The majority of Earth’s basaltic volcanism occurs at mid-ocean ridges, where new ocean floor is created. Especially young oceanic crust, which is highly porous and permeable, is subject to regional off-axis hydrothermal circulation, which extracts large amounts of heat and impacts global water and chemical fluxes between the ocean and the lithosphere. Generally, seawater recharge and hydrothermal fluid discharge happen where the basaltic crust is exposed to the seafloor. This mode of circulation is usually referred to as outcrop-to-outcrop flow. Basaltic aquifers, overlain by impermeable sedimentary layers, can sustain outcrop-to-outcrop flow over distances of several 10s of kilometers. Basaltic rock formations are also explored for their potential to store injected CO2 with the added benefit that carbonation reactions promote the safe long-term storage. In this context, it is uncertain whether natural hydrothermal flow between outcropping seamounts compromises a long-term storage or whether it will help to continuously expose injected CO2 to fresh reactive basaltic rock.Numerical fluid flow modelling on different scales is a powerful tool to understand the relations between off-axis hydrothermal circulation and CO2 storage. On the one hand, coupled heat transfer and fluid flow modelling of regional ridge flank flow can be performed at the kilometer scale and compared with heat flow observations. By using such regional models, we find that outcrop-to-outcrop flow arises if the permeability of the basaltic aquifer is larger 10-13 m2. This regional crustal permeability primarily controls the flow velocity and discharge mass fluxes. In the presence of outcrop-to-outcrop flow, the permeability and geometric shape of the outcrops further determine the direction of the flow. Secondly, the flow rates and fluid temperatures in the aquifer are influenced by the thickness of the sediment and the distance between the outcrops, respectively. These results based on regional models help to constrain flow patterns through the basaltic crust from seafloor observations, e. g. heat flow measurements in the sediment. Understanding these regional flow patterns is a compelling necessity in the context of CO2 sequestration on mid-ocean ridge flanks.On the other hand, in-situ carbon mineralization in porous basaltic crust can modify crustal permeabilities on local and regional scales, and thus influence regional circulation patterns. In this regard, we use pore scale numerical fluid flow simulations based on core samples in combination with laboratory experiments to parameterize the permeability evolution during carbonization reactions. Results of pore-scale modelling can be incorporated into the regional flow models to further enhance understanding of the interplay between off-axis hydrothermal circulation and carbon sequestration in mid-ocean ridge basalts.

Deep-sea mining magnifies the release of heavy metals into seawater through oxidative dissolution of seafloor massive sulfide (SMS). At present, there is little information about how the metals released into seawater might be affected by the mineral assemblages, seawater conditions, and solid percentages. Here, leaching experiments were carried out to examine the behavior of three sulfides from the Southwest Indian Ridge, under conditions that replicated deep and shallow seawater environments at three solid-liquid ratios. The results demonstrated that sphalerite dissolved rapidly, and the metals released in both experimental conditions were comparable, potentially reflecting galvanic interactions between the sulfide minerals. Large quantities of the released metals were removed from the solutions when hydrous ferric oxides formed, especially for shallow seawater conditions. A comparison of metal concentrations in the leachates with the baseline metal concentrations in natural seawater indicated that most of the released metals, when diluted with seawater, would not have widespread impacts on ecosystems. Based on the obtained unique oxidative dissolution properties of each SMS at variable solid-liquid ratios, targeted wastewater discharge treatments are proposed to minimize impacts from the dissolved metals. This study will support the development of robust guidelines for deep-sea mining activities.

