冀东陆壳热结构─—由岩石学模型推导

本文根据变质岩矿物对的平衡热力学研究结果，提出冀东地区早前寒武纪陆壳平均地温分布曲线，并讨论现代陆亮地温曲线的两种可能形态．早前寒武纪在相当于中、下地壳的部分，地温的平均梯度约为７．３℃／ｋｍ，它预示了对流热传输占有重要地位（约占６５％）．基于传导热传输的假设，现代地温分布是一条平滑的曲线，而基于中地壳是一个含水的低速层以及对流热传输的假设，现代地温分布则可能是一条折线．退变质作用引起的放热与扩容可能是诱发地震的能量来源之一．     

中国东部上地幔热结构——由岩石学模型推导

中国东部新生代玄武岩中丰富的超镁铁岩包体,是玄武岩浆喷出地表时取出的上地幔岩石标本。本文汇集了405个超镁铁岩中辉石的温压数据,提出了更为情确的新的辉石地温。它所代表的上地幔平均地温梯度为3.3℃/km,远小于由传导热模型推导的地温梯度(约14℃/km),暗示了对流热传输占有重要位置。粗略估算表明,对流热传输与传导热传输的贡献分别为79％与21％。上地幔热结构的扰乱是新生代中国东部发育大陆裂谷构造与强烈玄武岩火山活动这一构造热事件的重要表现。基于辉石地温与地表热流值推导的现代地温场的对比,提出了Moho可能是一个次级的热边界层,中国东部现代地温场与岩石圈热结构,可能仍主要反映了晚第三纪—第四纪构造热扰乱事件的结果,或者说岩石圈的冷却才刚刚开始。     

海拉尔盆地地温分布及控制因素研究

根据大量钻孔测温资料和实测热导率资料分析了海拉尔盆地地温分布状况,现今地温梯度变化在2.50℃/100m至4.0℃/100m之间,平均为3.0℃/100m,现今大地热值为42.15~63.86 mWm-2,平均约为55.00mWm-2,明显较松辽盆地低,表明海拉尔盆地是一个中温盆地。海拉尔盆地大磨拐河组底面和南屯组底面地温分布具有南高北低的特点。现今地温对油气生成有重要的控制作用,南部凹陷南屯组热演化程度高,普遍处于成熟生油阶段,南屯组是海拉尔盆地的主力生油层位,南部凹陷是海拉尔盆地主要找油区。海拉尔盆地与松辽盆地壳幔结构存在显著的差异。海拉尔盆地现今地温场主要受地壳厚度、基底结构、基底埋深及盆地构造等因素的控制。     

地温测量在地热勘查中的应用

地温测量是研究地温场分布最直接的方法。地热热源的强度与分布,直接影响地壳表层土壤温度场的分布,特别是存在热储层、热运移通道等都会使地温场的分布产生异常。在研究区16个民井和32个钻孔中进行地温测量,分析地温场分布状况以及地下热水活动规律,效果明显。结果表明研究区浅孔与深孔地温场平面特征一致,越接近东北角地温越有增加的趋势,而且地温异常区呈NNE向条带状分布,宽度约700 m,与NNE向断裂展布方向一致,地温最高点位于NW向断裂与NNE向断裂交汇处。研究区在纵向上地温分布特征差异性明显,地下热水分布范围较小,具有一定局限性,主要受构造断裂、岩溶发育程度等控制,温度低的地下水大量涌入导致地下水温降低,地温梯度出现异常;这种地温梯度异常现象也说明了研究区地下热水主要储存于灰质白云岩或角砾岩的裂隙溶洞中,裂隙、岩溶成为地下热水良好的运移通道。地温测量方法圈定了研究区地热异常区范围,为进一步勘查地热提供了重要的依据。     

