (DInSAR)

Mud volcanism is a process that leads to the extrusion of subsurface mud, fragments of country rocks, saline waters and gases. This mechanism is typically linked to hydrocarbon traps, and the extrusion of this material builds up a variety of conical edifices with a similar morphology to those of magmatic volcanoes, though smaller in size. The Differential Interferometry Synthetic Aperture Radar (DInSAR) technique has been used to investigate the ground deformation related to the activity of the mud volcanoes of Azerbaijan. The analysis of a set of wrapped and unwrapped interferograms, selected according to their coherence, allowed the detection of significant superficial deformation related to the activity of four mud volcanoes. The ground displacement patterns observed during the period spanning from October 2003 to November 2005 are dominated by uplift, which reach a cumulative value of up to 20 and 10cm at the Ayaz–Akhtarma and Khara-Zira Island mud volcanoes, respectively. However, some sectors of the mud volcano edifices are affected by subsidence, which might correspond to deflation zones that coexist with the inflation zones characterized by the dominant uplift. Important deformation events, caused by fluid pressure and volume variations, have been observed both (1) in connection with main eruptive events in the form of pre-eruptive uplift, and (2) in the form of short-lived deformation pulses that interrupt a period of quiescence. Both deformation patterns show important similarities to those identified in some magmatic systems. The pre-eruptive uplift has been observed in many magmatic volcanoes as a consequence of magma intrusion or hydrothermal fluid injection. Moreover, discrete short-duration pulses of deformation are also experienced by magmatic volcanoes and are repeated over time as multiple inflation and deflation events.

Repeated injection of hydrothermal fluids into downdip carbonates: a diagenetic and stratigraphic mechanism for localization of reservoir porosity, Indian Basin Field, New Mexico, USA

Abstract A detailed study of the Pennsylvanian Indian Basin Field of New Mexico, USA is used to develop a conceptual model that predicts reservoir porosity in clean down-depositional-dip marine carbonate, where repeated fracturing allows for hydrothermal fluid flow. Strata updip probably experienced repeated events of subaerial exposure, resulting in mineralogical stabilization and extensive calcite cementation that prevented extensive hydrothermal alteration. Clean, carbonate sediment deposited downdip was more prone to alteration by hydrothermal fluids. In the reservoir, cement stratigraphy shows regionally persistent zones closely associated with fracturing. Fluid inclusion data show high temperatures and repeated rises and falls, indicating tectonic valving in a hydrothermal system. Salinity data support this and indicate a late event of meteoric influx. Sr- and O-isotope data indicate higher temperature and less rock–water interaction in fault damage zones, evidence for intensified fluid flow in such areas. Formation of vugs and molds was associated with the hydrothermal fluid flow, which was driven by convection, probably initiated during 40–30 Ma intrusive activity and continuing after the onset of Basin and Range uplift and unroofing.

Numerical models of caldera deformation: Effects of multiphase and multicomponent hydrothermal fluid flow

Ground surface displacement (GSD) in large calderas is often interpreted as resulting from magma intrusion at depth. Recent advances in geodetic measurements of GSD, notably interferometric synthetic aperture radar, reveal complex and multifaceted deformation patterns that often require complex source models to explain the observed GSD. Although hydrothermal fluids have been discussed as a possible deformation agent, very few quantitative studies addressing the effects of multiphase flow on crustal mechanics have been attempted. Recent increases in the power and availability of computing resources allow robust quantitative assessment of the complex time‐variant thermal interplay between aqueous fluid flow and crustal deformation. We carry out numerical simulations of multiphase (liquid‐gas), multicomponent (H2O–CO2) hydrothermal fluid flow and poroelastic deformation using a range of realistic physical parameters and processes. Hydrothermal fluid injection, circulation, and gas formation can generate complex, temporally and spatially varying patterns of GSD, with deformation rates, magnitudes, and geometries (including subsidence) similar to those observed in several large calderas. The potential for both rapid and gradual deformation resulting from magma‐derived fluids suggests that hydrothermal fluid circulation may help explain deformation episodes at calderas that have not culminated in magmatic eruption.

THERMAL RESERVOIR MODEL ANALYSIS OF THE YANGBAJING GEOTHERMAL FIELD,XIZANG (TIBET) AUTONOMOUS REGION

Based on the analyses of temperature field in subsurface geothermal reservoir aud un-derlying granitic batholith of the Yangbajing Geothermal Field, both the difference in res-servoir eharacters of the northern and southern parts of the field and their identity in heatervoir characters of the northern and southehave been ascertained. Furthermore, it hasbeen establishedt hat the Nyainqentanglha and Tanggulashan piedmont fault zones are thecontrolling structures for the boundary of the geothermal field; meanwhile, the distributionof lithological character of the Quaternary system in the reservoir is the main controllingfactor for the geothermal reservoir behaviours. In accordance with the temperature datafrom the deep drill holes in the geothernml field, a heat transfer model down to a depth of3.3 km in basement rocks has been worked out. Using the principles of transient heat trans-fer and heat balance a rough estimate has been obtained that the last hydrothermal fluidinjection into the geothermal reservoir occurred about tens of thousands years B. P., i.e. asurface manifestation of the latest deep thermal activity of the Qinghai-Xizang (Tibet) Pla-teau under recent tectonic stress.

Water column anomalies associated with hydrothermal activity in the Guaymas Basin, Gulf of California

Sea floor hydrothermal activity in the Guaymas Basin, Gulf of California, is quite different from that associated with ridge crest spreading centers. Injection of hydrothermal fluids occurs in the bottom of a semi-enclosed basin and water column anomalies produced by this activity increase to much higher values than in the open ocean. In the Guaymas Basin the hydrothermal venting generates large clouds of fine suspended particulate matter (SPM) 100–300 m above active mounds and chimneys. These hydrothermal clouds have potential temperature anomalies of about 0.010–0.020°C, are enriched in dissolved silica, particulate manganese, and depleted in dissolved oxygen relative to areas away from the vents. The particulate manganese values increase from about 3 nmol/kg at ∼ 1000 m, well above the enclosing topography of the subsill basin, to 100–150 nmol/kg in the clouds of SPM and in the bottom nepheloid layer. The particulate Mn in the hydrothermal clouds appears to originate from both direct precipitation of dissolved Mn 2+ injected by the vents and entrainment of Mn-rich SPM in the rising hydrothermal plumes. Injection of silica-rich vent fluids into the basin bottom waters produces a silica anomaly of 10–15 μmol relative to the other deep basins of the Gulf of California. Spillover of Guaymas Basin deep water produces a silica plume just above the basin sill depth which is detectable to the mouth of the Gulf. A simple two-endmember mixing model indicates that the deep waters of the Guaymas Basin contain approximately 0.1% hydrothermal fluid. Oxygen anomalies associated with the hydrothermal clouds are on the order of 5 μmol relative to regions away from active vents. The basin as a whole shows a depletion in oxygen of about 13 μmol relative to the other deep basins of the Gulf. The mixing model shows that this oxygen consumption can be explained by the oxidation of dissolved sulfide and methane injected by the hydrothermal vents. Box models of the deep basins of the southern Gulf of California indicate that the Guaymas Basin has a significantly higher source term for dissolved silica and sink term for dissolved oxygen than the other basins. The calculated flux of hydrothermal fluids into the Guaymas Basin is 10–12 m 3/s.