Plate tectonics describes oceanic transform faults as conservative strike-slip boundaries, where lithosphere is neither created nor destroyed. Seafloor accreted close to ridge-transform intersections (RTI) has therefore been expected to follow a similar subsidence trend with age as lithosphere that forms away from RTIs. Our recent combined analysis of high-resolution bathymetric data, satellite gravity, and three-dimensional numerical models from transform faults segmenting mid-ocean ridges across the entire spectrum of spreading rates challenges this concept. One striking observation is that transform faults are systematically deeper than their adjacent fracture zones. Gravity data suggests that the underlying reason may be changes in crustal thickness, with transform valleys having thin and fracture zones ‘normal’ crustal thicknesses. Another observation is that outside corner crust often shows symmetric abyssal hills with intact flat top volcanoes, while the inside corner regions show intense and oblique tectonic deformation. Furthermore, so-called J-shaped ridges, volcanic ridges that bend towards the active transform, show that magmatic accretion occurs predominantly along the spreading axis, ‘feeling’ the rotating stress field only in the direct vicinity of the RTI. While these observations do show some dependence on spreading rate, they can be identified across a wide range of opening rates, suggesting that they are expressions of processes inherent to transform faulting.In this contribution, we will review these observations before presenting numerical 3-D thermo-tectono-magmatic models designed to elucidate the underlying processes. These models use a dilation term to mimic magmatic accretion and resolve visco-elasto-plastic deformation. The simulations show that the tectonic deformation axis, the axis of plate separation, becomes oblique at depth resulting in extension and crustal thinning within the transform deformation zones. Complementing simulations that account for magmatic accretion and hydrothermal cooling show that a skew can develop between this oblique deformation axis and the axis of magmatic accretion, implying a possible disconnect between the main diking direction and the direction of tectonic deformation. Taken all evidence together, oceanic transform faulting appears to be much more complex than pure strike-slip motion. It shows a surprisingly complex pattern of tectonic faulting and hints at spill-over magmatism at the RTI. Crustal accretion at ridge transform intersections may therefore be fundamentally different to accretions elsewhere along mid-ocean ridges.

The significant discrepancy between the observed conductive heat flow and predictions by thermal models for oceanic lithosphere younger than 50 Ma is generally interpreted to result from hydrothermal circulation between basement outcrops. Numerical simulations of fluid flow between such outcrops performed in previous studies revealed that establishing horizontal pressure gradients to sustain a hydrothermal siphon requires high aquifer permeabilities and a contrast in the outcrops’ transmittance, which is the product of the outcrop permeability and the area of outcrop exposure. However, most previous studies focused on the model parameters needed to sustain a hydrothermal siphon, while the physical processes that create the horizontal pressure gradients in the first place remain poorly constrained. In order to shed more light on the physics behind outcrop-to-outcrop flow, a simple synthetic 2D model of two outcrops connected by a permeable aquifer was set up. Fluid flow modelling was done by using hydrothermalFoam, a hydrothermal transport model, that is based on the open-source C++ computational fluid dynamics toolbox OpenFOAM. Our initial simulations focus on variations of the permeability of the outcrops and the aquifer. The results reveal two key points that are essential to generate a flow: First, the outcrops permeability has a fundamental effect on its average pressure. High permeabilities lead to a rather "cold" hydrostatic pressure regime with lower temperatures and hence higher average pressures. Lower outcrop permeabilities are accompanied with a rather "warm" hydrostatic pressure regime characterized by higher temperatures and lower average pressures. Secondly, fluid convection in the aquifer is necessary to establish a siphon flow. Therefore, the aquifer permeability must be sufficiently high to overcome Darcy resistance and yet low enough to prevent the flow from being solely diffusive.

<p>Gravity signals over the mid-ocean ridge-transform system reflect the distribution of underlying crustal and upper mantle mass anomalies. The gravity measurement, especially ‘residual’ gravity anomalies, relies on the gravitational corrections of both seafloor relief and lithospheric thermal structure. Lithospheric thermal correction typically uses a 1D plate cooling approximation or a 3D passive flow model that assumes isoviscous mantle rheology. As this rheological approximation is oversimplified and physically complex, how sensitive gravity anomalies are to an increasingly complex/accurate approximation for mantle rheology is still unresolved. Here we systematically examine the residual gravity anomaly discrepancies caused by assumptions of different mantle rheologies on 16 natural ridge-transform systems ranging from ultraslow- to fast-spreading. Our calculations show that estimated residual gravity anomalies are significantly lower (e.g., ~21 mGal lower at mid-ocean ridges) in the isoviscous flow models than in the static plate cooling models, primarily due to the effects of lateral heat advection and conduction. When the assumed mantle rheology is changed from uniform viscosity to a non-Newtonian viscosity with brittle weakening in cooler (faulting) regions, the mantle upwelling intensifies and local near-surface temperature generally increases, resulting in an increase in the residual anomaly. This increase is distributed uniformly along the ultraslow-and slow-spreading ridge axes, but is concentrated along transform faults at intermediate- and fast-spreading ridges. The amount of the rheology-induced gravity difference is most closely linked to transform age offset instead of spreading rate or transform offset length alone. Our analysis reveals that oceanic transform faults exhibit higher gravity anomalies than adjacent fracture zones, which may reflect thinner crust in the transform deformation zone.</p>

