Meso‐Cenozoic thermal structure of the lithosphere in the Bohai Bay Basin,eastern North China Craton

Thermal structure of the lithosphere studies the partition of crustal and mantle heat flow of the continental area and is of significant importance to understand various energy‐related geodynamic processes. The study addresses the spatial distribution of the Meso‐Cenozoic mantle heat flow and Moho temperatures in the region of the Bohai Bay Basin based on the thermal history of the sedimentary basin, radioactive heat production rate and thickness of crustal layering. The results show that the ratio of the mantle and surface heat flow (q_m/q_s) experienced two peaks in the late period of the Early Cretaceous (q_m/q_s ~ 68%) and the Middle to Late Palaeogene (q_m/q_s ~ 75%), respectively. Based on the q_m/q_s ratio, the lithosphere of the Bohai Bay Basin transformed its thermal structure during the Meso‐Cenozoic, from the ‘cold mantle but hot crust’ stage in the Triassic–Jurassic to the ‘hot mantle but cold crust’ stage in the Cretaceous and Cenozoic. The Moho temperatures (T_m) during the Meso‐Cenozoic were also calculated by using the equation of one‐dimensional heat conduction, and the result shows that there exist three T_m peaks occurring in the late period of the Early Cretaceous (930–1080 °C), the Middle‐Late Palaeogene (820–890 °C) and the Early Neogene (770–810 °C). The q_m/q_s ratio began to exceed 50%, and the Moho temperature started to go over 700 °C from the Cretaceous to the present day, which revealed that the activity of the upper mantle in the eastern North China Craton (NCC) increased significantly accompanied by the strong crustal movement in the Cretaceous. The thermal structure revealed the Cretaceous to be a revolutionary period during the evolution of the Bohai Bay Basin, and this paper may provide some thermal evidence for the studies of the geodynamic evolution during the destruction of the NCC. Copyright © 2015 John Wiley & Sons, Ltd.     

东亚西太平洋岩石圈三维结构及其地幔动力学

欧亚大陆及其边缘海地区是由约30多块尺度不同、形成时代和性质各异的板块或地块拼合而成。这些岩石圈板块或地块经过长时间的漂移,多次聚合与分离,碰撞与增生,在新生代最后形成现代的拼合欧亚大陆。欧亚大陆及其边缘海的板块或地块可以分为以下六类:(1)前寒武纪巨型克拉通地块及地盾;(2)前寒武纪小型克拉通地块及板块;(3)显生宙造山带及汇聚地块;(4)陆陆碰撞型地块及造山带;(5)新生代边缘海海盆;(6)大陆裂谷盆地及增生地块。高分辨率地震面波层析成像,显示同一类型的板块或地块的岩石圈和软流圈的速度结构十分相似,呈现出其独有的速度分布特征。不同类型板块或地块的速度结构有重大差异。直到400km深度,各个板块和地块的横向差异才逐渐减小。一般而言,前寒武纪克拉通板块及地块的岩石圈巨厚具有高速性质、软流圈很薄或不存在;边缘海、造山带等区域岩石圈较薄和速度较低,软流圈发育。根据欧亚大陆及边缘海地区天然地震层析成像,人工地震剖面数据及其他有关资料,建立了欧亚大陆及其边缘海岩石圈模型。     

