阿尔泰山南缘白垩纪以来的剥露历史和古地形恢复

应用裂变径迹技术研究阿尔泰山南缘中新生代以来的隆升剥露历史,并对古地形进行恢复。对所获得的11个磷灰石样品的裂变径迹年龄分析表明,裂变径迹年龄变化分布于99.1~43.7 Ma之间。该地区晚白垩世以来平均视剥露速率为0.050 mm/a。热史模拟结果表明,阿尔泰山南缘自白垩纪以来经历了多期冷却剥露历史:早白垩世至晚白垩世晚期(约120~75 Ma),剥露速率为0.044 mm/a;晚白垩世晚期至始新世(约75-70~50 Ma),剥露速率为0.070 mm/a;中新世以来(约20-15 Ma~现今),剥露速率为0.081 mm/a。对研究区进行古地形恢复显示,自白垩纪(120 Ma)至今,平均剥露幅度达约5 km,古地形海拔降低约0.8 km。阿尔泰山南缘白垩纪以来古地形海拔仅在17.5~50 Ma期间保持基本稳定,其他阶段均有降低的趋势。早白垩世的构造抬升与蒙古-鄂霍茨克海最后阶段的闭合以及西伯利亚板块和中朝-蒙古板块的最终收敛和碰撞有关;晚白垩世晚期至始新世的构造活动则是受拉萨地块、Kohistan-Dras岛弧增生的远距离影响;中新世以来快速隆升可能与印度板块与欧亚板块碰撞的远程效应有关。     

Three-dimensional thermo-mechanical modeling of the Cenozoic uplift of the Tianshan mountains driven tectonically by the Pamir and Tarim

We develop a three-dimensional thermo-mechanical model as an approximate representation of the lithosphere of the Tianshan orogenic belt and adjacent geological units for simulating the uplift mechanism of the Tianshan mountains in the Cenozoic. We apply a velocity boundary condition approximating the northward push of the Pamir and Tarim against the Tianshan block to derive lithospheric deformation of the model. In particular, we investigate systematically the influence of gravity-induced creep deformation on mountain uplift. Our modeling results indicate that: (1) the modeled topographic pattern coincides well with the actual topography, implying that the tectonic push of the Pamir and Tarim can cause significant uplift of the Tianshan mountains; (2) the lithosphere of the Tianshan mountains is mechanically weaker than that of the platforms to the south and north of the Tianshan orogenic belt; and (3) the gravity-induced creep deformation has a significant influence on the process and elevation of mountain uplift. Therefore, when subjected to the tectonic compression resulting from the northward push of the Pamir and Tarim, the relatively weak lithosphere of the Tianshan mountains would deform easily and hence absorb more shortening, resulting in lithospheric thickening and consequent mountain uplift.     

构造事件的沉积响应—建立青藏高原大陆碰撞、隆升过程时空坐标的设想和方法

沉积盆地的地层形态、岩相类型以及空间配置样式是构造事件的重要标识.沉积序列中特征岩石组分的出现标志着毗邻造山带隆升的初始启动时间,与物源区地层单元垂向叠置序列相反或相同的岩屑组分剖面分布则是幕式构造旋回的反映.在前陆盆地中砾石层的出现被认为是冲断岩席活动的记录,而在断陷盆地和走滑拉分盆地中通常可识别出100m级的向上变粗和向上变细的旋回层,它们被解释为构造高地重复隆升和溯源侵蚀的结果.最近的研究工作表明,急剧的构造沉降主要是通过细粒级河湖相沉积补偿的,广泛的砾岩进积发生在构造活动的平静期.构造驱动的山脉隆升表现为砾岩地层呈楔状体,纵向河流水系发育;重力均衡回返所导致的山系隆升则形成以横向河流水系为主的板状砾岩沉积.从青藏高原腹地、周缘和外延海洋盆地的沉积记录中可获取重大构造变革时期的信息,也许是解决目前有关印度与亚洲大陆碰撞、高原隆升等时性或穿时性以及限定陆内变形调节机制的一个重要手段.     