Submarine massive sulfide deposits on slow-spreading ridges are larger and longer-lived than deposits at fast-spreading ridges, likely due to more pronounced tectonic faulting creating stable preferential fluid pathways. The TAG hydrothermal mound at 26∘N on the Mid-Atlantic Ridge (MAR) is a typical example located on the hanging wall of a detachment fault. It has formed through distinct phases of high-temperature fluid discharge lasting 10s to 100s of years throughout at least the last 50,000 yrs and is one of the largest sulfide accumulations on the MAR. Yet, the mechanisms that control the episodic behavior, keep the fluid pathways intact, and sustain the observed high heat fluxes of possibly up to 1700 MW remain poorly understood. Previous concepts involved long-distance channelized high-temperature fluid upflow along the detachment but that circulation mode is thermodynamically unfavorable and incompatible with TAG's high discharge fluxes. Here, based on the joint interpretation of hydrothermal flow observations and 3-D flow modeling, we show that the TAG system can be explained by episodic magmatic intrusions into the footwall of a highly permeable detachment surface. These intrusions drive episodes of hydrothermal activity with vertical discharge and recharge along the detachment. The numerical simulations reveal that the high-temperature circulation system at TAG may be confined to a vertical zone of enhanced permeability that channelizes upflow and a recharge system that is hosted by the detachment surface with a high permeability of 2×10−13 to 10−12m2. This revised flow regime reconciles problematic aspects of previously inferred circulation patterns and allows to identify the prerequisites for generating substantive seafloor mineral systems.

Marine gravity data can provide information on the distribution of mass anomalies in the oceanic crust and upper mantle. Computing corresponding gravity anomalies, especially so-called 'residual' gravity anomalies that directly reflect variations in the crustal structure, relies on gravity corrections of both seafloor relief and lithospheric thermal structure. The lithospheric thermal gravity correction involves either a plate cooling approximation or a mantle flow model with the latter typically done using simplified assumptions on mantle rheology. However, a detailed study of how differing rheological models affect the computed gravity anomalies is still missing. Here, we systematically examine the differences in residual mantle Bouguer anomalies (RMBA) caused by differing assumptions on mantle rheology for 16 mid-ocean ridge - transform fault systems. Our calculations show that isoviscous models tend to underpredict RMBA values within the transform deformation zone and overpredict them in the far field at older plate ages, when compared to plate cooling and nonlinear viscoplastic models. This discrepancy stems from isoviscous models failing to capture plate-like deformation, as well as their inability to resolve brittle failure and the associated strain localization that leads to warm upwelling beneath the transform fault. By exploring a wide parameter range, we find that the importance of mantle rheology scales with plate tectonic parameters at the mid-ocean ridge - transform fault system such as transform age offset, spreading rate, and transform fault length. These findings suggest that gravity thermal corrections at the intrinsically threedimensional ridge - transform systems should employ mantle flow models that resolve plate-like deformation and brittle failure.

Hydrothermal activity in the mid-ocean ridge facilitates the chemical exchange of seawater with new oceanic crusts. This activity mostly occurs on the detachment fault of the asymmetric accretion segment in the slow-ultraslow spreading ridge, which is characterised by limited magma supply. Deep faults can readily extract heat from deeper heat sources. Moreover, the repeated movement of faults activates the permeable fluid channels of the overlying oceanic crust, thus driving long-life hydrothermal circulation. Recent studies have found that the response time of the hydrothermal activity of the intermediate-fast spreading ridges differs from that of the slow-spreading ridge to the glacial cycle, and a unified model is expected to explain it. Also, the response of hydrothermal activity to the glacial cycle must consider the differences between oceanic ridges with different spreading rates and types of hydrothermal systems.Here, based on two sediment cores collected near the Yuhuang hydrothermal field (HF)on ultraslow-spreading Southwest Indian ridge, we obtained high-resolution sediment history records spanning three glacial periods, understood the 160 ka history of hydrothermal, volcanic and tectonic activities in the region and attempted to reveal the response mechanism of hydrothermal activities controlled by detachment faults to the glacial cycle. We discovered that in the Yuhuang HF controlled by detachment faults, hydrothermal activity increased significantly during the glacial period, and more active detachment fault activity appeared at the same time. At the end of the glacial period, both activities are reduced at the same time. We believe that in the slow-ultraslow spreading ridge, the magmatism regulated by sea level changes may regulate the evolution of detachment faults and the hydrothermal circulation, which are recorded in the sediments near the hydrothermal field.We established a response model of Sea level change–Magmatism–Detachment fault activity–Hydrothermal activity and concluded that the magmatism of slow-ultraslow spreading ridges is more sensitive to sea level changes; with the synchronous effect of detachment faults, the hydrothermal activity responds faster to the glacial cycle.