中国大陆大规模成矿作用油气田形成——来自岩石圈的约束

由克拉通、造山带、裂谷、边缘海洋壳和岛弧等5大岩石圈类型构成的中国大陆,由于不同类型岩石圈对应的动力学机制及其效应不同,岩石圈不同类型之间的连接带必定是不连续带,与大陆成矿作用有密切的联系。中国大陆已知的绝大多数金属矿床分布于岩石圈不连续和再活化不连续处,表明岩石圈不连续为大型矿床(矿集区)形成提供有利的运-储空间。中国大陆西北、中国东部和西南地区构造-岩浆-成矿事件序列对比表明,一个地区岩石圈的壳-幔岩石学结构、大规模成矿作用,取决于最强的、最后一次的岩浆作用,大规模成矿作用的发生起始于造山岩石圈根失稳、去根和大规模软流圈上涌时期,C型埃达克岩的出现是其标志之一。分布于中国内陆的扬子、鄂尔多斯、塔里木和准噶尔盆地等地表热流值低的“冷盆”,深部属于克拉通型岩石圈背景,在构造上往往为造山带的前陆盆地,克拉通型岩石圈构造上的稳定性决定了这些克拉通盆地不断被周围造山带吞食、掩埋、改造的格局,虽然在这些盆地内如今都已发现油气田,但在盆地外那些现今被造山带前缘逆冲体覆盖的区域,也应该是油气田产出的有利区域,即盆地外造山带花岗岩下依然是寻找油气田的重要远景区。分布于中国东部的平原区和黄海、东海及南海等陆缘海区,属于地表热流值高的“热盆”,这些盆地下对应的是裂谷型或洋壳型岩石圈,它们是在新生代时期中国东部沿海地区进入了新的构造演化阶段——大陆裂谷作用下形成的,以伴随广泛的玄武岩喷发为标志,对流地幔物质和热输入使盆地热流值升高成为“热盆”、大陆裂谷型岩石圈,乃至洋壳岩石圈(如南海中央海盆);伴随裂陷作用及伸展构造普遍发育的幔源玄武岩浆大量喷发,以及大量沉积物的快速沉积、埋藏有利于油气田的形成,其中的组分,如CO2气田中的CO2可能主要源于地幔。中国东部平原及边缘海区域是最具前景的油气田分布区之一。     

渤海湾盆地中、新生代岩石圈热结构研究

本文以浅部沉积盆地热历史恢复结果为基础,结合地热学的有关理论计算得到渤海湾盆地中生代以来不同地质时期壳幔热流配分及莫霍面温度。结果显示,渤海湾盆地在早白垩世晚期和古近纪中晚期达到两次地幔热流与地表热流之比高峰,其两期地幔热流占地表热流比例都超过65%。莫霍面温度在早白垩世晚期、古近纪中晚期及新近纪早期(仅在临清坳陷、沧县隆起和冀中坳陷)出现3次高峰,其温度分别为900～1100℃、820～900℃和770～810℃。本文的研究不仅揭示出白垩纪是渤海湾盆地岩石圈热结构的重要转型期,即由三叠纪和侏罗纪的"冷幔热壳"型转变为白垩纪以来的"热幔冷壳"型的岩石圈热结构,还揭示出渤海湾盆地在早白垩世晚期和古近纪中晚期发生两期强烈的构造裂陷作用。因此,本文的研究可以为中国东部大陆岩石圈地球动力学的研究提供地热学参数。     

中国大地构造单元新格局——从岩石圈角度的思考

以中国大陆的岩石圈岩石学结构模型和根据岩石圈动力学性质划分的克拉通型、造山带型、裂谷型、边缘海洋壳型和岛弧型5大岩石圈类型为基础,结合现今中国大陆西部挤压、东部拉张伸展的特点,提出以四川盆地、鄂尔多斯盆地和银川盆地西边界的岩石圈不连续为界,把中国大陆分为东部和西部2个一级构造单元;不同类型岩石圈为其二级构造单元,一些造山带型岩石圈的亚类为三级构造单元,并结合地质历史,简要讨论了其形成过程及其意义。     

地幔转换带:地球深部研究的重要方向

地幔转换带是联系上下地幔的纽带,对于认识整个地幔的组成和演化、地幔对流、岩石圈深俯冲及深源地震等地球深部动力学问题具有重要意义。一般认为,转换带地震不连续面主要与橄榄石的高压相变密切相关。最新的高温高压实验研究表明,地幔中非橄榄石组分的相变,如辉石和石榴子石的相变,对不连续面的深度和宽度以及转换带内的波速和密度梯度也起到很大的影响。另外地幔全岩成分、端员组分、温度和水也对相变和不连续面具有重要影响,这些精细的实验研究成果更好地解释了转换带地震不连续面一些相对局部的性质和变化,促进了我们对地球深部性质和动力学过程的了解。因为缺少直接来自地球深部的样品,而地球物理和地球化学研究也有它们的相对局限性,所以高温高压实验仍然是我们了解地球深部成分和性质的重要手段之一。     