构造事件的沉积响应——建立青藏高原大陆碰撞、隆升过程时空坐标的设想和方法

沉积盆地的地层形态、岩相类型以及空间配置样式是构造事件的重要标识，沉积序列中特征岩石组分的出现标志着毗邻造山带隆升的初始启动时间，与物源区地层单元垂向叠置序列相反或相同的岩屑组分剖面分布则是幕式构造旋回的反映，在前陆盆地中砾石层的出现被认为是冲断岩席活动的记录，而在断陷盆地和走滑拉分盆地中通常可识别出100m级的向上变粗和向上变细的旋回层，它们被解释为构造高地重复姓升和溯源侵蚀的结果，最近的研究工作表明，急剧的构造沉降主要是通过细粒级河湖相沉积补偿的，广泛的砾岩进积发生在构造活动的平静期，构造驱动的山脉隆升表现为砾岩地层呈楔状体，纵向河流水系发育；重力均衡回返所导致的山系隆升则形成以横向河流水系为主的板状砾岩沉积，从青藏高原腹地、周缘和外延海洋盆地的沉积记录中可获得取重大构造变革时期的信息，也许是解决目前有关印度与亚洲大陆碰撞、高原隆升等时性或穿时性以及限定陆内变形调节机制的一个重要手段。     

晚新生代以来青藏高原东缘的剥蚀过程:来自裂变径迹的证据

本文以青藏高原东缘的三级地貌(川西高原、龙门山和四川盆地)单元为基础,利用裂变径迹定年数据分区块研究了该地区的晚新生代以来的剥蚀速率。研究结果表明,晚白垩世以来青藏高原东缘经历了一个由平缓到突然加速的剥蚀过程,其转折点为中新世。在整个时间段内的平均剥蚀速率,川西高原为0.26mm/yr,龙门山为0.72mm/yr,四川盆地为0.20mm/yr。龙门山的剥蚀速率大约是川西高原的2.8倍,间接反映边缘山脉的隆升并不等同于高原内部的隆升,边缘山脉的隆升可能是构造隆升和剥蚀隆升相叠加的结果。     

同位素热年代学在页岩气勘探开发中的应用:以华南地区为例

随着同位素热年代学理论体系、分析测试和模拟技术的不断完善,同位素热年代学已成为基础地质和常规油气勘探领域研究不可或缺的热点学科,但对于其在页岩气勘探开发地质评价领域中的系统应用还关注较少.通过对页岩气勘探开发综合评价体系及同位素热年代学相关理论分析,结合近年来华南地区多套页岩层系的勘探开发实践,指出同位素热年代学在页岩地层对比,页岩烃源评价中的生排烃史和构造热演化史、储集特征、保存条件评价中的核心指标（抬升剥蚀时间、剥蚀量的恢复及断裂活动期次）以及页岩可压性等多个方面的研究均可作为有效技术手段,研究表明同位素热年代学在页岩气勘探开发领域应用前景极为广阔.      

矿床保存变化研究的热年代学技术方法

成矿后矿床的保存与变化是矿床地质研究的重要组成部分,但研究程度不高,至今仍属于薄弱环节。矿床的保存与其隆升剥露密切相关,深入细致研究恢复矿区矿床的隆升和剥露历史,是揭示矿床保存变化的一种重要途径。本文重点论述研究矿床保存变化的技术方法,通过综合应用裂变径迹、(U-Th)/He、~(40)Ar-~(39)Ar年代学以及La-ICP-MS、锆石U-Pb定年等多种技术手段,研究成矿期次、构造活动期次以及二者间的联系,定量计算不同矿区、不同矿体、不同部位、不同时间的冷却隆升速率、隆升幅度、剥蚀速率和剥蚀量,探讨矿床保存深度与剥蚀量间的关系,总结不同时代、不同矿区矿床保存-变化过程,建立新的矿床地质-保存环境模型,完善矿床预测的综合示踪标志,最终预测不同矿区、不同地段隐伏矿床可能的产出深度,给出矿床可能已经被剥蚀殆尽的区段或地段,为深部找矿和区域成矿潜力评价提供依据。本文可为地质工作者的相关应用提供借鉴和手段。     

盆山关系研究的基本思路、内容和方法

盆地和造山带作为大陆岩石圈表面发育的两个基本构造单元,在空间上相互依存,在物质上相互转换和在地表形态上相互调整、均衡,两者具有密切的耦合关系。不同时期原始盆山结构、山脉变形样式、盆地充填格架及主要构造带、构造地块展布是盆山关系研究的几何学问题;山盆之间的叠加、转换和迁移历史,山脉基底和盖层剥露过程、折返机制,隆升过程,盆地的沉降方式、沉积记录和物源类型,造山带剥蚀物质的去向,山脉剥蚀量,造山带的增生方式等是盆山关系研究的运动学问题;盆山系统反映出的造山过程、区域动力学背景、深部流变学机制和调整过程及盆山演化动力模拟是盆山关系研究的动力学问题和最终目标。盆山关系研究的内容可初步确定为,不同时期的盆山几何配置关系,盆地层序地层序列与多幕构造控制关系,盆地沉积物物源与山脉剥露过程关系,盆地沉降与山脉隆升关系,地表过程与构造作用关系,盆山系统演化动力学。     