Polymetallic sulfides present in mid-ocean ridges (MORs) have become important strategic resources for humans, and a scientific metallogenic model is necessary for the investigation and exploration of these resources. Compared to fast- and slow-spreading MORs, ultraslow-spreading MORs show substantial differences in magma supply, tectonic activity, and oceanic crust structures. However, information on hydrothermal circulation and a metallogenic model related to sulfides along the ultraslow-spreading ridges is still limited, which hinders further exploration of these resources. In this study, the distribution of hydrothermal activities, as well as the characteristics of the structures, heat sources, fluid pathways, host rock types, fluid properties, and sulfide assemblages in typical hydrothermal fields along the ultraslow-spreading Southwest Indian Ridge (SWIR), have been studied. It is concluded that the hydrothermal systems along the SWIR can be categorized into three types, including local enhanced magma-controlled, one-way detachment/high-angle large-offset fault-controlled, and flip-flop detachment-controlled types, which are further categorized into five subtypes based on their distinct geological backgrounds. Herein, we present a sulfide metallogenic model called Local Enhanced Heat Supply-Deep Faults (eHeat-dFault) for the SWIR. The overall spreading rate remains almost constant (14–18 mm/year), while the magma supply is heterogeneous in the segment scale along the SWIR. Over the past two decades, various hydrothermal systems and sulfide deposits have been identified along the SWIR. A deep magma chamber (4–9 km) is developed in the ridge segment with sufficient magma supply owing to the local enhanced magma supply, while long-lived active deep detachment faults (up to 13 km) with associated metallogenic belts are developed in ridge segments with poor magma supply. Hence, the ultraslow-spreading MORs fulfill the necessary conditions of a sustained heat source and stable hydrothermal pathway for the formation of large-scale polymetallic sulfide deposits. The number of hydrothermal fields detected in the investigation area is 2–3 times that predicted by the traditional Spreading Rate-Magma Flux model, demonstrating its significant endowment for sulfide resources. A balance between magma supply and faulting may influence the type and depth of hydrothermal circulation, the frequency of hydrothermal activity along the axis, and the scale of sulfide deposits. Spreading rate was previously believed to control heat sources, magma supply, and tectonic processes. However, for the SWIR, we suggest that local enhanced heat supply and deep detachment faults have a greater influence than the spreading rate on hydrothermal circulation and sulfide mineralization. The eHeat-dFault sulfide metallogenic model proposed herein could provide guidance for further exploration and research on polymetallic sulfides in ultraslow-spreading SWIR.

Details on the geodynamic model, thermal correction, and additional results of all 11 transform faults.

Plate tectonics describes oceanic transform faults as conservative strike-slip bound-aries, where lithosphere is neither created nor destroyed. Therefore, seafloor accreted at ridge-transform intersections should follow a similar subsidence trend with age as lithosphere that forms away from ridge-transform intersections. Yet, recent compila-tions of high-resolution bathymetry show that the seafloor is significantly deeper along transform faults than at the adjacent fracture zones. We present residual mantle Bouguer anomalies, a proxy for crustal thickness, for 11 transform fault systems across the full range of spreading rates. Our results indicate that the crust is thinner in the transform deformation zone than in either the adjacent fracture zones or the inside corner regions. Consequently, oceanic transform faulting appears not only to thin the transform valley crust but also leads to a secondary phase of magmatic addition at the transition to the passive fracture zones. These observations challenge the concept of transform faults being conservative plate boundaries.