蒙古—贝加尔地区地热特征及其地球动力学机制

蒙古—贝加尔裂谷的演化及其形成的动力学机制一直是地学界争论的焦点.至今, 对其地热学的相关研究一直比较匮乏.本文根据前人对蒙古—贝加尔及邻区的独特地貌、构造和玄武岩火山岩浆作用的研究, 并结合现今地表大地热流特征共同探讨了其地球动力学机制.根据最新大地热流分布特征表明: 蒙古地区的高热流区(>120 mW/m2)主要集中在蒙古Hangay穹窿北部Hovsgol裂谷及其周围裂谷内|贝加尔裂谷整体热流都较高, 且贝加尔东北部热流达160 mW/m2 以上(比前人报道的更高), 其中部热流也高(120 mW/m2).综合地热、地质与地球物理成果, 本文认为晚新生代的地幔柱对蒙古—贝加尔地区的形成起着重要作用.     

Formation mechanism of central-type structures in the West Pacific continent-ocean transition zone

The rotary formation mechanism of various central-type geological structures functioning in the strike-slip fault systems of the West Pacific continent-ocean transition zone is considered. This mechanism explains many tectonomagmatic processes and is confirmed by geological, geophysical, and geomorphological studies. At the same time, it is not the only possible mechanism. Examples of magmatogenic central-type ring and vortical structures in the Japan Sea segment of the West Pacific continent-ocean transition zone are given. In our opinion, the proposed geodynamic model is inscribed into the paradigm of tectonic delamination of the lithosphere developed by Yu.M. Pushcharovsky.     

从青海共和—贵德盆地与山地地温场特征探讨热源机制和地热系统

青海共和—贵德盆地及其相间山地具有盆地传导型地热资源,地温梯度大,地热勘探钻孔在基底均见花岗岩,盆缘山地隆起断裂对流型温泉呈带分布,水温高,也出露在花岗岩中.对其热源机制的认识目前存在分歧.本文对地幔型热源提出质疑,认为花岗岩放射性生热为壳内热源并提出地化依据;同时,用地热钻孔测温曲线和地球化学地热温标对热储温度和深度进行了探讨.研究结果表明,周边山地属中温地热系统,新生代断陷盆地内具高温地热系统,其钻孔井底测温已达175~180℃,是干热岩开发的优选地段.     

渭河盆地地温场分布规律及其控制因素

本文以渭河盆地地温场为研究对象,在收集补充新地热井资料及分析测试样品的基础上,通过盆地深部结构、构造特征、地温场特征、热储层特征、地热资源量等分析,建立了盆地不同岩性岩石热导率与深度关系图版,确定了盆地地温场变化规律及地热田控制因素,提出了渭河盆地地热田形成模式。评价了盆地地热资源有利区,为盆地后续的开发利用提供了理论支持。研究认为渭河盆地热地温梯度分布在2.34～5.85℃/100m之间,平均地温梯度为3.50℃/100m,代表性大地热流68.33mw/m²,地温梯度及不同深度地层温度具有东高西低、南高北低的特点。热导率总体上具有随深度的增加,逐渐增大的规律,热导率随深度增加主要受压实程度增强控制。相同深度条件下泥岩热导率最低,砂岩热导率居中、白云岩热导率最高。渭河盆地主要为层状地热田,盆地内地热通过热传导及热对流两种方式进行传递,以热传导为主。渭河盆地地热资源丰富,热储层可分为三种类型:①新生界砂岩孔隙型;②下古生界碳酸盐岩岩溶型;③断裂型。渭河盆地地热资源有利区主要分布于西安凹陷、固市凹陷。盆地地温场及地热田分布与莫霍面、软流圈上隆、岩石圈厚度减薄的深部背景...     