New evidence on the Neogene uplift of South Tianshan: constraints from the (U–Th)/He and AFT ages of borehole samples of the Tarim basin and implications for hydrocarbon generation

We identified a Neogene rapid uplift-denudation event of the South Tianshan based on apatite (U–Th)/He and apatite fission track (AFT) ages in Tertiary rocks of the Tarim basin, using borehole samples. The (U–Th)/He thermochronology can be used to reveal the tectono-thermal events with lower temperature than that of AFT thermochronology and has not been used previously to study the uplift of the Tianshan Mountain. Using these data, we show the relationship between the uplift of the South Tianshan and the subsidence/deposition of the northern Tarim basin during the Neogene. The apatite helium ages reveal the migration of uplift, erosion and deposition in the northern Tarim basin. A rapid uplift of the South Tianshan during the Miocene and a corresponding rapid subsidence in the northern Tarim basin occurred. However, in the Pliocene, the Kuqa Depression and South Tianshan uplifted and eroded at the same time and in turn provided the detrital source rocks for the Northern Uplift of the Tarim basin. In contrast to earlier studies, we arrive at the conclusion that the South Tianshan experienced rapid uplift in the Miocene based on (U–Th)/He data of apatite obtained from borehole samples collected in the Tarim basin itself, and not from the bordering mountain chain. Combined apatite (U–Th)/He and fission track thermochronometry enables reconstruction of thermal histories of sedimentary rocks between 40 and 120°C, and this has implications for the generation of liquid hydrocarbon in the 65–120°C range in the basin. Thermal and burial histories of typical samples were also modelled to show the rapid uplift in our study. Our works not only provide a new evidence for the South Tianshan uplift but also indicate that there is a coupling between uplift and subsidence in the South Tianshan and adjacent northern part of the Tarim basin, which controlled hydrocarbon accumulation in the Kuqa Depression and Northern Uplift of the Tarim basin.     

宁武盆地中-新生代构造演化的裂变径迹证据

为深入研究宁武盆地中-新生代的构造演化及煤层气资源的赋存条件,采集样品进行裂变径迹测试。锆石裂变径迹年龄为156～139 Ma,磷灰石裂变径迹年龄为97～47 Ma。宁武盆地中-新生代的构造演化历史可分为3个阶段。晚侏罗世(156 Ma),盆地两翼的岩体开始缓慢隆升,核部坳陷沉积,到早白垩世晚期(100 Ma),宁武盆地古地温达到最高,烃源岩达到了生气高峰期。白垩世晚期-古新世(79～59 Ma),快速抬升剥蚀。之后,虽有短暂埋藏,但总体处于隆升状态。渐新世晚期(40～30 Ma)以来快速抬升到现今位置。宁武盆地抬升剥蚀具有空间上的不均衡性。北东部抬升剥蚀早于南部,周缘岩体隆升剥蚀速率大于核部。宁武盆地是在中生代山西地块上形成一系列雁行状排列的复背斜和复向斜的构造背景下,新生代受印度洋板块挤压欧亚大陆,两翼山体强烈抬升推挤作用形成,属于华北克拉通区域构造事件的响应。     

柴西北地区碎屑锆石裂变径迹年龄记录的阿尔金山早新生代隆升事件

阿尔金山新生代隆升历史一直倍受关注,大量热年代学数据显示,渐新世(40~30 Ma)以来发生阶段性隆升,而新生代初期隆升的热年代学记录极少。柴达木盆地西北地区(柴西北地区)新生界碎屑锆石裂变径迹年龄研究表明,其物源区单一且在新生代早期古新世中晚始新世(65~50 Ma)发生快速隆升剥露,为该区提供陆源碎屑。前人通过物源分析发现,柴西北时期的碎屑物主要来源于阿尔金山。同时,该区路乐河组下干柴沟组沉积地层残余厚度及沉积相特征表明,此时(65~50 Ma)阿尔金山存在一次短暂抬升,但幅度较小,与盆地高差不大,使柴西地区地形东高西低、北高南低。结合前人研究成果,本研究锆石裂变径迹热年代学数据以及沉积学指标所记录的阿尔金山东段65~50 Ma构造隆升事件,是对新生代印度欧亚板块碰撞的最初响应,也为青藏高原新生代隆升具有南北同步性提供了新的证据。     