基于多种估算方法的湖南省现今地温梯度综合确定

湖南省目前地热井多为深度较小(多在500m以浅)的热对流型,用地热井测温数据求取的地温梯度一般偏大很多。为解决对流型地热测得的地温梯度偏大问题,本文采用地热温标、管道模型及基于生热率的深部地温反推法等地温梯度估算方法,综合确定了湖南省现今的地温梯度。结果显示,湖南省高地温场大致沿中部的白马山岩体、沩山岩体、幕阜山—黄龙山岩体一线和湖南省东南部分布,地温梯度大于3.0℃/100m;5000m深度、6000m深度沩山岩体、热水圩一带的最高温度分别达到了218.69℃、216.70℃和258.99℃、256.60℃。深大断裂与多块体接合部位的构造形态相配合,使湖南省中部构造交汇带处于张开性的构造环境,有利于大气降水的深循环与深部热物质的上侵,是形成湖南省中部高地温场的主要原因。湖南省东南部是西太平洋板块俯冲与回撤的前缘,处于江南造山带与华夏板块的接合带,有利于大气降水的深循环与深部热物质的上侵;同时高放射性生热率的铀矿床、矿点也提供了较高的地壳热量,是形成湖南省东南部高地温场的主要原因。地温梯度及地温场的科学界定,为湖南省下一步寻找高温地热资源指明了方向。     

前寒武纪大陆地壳地质构造演化研究进展与问题

前寒武纪地质构造是地球系统科学研究的一个承前启后的重要组成部分,现存最古老的固体地球物质是38亿年前的大陆长英质岩石。以地质构造热事件为标志确认早中太古代已有30亿年年龄值的大陆克拉通化,而新太古代末大陆地壳已出现普遍的克拉通化。由深变质作用岩石测得的p-t值推断当时地温梯度与现今大陆稳定区相似,大规模的陆壳区断块已具基本刚性特征,使板块构造运动模式基本适用于太古宙地壳演化。古元古代末陆壳普遍隆升和遭剥蚀,陆壳生长作用导致形成大陆区块上的裂谷型坳拉槽系。中元古代起,世界约于18亿年前近乎同时出现不变质的沉积盖层,使前寒武纪明显必需划分为早、晚前寒武纪两大阶段。华北克拉通区是世界大陆克拉通地壳的组成部分,与世界各大陆克拉通演化有很好的可对比性,在前寒武纪超级大陆重建中有一定位置。在现今阶段研究基础上,对华北克拉通区提出了几个前瞻性的基础研究课题,应予深入探索。     

豫西传导型与对流型地热异常实例

平顶山十三矿位于断块构造的凸起部位,矿井地温场与基底起伏有密切关系,地温异常的形成和地温场的变化是地壳深部的均匀热流上升至浅部时,因构造造成的岩石热导率侧向差异而形成的,是不均一传导传递的结果。梁北一井田地温场变化特点则与地下水对热量的对流传递有关,在岩溶较发育、承压水上升活动强烈的构造部位,地温梯度增高,形成地温异常.按照起决定作用的热传递方式划分矿山地温类型,前者属传导型地温场,后者属对流型地温场。     

5m地温测量在地热勘探中的应用

本文介绍了地热地质勘探中一种有效方法。通过对地热上升机理和浅层地温变化的研究,结合施工,总结出5m地温测量法。该法可用于盆地增温—对流型和构造—对流型地热田勘探,也可用于寻找隐伏断裂。该方法在山东省曲阜市地热地质勘查中,取得了较好的效果。     

新郑矿区钻孔地温特征及其受控机制

地温是影响煤炭开采的重要地质因素之一。通过对新郑矿区911钻孔稳态测温及理论分析表明,911孔位于新郑矿区主体构造滹沱背斜的轴部,具有高热流、高梯度的温度分布特征。钻孔的温度分布主要受构造起伏的影响和地下水垂向对流的控制双重作用。矿区构造起伏使来自地壳深部的热流重新分配并向背斜轴部集中,从而导致911孔出现高热流高梯度的温度特征;地下水的垂直对流运动使钻孔的温度分布进一步产生差异性。     