粤东北贝岭地热田地热地质特征及水化学分析北大核心CSCD

粤东北地区拥有丰富的低温水热型地热资源。贝岭地热田位于河源深断裂北东端,具有优越的地热地质条件,地热田内施工的钻孔(ZK1~ZK5)均揭露到了热矿水,水温48.2~77.0℃。为了深入研究地热田内的水化学特征,通过运用系统的水文地球化学分析方法,得出研究区热矿水水化学类型为低矿化的HCO_(3)-Na型,SiO_(2)含量较高,可用作理疗矿泉水。研究区地下热矿水处于水岩作用的初级阶段,热矿水中的石英和玉髓溶解度已达平衡状态。使用石英温标进行热储估算,结果表明T_(石英)=116.0~150.1℃,平均地温梯度G=12.01℃/100 m,热储循环深度H=819.33~1103.26 m。本研究为今后该区的深部找热工作提供了一定的技术支撑。     

广东惠州黄沙洞地区岩石圈热-流变结构及其热源启示

岩石圈热-流变结构研究是揭示岩石圈范围内热状态的有效手段,开展地热异常区的岩石圈热-流变结构研究可以对热源贡献进行有效约束。东南沿海地区是我国地热资源重要分布区,地表出露大量天然温泉,地热钻探揭露深部具有较高的地温梯度,然而关于其热源机制尚未有定论,且深部是否赋存干热岩资源亦不清楚。以广东惠州黄沙洞地热田为研究对象,分析岩石圈尺度温度分布和流变强度,探讨黄沙洞地热田的热源构成,分析浅部水热系统的热影响,并对干热岩资源前景进行分析。结果表明：（1）黄沙洞地热田水热活动影响下地表热通量为130.3 mW/m2,地壳热流与地幔热流值相近,表现为温壳温幔型岩石圈热结构,此外,构造活动相关热流达到了30.5~60.3 mW/m2;（2）岩石圈流变结构显示中地壳存在韧性流变层,上地壳与下地壳以脆性破裂为主,下地壳与地幔表现出流变结构耦合,为相对稳固的地壳底界;（3）黄沙洞地热田的热源以地壳构造活动产生的热源为主,地幔热源和放射性生热是主要的热源组成部分,构造热作用的主要方式包括区域深断裂的热聚敛和水热系统循环换热,两者可能通过“接力式”热传递携带热量至浅表;（4）区域深断裂的热聚敛在构造热作用中的占比是影响干热岩资源前景的关键因素。本项研究可为后续东南沿海同类型地区的干热岩资源勘查与靶区选址提供参考。     

Thermal modelling of the Larderello geothermal field (Tuscany,Italy)

We present a 3-D thermal model of the Larderello geothermal field (Tuscany) to evaluate (1) the extent and contribution of the heat transfer mechanisms (conduction vs. convection) at the intermediate-upper crust levels, (2) the variability of the heat and mass fluxes entering from below and (3) the crucial role of the formation permeability. The model, composed by three main layers, considers the upper 10 km of the crust to better constrain the simulations with experimental data from borehole, fluid inclusion studies and hypocentral distributions. Several sets of simulations were carried out with different bottom boundary temperatures and different formation permeabilities for the two deeper layers. The results indicate that the present temperature (T) and pressure distributions in the Larderello field require deep reservoir rocks with higher permeability than the overlying capping units and underlying intermediate crust. Permeability values of 1 mDarcy for the reservoir rocks are enough to allow fluid convection, if the temperature at 10 km depth is as high as 500 ± 50°C. The presence of localized zones with formation permeability 50–100 times higher than the surrounding rocks strongly favours the migration of over-pressurized fluids, which episodically break through the overburden, feeding the presently exploited geothermal fields.     