洋中脊多金属硫化物已经成为人类重要的战略资源,科学的成矿模型是对其调查研究和勘探的重要依据.相较快速、慢速扩张洋中脊,超慢速扩张洋中脊在岩浆供给、构造和围岩等特征均存在明显差异,但目前对其热液循环及硫化物成矿模型缺乏系统梳理,制约了其资源勘探评价与研究的有效进程.本文系统总结了超慢速扩张西南印度洋中脊热液活动分布以及典型热液区的构造、热源、热液通道、围岩类型、流体性质和硫化物等特征,根据其成矿地质背景的差异性特点将该洋中脊赋存的热液系统分为局部强岩浆控制型、单向拆离/高角度大偏移距断层控制型以及双向拆离控制型三类,根据岩浆供给率（M值）的大小进一步将其划分为五种类型,从而建立了超慢速扩张西南印度洋中脊的局部强热供给-深大断裂控制硫化物成矿模型.超慢速扩张西南印度洋中脊扩张速率整体变化不大（14～18mm/a）,岩浆供给呈分段不均匀性.通过近20年的调查研究,发现其发育类型多样的热液系统和硫化物.在岩浆供给充足的洋脊段,发育局部强岩浆供给条件下的深部岩浆房（4～9km）.而在岩浆供给贫瘠的洋脊段,发育长期持续活动的深大拆离断层（可达13km）,并沿拆离断层形成成矿带.因而超慢速扩张洋脊具备形成大型多金属硫化物矿床所需的持续热源和稳定热液通道的必要条件.已调查区探测到的热液活动区数量是传统扩张速率-岩浆通量模型预测的2～3倍,具有良好的硫化物资源前景.洋中脊热液循环系统的类型、循环深度、热液活动沿轴发育频率以及硫化物成矿规模可能是岩浆供给和构造活动均衡贡献的结果.通常认为扩张速率控制着热源、岩浆供给和构造过程.对于超慢速扩张西南印度洋中脊,本文认为局部强热供给和深大断裂构造是其热液循环和硫化物成矿更直接的控制因素.局部强热供给-深大断裂控制的硫化物成矿模型有望为超慢速扩张西南印度洋中脊多金属硫化物的勘探与成矿研究提供指示.

Hydrothermal systems are integral to mid-ocean ridge activity; they form massive seafloor sulfide (SMS) deposits rich in various metallic elements, which are potential mineral resources. Since 2007, many hydrothermal fields have been discovered along the ultraslow-spreading Southwest Indian Ridge (SWIR). The Duanqiao hydrothermal field is located at segment 27's axis between the Indomed and Gallieni transform faults; tomography models reveal an obvious low-velocity anomaly beneath it, indicating a possible axial magma chamber (AMC). However, confirmation of an AMC's existence requires further study and evidence. In this study, we first calculated the gravity effect to identify the heterogeneous distribution of crustal density beneath segment 27 and the surrounding area. Next, we used the gravity-inversion method to obtain the crustal density structure beneath the study area. The results indicate that a thickened crust and low-density crustal materials exist beneath segment 27. The low-density anomaly in the lower crust beneath the Duanqiao hydrothermal field suggests the existence of an AMC covered with a cold and dense upper crust. The density results identify several faults, which provide potential channels for magma migration. In addition, the melt migrates westward and redistributes laterally toward the segment's western end. However, when migrating toward the segment's eastern end, the melt is affected by a rapid cooling mechanism. Therefore, the segment's ends present different density features and morphologies of nontransform discontinuities (NTDs).

AbstractChanges in sea level caused by glacial cycles may influence the magmatism and hydrothermal activity of oceanic ridges. Recent studies showed that the response time of the hydrothermal activity in the intermediate-fast spreading ridges differs from that in the slow-spreading ridges to the glacial cycles, and a unified model is expected to explain it. Here, we report the 160 ka sediment record adjacent to the Yuhuang hydrothermal field on the Southwest Indian Ridge. Hydrothermal and detachment fault activities were found to enhance or weaken during glacial and interglacial periods, respectively. The magmatism of slow/ultraslow spreading ridges is more sensitive to sea level changes; with the synchronous effect of detachment faults, the hydrothermal activity responds faster to the glacial cycles. We established a model of Sea level change–Magmatism–Detachment fault activity–Hydrothermal activity to explain the different responses of the hydrothermal activity of the mid-ocean ridges to the glacial cycles.

为了探索高渗透性洋壳中高温热液循环系统的形成机制,以数值模拟为手段研究热液循环中的矿物沉淀过程及其对洋壳渗透率的反馈.在热液对流-矿物反应模型中考虑了硬石膏、黄铁矿和黄铜矿的沉淀和溶解反应,基于矿物的溶度积计算矿物的沉淀/溶解量,并将其转换为渗透率的变化.结果显示,黄铁矿和黄铜矿分布于350～380°C等温线范围内,并随着热液温度升高而逐渐向海底推移.海水被加热及与热液混合过程中沉淀出硬石膏,在热液上升通道两侧形成低渗透性的烟囱状结构,降低了海水-热液混合程度从而使热液温度升高.高温热液通道建立后,便会有更多的金属物质随着高温热液被运输至浅层洋壳或海底.模拟结果为理解海底高温热液喷口的形成机制提供了借鉴.