鄂尔多斯盆地渭北隆起西南缘奥陶系热演化史恢复与生烃史——以麟游-旬邑地区为例

本文应用古地温恢复法及盆地模拟法,恢复鄂尔多斯盆地渭北隆起西南缘奥陶系最大古地温梯度、热演化史和生烃史。根据钻孔测温曲线求得渭北隆起现今地温梯度为3.12℃/100m。该区在二叠纪和三叠纪进入快速沉降阶段,早侏罗世早白垩世进入缓慢沉降阶段,晚白垩世以来进入抬升剥蚀阶段,剥蚀厚度在1100~1300 m。旬邑地区奥陶系烃源岩在早二叠世约270 Ma进入生油窗,晚三叠世约210 Ma进入成熟生油阶段。晚侏罗世约150 Ma开始大量生气,在早白垩世末期96 Ma左右,地层达到最大埋深及最高古地温,达到生气高峰。热史恢复及模拟结果表明旬邑地区早白垩世地温梯度最高可达到5.0℃/100 m,是主要生气期。     

The Thermal Structure of the Upper Mantle in Eastern China——Inferred from the Petrological Model

Cenozoic basalt in eastern China contains abundant ultramafic xenoliths which are specimens of pyrolitesreleased during basaltic magma eruption. A total of 405 P-T data of pyroxene in the ultramafic rocks have beencollected, which present a more precise pyroxene geotherm. The average geothermal gradient in the upper man-tle represented by the pyroxene geotherm is about 3.3℃ / km, which is much less than that derived from theconductive thermal model (≈14℃ / km), implying the great significance of convective heat transfer. The calcu-lation shows that the contributions of convective and conductive heat transfers are 79% and 21%, respectively.The perturbation in the thermal structure of the upper mantle is an important manifestation of thetectonothermal event of Cenozoic continental rifting and intense basaltic volcanism in eastern China. Based onthe pyroxene geotherm and its comparison with the current geothermal field derived from the measurements ofthe surface heat flows, it is suggested that the Moho may be a secondary thermal boundary. The currentgeothermal field and the thermal structure of the lithosphere in eastern China may mainly reflect the result ofthe tectonothermal disturbance in the Neogene-Quaternary, in other words, the lithosphere has just begun toCool.     

辽宁大民屯凹陷地热资源形成条件分析

大民屯凹陷是新生代陆相凹陷盆地,其地层、构造、岩浆岩等地质背景具备传导性地热的良好成矿条件,热源主要为幔源热,储热层为沙河街组砂砾岩层段层状热储,盖层为第四系、新近系馆陶组、明化镇组和部分古近系东营组泥岩段地层.凹陷内基底断层及多期次级断裂形成了地热田良好的导热和导水通道.新近系平均地温梯度2.9℃/100 m,古近系平均地温梯度3.18℃/100 m,一定深度下的地下热水可以达到理想温度,具备地热开发条件.     

Thermal perturbation during charnockitization and granulite facies metamorphism in southern India

Abstract We have deduced the steady-state lithospheric geotherm at c. 1 Ga in the south Indian shield area using the available data on the concentration of radioactive elements, and the P-T conditions of Proterozoic mantle xenoliths in the south Indian kimberlites as constraints. The geotherm was adjusted back to 2.5 Ga by keeping the surface temperature constant and calculating the temperature change at the top of convecting upper mantle. The reduced or mantle heat flux, which was treated as an adjustable parameter, was 20.9–21.3 mW/m² at 1–2.5 Ga. Comparison of the calculated steady-state geotherm with the available P-T data of the Archaean (c. 2.5 Ga) charnockites and granulites from southern India suggests that the granulite facies metamorphism in this region had resulted from a major thermal perturbation, which was c. 400° C at 25 km. Seismic tomographic and gravity data essentially preclude any significant magma underplating of the granulitic crust in southern India. Previous workers have suggested that the formation of charnockites in this region was associated with copious CO₂ influx from a deep-seated source, possibly the mantle. In this work, we have evaluated both the transient and steady-state thermal effects of the heat convected by CO₂ outgassing from upper mantle. It is shown that the thermobarometric array of charnockites and granulites can be produced by the convective perturbation of the steady-state geotherm, and that a flux of CO₂ of ±90 mol/m² yr (corresponding to Darcy velocity of ±0.30 cm/yr) for a period of ±30 Ma was needed to produce the required perturbation. This is c. 150 times the average CO₂ flux through the tectonically active area of the Earth's crust at the present time. There is, however, an uncertainty of a factor of 3 in this value. Seismic tomographic and gravity data independently suggest thickening of the crust beneath the granulite terrane compared with the adjacent Dharwar craton. This suggests thermal perturbation due to overthrusting as a major potential cause for the granulite facies metamorphism in south India. Overthrusting of a 30–35-km-thick thrust block was needed to produce the required thermal effect. The estimated thickness of the original crust from geobarometric and seismic tomographic data south of the orthopyroxene isograd or ‘transition zone’is compatible with the emplacement of a thrust block of this magnitude. However, the latter fails to match the estimated pre-uplift crustal thickness at the transition zone, if it is assumed that the crust has not thinned by non-erosional processes since the Archaean. Thus, we propose a combination of overthrusting and CO₂ fluxing from a deep-seated source as the cause for the formation of charnockites in this zone. The required focusing of CO₂ in this case is c. 40% of that estimated in the model where CO₂ fluxing was considered to be the sole reason for thermal perturbation. This combined thrusting—CO₂ fluxing model also helps explain the development of patchy charnockites in the transition zone from amphibolite facies rocks.     