采灌条件下中低温热储温度场动态特征初探

中国四大直辖市之一的天津具有较高地温场背景,地热开采历史长、规模大,回灌式循环开采发展势头喜人。由连续开采多年的地热井井口稳定流温监测数据证实:各储层地热流体温度并没有因长期开采而出现明显变化;而由同一眼基岩回灌井、停灌前后不同时段进行的井温测试结果表明:以比热储温度低得多的原水进行回灌,虽然井管内同一井段不同时期井温有0.1～0.76℃/a的微弱降幅,但主要取水层段在一个停灌周期内的井温则呈逐月恢复势态,数据显示停灌期间回灌井区域基岩热储温度回升迅速,并在下一个回灌期来临之前即可逐渐回复至前年同期的热储原始温度水平。     

西藏日喀则市查孜地热田水化学及同位素特征研究

查孜地热田位于青藏高原西南部。通过野外地质调查及地热钻孔揭露,发现该地热田具有较好的地热资源开发潜力。对该地热田地下热水的水文地球化学及同位素特征开展研究,发现地下热水为HCO₃-Na型; 热水与冷水的离子浓度存在差异,显示二者具有不同的物质来源,但又具有一定的水力联系。热水中的δD和δ¹⁸O同位素特征表明: 该地热田地下热水的主要补给来源为大气降水和冰雪融水,补给海拔为5 652 m以上; 大气降水和冰雪融水下渗并与沿断裂破碎带向上运移的地热流体混合后形成地下热水。断裂破碎带不仅是温泉的主要通道,也是地热流体的储集场所,地热田热水在地下运移滞留至少41 a。据SiO₂地热温标估算得出,该区地下热储温度为148.18 ~153.49 ℃,天然放热量为2 264.33×10¹² J/a。     

Hydrochemical and isotopic characteristics of Chazi geothermal field in Shigatse in Tibet

Chazi geothermal field is located in Southwestern Tibetan Plateau. The geothermal potential has been ascertained by field survey and geothermal drilling. The hydrogeochemical characteristics and isotopic composition of this geothermal field show that the underground water belongs to HCO₃-Na. The difference of ion concentration between hot water and cold water shows that they have different material sources and certain hydraulic relations. The isotope analysis of δD and δ¹⁸O determines that the major source of the geothermal water in this area is meteoric water and water melt from the mountains snow and ice with the height above 5 652 m. The geothermal water was the result of the mixture of deep infiltrated meteoric water and deep-source fluid when they move along the fracture zone. The fracture zone is the main channel of hot spring and the reservoir of geothermal fluid. The migration retention time of the geothermal water in this geothermal field was at least 41 years. According to the calculated temperature of SiO₂ geothermometer, the geothermal temperature of the underground heat reservoir is about 148.18~153.49 ℃, and natural heat discharge is 2 264.33×10¹² J/a.     

Thermal history, geodynamics, and current thermal activity of lithosphere in China

The tectonic framework of China includes major and smaller-scale units that differ in age and in style of tectonomagmatic activity, the latter being related to the thermal history of the lithosphere. Heat flow in the area varies from 25 to 150 mW/m² or higher, with an average of 58±11 mW/m². It is high in active faults, rifts, and other structures of extension (or sometimes compression) subject to heating from rising lithospheric and mantle plumes. The current thermal activity in the region is controlled by the Pacific subduction beneath Eurasia in eastern China and mainly by the lateral strain and rotation of the Ordos block associated with the India–Eurasia interaction in central and western China.     