The stable downward continuation is an important and difficult problem in magnetic data processing and interpretation. The downward continuation of the magnetic field is an unstable process, wherein high-frequency signals will be rapidly amplified and overwhelm useful signals. Although the suppression of high-frequency signals can allow for the acquisition of smooth downward continuation results, this will lead to a loss of amplitude in the data. Therefore, it remains challenging to reproduce the amplitude and shape of a magnetic anomaly well synchronously. Based on the good performance of the dual-layer equivalent source method when processing magnetic data, a stable and high precision downward continuation approach is proposed. The synthetic data tests show that the proposed approach can obtain results with a high accuracy. Notably, this new technique provides a stable scheme for the downward continuation of the magnetic anomaly field. Application of the approach to aeromagnetic data helps to verify the stability of the proposed method.

High‐temperature hydrothermal venting has been discovered on all modern mid‐ocean ridges at all spreading rates. Although significant strides have been made in understanding the underlying processes that shape such systems, several first‐order discrepancies between model predictions and observations remain. One key paradox is that numerical experiments consistently show entrainment of cold ambient seawater in shallow high permeability ocean crust causing a temperature drop that is difficult to reconcile with high vent temperatures. We investigate this conundrum using a thermo‐hydro‐chemical model that couples hydrothermal fluid flow with anhydrite‐ and pyrite‐forming reactions in the shallow subseafloor. The models show that precipitation of anhydrite in warming seawater and in cooling hydrothermal fluids during mixing results in the formation of a chimney‐like subseafloor structure around the upwelling, high‐temperature plume. The establishment of such anhydrite‐sealed zones reduces mixing between the hydrothermal fluid and seawater and results in an increase in vent temperature. Pyrite subsequently precipitates close to the seafloor within the anhydrite chimney. Although anhydrite thus formed may be dissolved when colder seawater circulates through the crust away from the spreading axis, the inside pyrite walls would be preserved as veins in present‐day metal deposits, thereby preserving the history of hydrothermal circulation through shallow oceanic crust.

Coupled magmatic and tectonic activity plays an important role in high-temperature hydrothermal circulation at mid-ocean ridges. The circulation patterns for such systems have been elucidated by microearthquakes and geochemical data over a broad spectrum of spreading rates, but such data have not been generally available for ultra-slow spreading ridges. Here we report new geophysical and fluid geochemical data for high-temperature active hydrothermal venting at Dragon Horn area (49.7°E) on the Southwest Indian Ridge. Twin detachment faults penetrating to the depth of 13 ± 2 km below the seafloor were identified based on the microearthquakes. The geochemical composition of the hydrothermal fluids suggests a long reaction path involving both mafic and ultramafic lithologies. Combined with numerical simulations, our results demonstrate that these hydrothermal fluids could circulate ~ 6 km deeper than the Moho boundary and to much greater depths than those at Trans-Atlantic Geotraverse and Logachev-1 hydrothermal fields on the Mid-Atlantic Ridge.

We have discovered a number of technical issues in the original version of Hydrother-malFoam v1.0.0.For the convenience of the reviewers and early users of Hydrother-malFoam, we have fixed those issues and document the changes in this "short comment".In particular, we have fixed a few issues in the benchmark and cookbook cases, both in the docker container and in the gitlab source directory, and have have updated the thermoPhysical model.

As a significant data processing method, the potential field continuation is usually implemented in frequency domain, but rarely in spatial domain. However, the space-domain method has the advantages of being more accurate and flexible. In this study, we propose a new numerical integral approach to solve the integration equation. The algorithm can be applied to upward continuation as well as stable downward continuation, and can be used to obtain continued potential field data from a plane upward to a surface and from a surface downward to a plane. A smooth fitting curve is proposed to determine optimal iterative number for the iteration procedure of the algorithm. Both synthetic and field data are used to test the proposed approach and compare with previous studies. The numerical experiment results indicate the proposed method has a stable numerical performance and a wide range of application.