A rifted tectonic setting for hercynian high-thermal gradient metamorphism in the pyrenees

Hercynian regional metamorphic terrains in the Pyrenees contain evidence of very high-temperature gradients within the crust during metamorphism, with temperatures as high as 700°C attained at 10–12 km below the surface. Stable isotope studies demonstrate that the crust was simultaneously flushed by marine fluids to at least this depth. The absence of any evidence for crustal collision, and the Upper Palaeozoic stratigraphic record for the area, suggest that the tectonic setting for the metamorphism was a zone of continental rifting associated with strike-slip movement. In this zone anatexis occurred at two distinct levels: Cambro-Ordovician pelites at the base of the Palaeozoic sedimentary pile melted to produce per-aluminous magmas, while in the lower Hercynian crust, very large-scale melting generated voluminous granodioritic magmas which then invaded high-structural levels. The thermal structure of the Hercynian crust was profoundly influenced by both convective and advective heat transfer, due to movement of surface derived aqueous fluids, and intrusion of magmas.     

汉诺坝地区上地幔尖晶石—石榴石相转变带温压条件

根据汉诺坝尖晶石石榴石二辉辉石岩包体矿物成分新资料和前人的尖晶石石榴石二辉橄榄岩包体矿物成分资料,运用斜方辉石Ｃａ溶解度温度计和斜方辉石－石榴石Ａｌ分配压力计,计算了尖晶石—石榴石相转变带的温度和压力条件,首次获得了汉诺坝地区的新生代古地温曲线。尖晶石石榴石二辉辉石岩包体代表的温度范围为９３０～９７８℃,压力范围为１４２～１６５ＧＰａ：尖晶石石榴石二辉橄榄岩包体代表的温度范围为９９１～１１１０℃,压力范围为１５８～２１６ＧＰａ,与最新的实验结果基本吻合。地温曲线沿大洋地温曲线（曲线方程为ｔ＝２５２４＋８９７４７８ｐ－１８３０８ｐ２）上方近平行延伸。推测汉诺坝玄武岩的起源深度至少为７０ｋｍ。二辉辉石岩包体来自较冷的岩石圈,而二辉橄榄岩来自岩石圈与软流圈的过渡带,并且表明后者的地温梯度以对流热地温梯度为主。     