Thermal and petrological structure of the lithosphere beneath Hannuoba, Sino-Korean Craton, China: evidence from xenoliths

Deep-seated xenoliths entrained in the Hannuoba basalts of the northern Sino-Korean Craton include mafic and felsic granulites, mantle wall-rock from spinel– and garnet–spinel peridotite facies, and basaltic crystallisation products from the spinel-pyroxenite and garnet-pyroxenite stability fields. The mineral compositions of the xenoliths have been used to estimate temperatures and, where possible, pressures of equilibration, and to construct a geothermal framework to interpret the upper mantle and lower crustal rock-type sequences for the region. The xenolith-derived paleogeotherm is constrained in the depth interval of 45–65 km and like others from areas of young basalt magmatism, is elevated and strongly convex toward the temperature axis. Two-pyroxene granulites give the lowest temperatures and garnet pyroxenites the highest, while the spinel lherzolites fall between these two groups. The present-day Moho beneath the Hannuoba area is defined at 42 km by seismic data, and coincides with the deepest occurrence of granulite. Above this boundary, there is a lower crust–upper mantle transition zone about 10-km thick, in which spinel lherzolites and mafic granulites (with variable plagioclase contents) are intermixed. It is inferred that this underplating has resulted in a lowering of the original pre-Cenozoic Moho (then coinciding with the crust–mantle boundary, CMB) from about 30 km to its present-day position and was due to intrusions of basaltic magmas that displaced peridotite mantle wall-rock and equilibrated to mafic granulites. Trace element patterns of the diopsides (analysed by laser ablation-ICPMS) from the Cr-diopside series spinel lherzolites and associated layered xenoliths (spinel lherzolites and pyroxenites) indicate a fertile uppermost mantle with moderate depletion by low degrees of partial melting and little evidence of metasomatic activity. The similarity in major and trace element compositions of the minerals in both rock types suggests that the layered ultramafic xenoliths formed by mantle deformation processes (metamorphic segregation), rather than by melt veining or metasomatism.     

Shallow geothermal regime in the Perth Metropolitan Area

Exploration of Perth's geothermal potential has been performed by the Western Australian Geothermal Centre of Excellence (WAGCoE). Detailed vertical temperature and gamma ray logging of 17 Western Australia Department of Water's (DoW) Artesian Monitoring (AM) wells was completed throughout the Perth Metropolitan Area (PMA). In addition, temperature logs from 53 DoW AM wells measured in the 1980s were digitised into LAS format. The logged data are available in the WAGCoE Data Catalogue.

Analysis of the gamma ray logs yielded the first estimates of radiogenic heat production in Perth Basin formations. Values by formation ranged between 0.24 and 1.065 μW m^?3. The temperature logs provide a picture of true formation temperatures within shallow sediments in the Perth Basin. A three-dimensional model of the temperature distribution was used to produce maps of temperature at depth and on the top of the Yarragadee aquifer.

The temperature data were interpreted with a one-dimensional conductive heat model. Significant differences between the model and the observations was indicative of heat moving via non-conductive mechanisms, such as advection or convection. Evidence of non-conductive or advective heat flow is demonstrated in most formations in the region, with significant effects in the aquifers. Average conductive geothermal gradients range from 13°C km^?1 to 39°C km^?1, with sandstone formations exhibiting average gradients of approximately 25°C km^?1, while insulating silt/shale formations show higher average gradients of over 30°C km^?1.

To produce preliminary heat flow estimates, temperature gradients were combined with thermal conductivities measured elsewhere. The geometric mean heat flow estimates range between 64 mW m^?2 to 91 mW m^?2, with the standard deviation of the arithmetic mean heat flow ranging between 15 and 23 mW m^?2.

The study characterises the shallow temperature regime in the Perth Metropolitan Area, which is of direct relevance towards developing commercial geothermal projects.     

中国大陆地区温泉分布的深部热背景

温泉是地热资源的直接显示.本文通过收集中国大陆温泉数据,对温泉分布进行了分区,并从热岩石圈厚度、莫霍面深度、岩石圈热结构和居里面深度等角度出发,揭示了温泉分布与深部热背景之间的联系.以泉水温度为依据将温泉定义为低温泉(25℃≤T＜50℃)、中温泉(50℃≤T＜75℃)和高温泉(T≥75℃).根据大地构造、区域地理和地热...