冀北太古代花岗质片麻岩的成因

冀北是华北克拉通早前寒武纪变质基底的主要出露地区之一。分布于承德-滦平和赤城-张家口地区的新太古代花岗质片麻岩主要由英云闪长岩、奥长花岗岩、花岗闪长岩和二长花岗岩(TTGM)组成,构成了低钾、中钾和高钾钙碱性三个岩石化学系列。二长花岗质片麻岩的LA-ICP-MS锆石U-Pb和Lu-Hf同位素特征揭示其岩浆结晶年龄为2509±10Ma。全岩岩石化学、Sm-Nd同位素和锆石Lu-Hf同位素研究表明:(1)低钾钙碱性系列的岩石形成于拉班玄武质岩石的低度部分熔融;(2)中钾钙碱性系列岩石主要形成于玄武质岩石和杂砂岩的部分熔融,局部存在英云闪长质片麻岩的部分熔融;(3)高钾钙碱性系列的岩石形成于以高钾中酸性火山岩为主要成分的杂砂岩的部分熔融。结合近年来冀北早前寒武纪地质研究成果,这些太古代花岗质片麻岩全岩Sm-Nd同位素和锆石Lu-Hf同位素特征揭示~2.7Ga是本区太古代地壳的主要生长期。在新太古代发生了大规模的火山喷发,火山物质形成后不久发生部分熔融形成花岗质岩浆,接着发生变质、变形作用。这些花岗质片麻岩的形成与南美洲西海岸的构造-岩浆活动特征有类似之处,可能反映了太古代末期冀北地区从活动大陆边缘地壳增生、加厚到弧后伸展转化的动力学背景。     

黑龙江省东部早前寒武纪基底及矿床成矿系列划分

黑龙江省东部早前寒武纪基底具有构造复杂、岩浆活动频繁、变形变质强烈、成矿活动特殊等特点.研究其基底地质特征,探讨与其关系密切的矿床成矿系列类型及其成矿模式、演化特征,并开展典型矿床研究,对深化黑龙江省早前寒武纪矿床特征认识及开展贵金属、有色金属及非金属（石墨、夕线石）矿产勘查基地优选,具有十分重要的战略指导意义.     

Secular cooling and crystallization of partially molten Archaean continental crust over 1 Ga

The protracted tectonic and magmatic record of cratons over the Archaean Eon has been classically interpreted in terms of long-lived shallow-dipping subduction or repeated mantle plumes. In this paper, we use the 1D conductive heat equation to model the evolution of the geotherm of a generic felsic-dominated Archaean cratonic nuclei solely considering the secular decay of radioactive isotopes (²³⁸U, ²³⁵U, ²³²Th, and ⁴⁰K), responsible for heat production in the crust. Using a range of plausible parameters for crustal thickness, lithospheric thickness, and surface heat flux, this modelling shows that Archaean crust was characterized by an initially high geothermal gradient at 3.5 Ga, with a Moho temperature close to 900 °C, and that it might have remained partially molten for about one billion years. The existence of a partially molten crust for an extended period of time offers an alternative option to shallow-dipping subduction or repeated mantle plumes for the understanding of the peculiar tectonic evolution of Archaean cratons marked by (i) protracted high-temperature metamorphism and magmatism associated with crustal differentiation, and (ii) widespread deformation characterized by structural domes attributed to the development of crustal-scale gravitational instabilities.     

内蒙古喀喇沁地区早中生代闪长岩中麻粒岩捕虏体矿物化学及变质温压条件

在内蒙古东部喀喇沁地区早中生代大营子闪长岩中首次发现基性麻粒岩捕虏体.初步研究表明它们不同于华北克拉通地表出露的前寒武纪麻粒岩.根据其主要造岩矿物斜方辉石、单斜辉石、黑云母及斜长石的电子探针分析结果, 重点研究了各主要造岩矿物的化学成分特点, 并讨论了麻粒岩捕虏体的变质作用温压条件.研究结果表明, 捕虏体岩石的变质作用已达麻粒岩相, 其变质作用条件约为850~900 ℃, 0.6~1.0 GPa.这些麻粒岩捕虏体反映了研究区早中生代下地壳的组成特点, 为恢复该区早中生代深部地壳结构提供了依据.      

安徽长山地热初探

合肥盆地西界长山隆起,位于安徽省霍邱县西北。地壳减薄上地幔隆起是地热形成的地质背景,适当厚的高热阻盖层和高热导率的基底相配置是地热形成的基本原因。两条导水断裂是良好的导热通道,至使长山地热-400m地温达40℃以上,地温梯度达4．27℃／100m～5．46℃／100m,安徽长山地热是基底隆起聚热型,若科学合理勘探开发,将会给皖西地区带来十分可观的经济和社会效益,同时对省会经济圈建设和大别山地质公园旅游业发展意义重大。