青藏高原东北缘西秦岭新生代抬升-天水盆地碎屑颗粒磷灰石裂变径迹记录

天水盆地位于青藏高原东北缘六盘山与西秦岭二重要构造带交汇处,该盆地充填较完整晚新生代沉积序列记录着该区构造变形历史,因此对该盆地沉积记录的研究对探讨青藏高原东北缘晚新生代构造活动事件具有重要的意义。通过对天水盆地晚新生代砂岩和含砾砂岩地层中碎屑颗粒磷灰石裂变径迹热年代学研究,推断23.7Ma左右天水盆地北部沉积物源区西秦岭发生了一次与青藏高原隆升有关的构造—热事件,该事件可能导致天水盆地的形成,并开始接受新近系冲积相沉积。约14.1Ma左右天水盆地物源区再次发生构造活动,使西秦岭剥露速率加快和盆地进一步拗陷广泛接受河湖相沉积。通过对剥蚀速率的估算,得出天水盆地沉积记录的23.7Ma和14.1Ma西秦岭北部快速抬升事件的平均剥蚀速率分别达0.34mm/a和1.05mm/a。      

Denudation history of the Snowy Mountains: Constraints from apatite fission track thermochronology

Apatite fission track thermochronology from Early Palaeozoic granitoids centred around the Kosciuszko massif of the Snowy Mountains, records a denudation history that was episodic and highly variable. The form of the apatite fission track age profile assembled from vertical sections and hydroelectric tunnels traversing the mountains, together with numerical forward modelling, provide strong evidence for two episodes of accelerated denudation, commencing in Late Permian—Early Triassic (ca 270–250 Ma) and mid‐Cretaceous (ca 110–100 Ma) times, and a possible third episode in the Cenozoic. Denudation commencing in the Late Permian—Early Triassic was widespread in the eastern and central Snowy Mountains area, continued through much of the Triassic, and amounted to at least ～2.0–2.4 km. This episode was probably the geomorphic response to the Hunter‐Bowen Orogeny. Post‐Triassic denudation to the present in these areas amounted to ～2.0–2.2 km. Unambiguous evidence for mid‐Cretaceous cooling and possible later cooling is confined to a north‐south‐trending sinuous belt, up to ～15 km wide by at least 35 km long, of major reactivated Palaeozoic faults on the western side of the mountains. This zone is the most deeply exposed area of the Kosciuszko block. Denudation accompanying these later events totalled up to ～1.8–2.0 km and ～2.0–2.25 km respectively. Mid‐Cretaceous denudation marks the onset of renewed tectonic activity in the southeastern highlands following a period of relative quiescence since the Late Triassic, and establishes a temporal link with the onset of extension related to the opening of the Tasman Sea. Much of the present day relief of the mountains resulted from surface uplift which disrupted the post‐mid‐Cretaceous apatite fission track profile by variable offsets on faults.     

天山北麓晚新生代沉积及其新构造 与古环境指示意义 *

天山山脉隶属中亚造山带,晚新生代时期印度板块向亚洲板块俯冲的构造效应同样影响到天山地区,使这一晚古生代形成的造山带重新复活。天山南北两侧的晚第三纪和第四纪时期的地层正是对印度板块-亚洲板块碰撞带的响应,发生构造变形,形成了一系列逆冲断层和褶皱,指示这一区域的地壳在晚新生代变短和加厚。文章对天山北缘晚中新世以来的沉积进行了详细的磁性地层学和沉积学研究,结果表明:在研究的独山子背斜地区,磨拉石沉积最早出现于约7百万年前,说明天山山脉自7百万年前开始有一次构造隆升,研究区内7.00~2.58Ma间的巨厚砾石沉积主要是构造抬升的结果。而早更新世的西域砾岩沉积在很大程度上与第四纪时期全球冰期的来临,特别是北半球开始发育大规模冰川作用有关,因此西域砾岩应当是在第四纪冰川作用(气候变冷)及新构造运动共同作用下的产物。     

循化-化隆盆地晚白垩世以来盆山耦合过程: 来自物源与磷灰石裂变径迹年代学分析的证据

循化-化隆盆地新生代沉积及盆地基底和周缘山系磷灰石裂变径迹年代学分析揭示了青藏高原东北缘晚白垩世以来经历过3期隆升剥露事件: (1)盆地基底及拉脊山和西秦岭北缘构造带磷灰石裂变径迹年龄分析普遍记录了晚白垩世-始新世中期相对快速的区域性的隆升剥露事件, 西秦岭北缘快速抬升的起始时间为84Ma, 受控于向北的逆冲抬升; 向北到循化-化隆盆地中部的拉目峡抬升的起始时间为69Ma; 更北的拉脊山一带快速抬升期主要为40~50Ma, 从而反映晚白垩世-始新世中期的快速抬升由南向北逐渐扩展.这一期构造隆升事件导致循化-化隆盆地和临夏盆地缺失了北部西宁-民和盆地古近纪所具有的西宁群沉积.隆升剥露结束于31Ma左右, 此时化隆-循化盆地向东与同时期的临夏盆地相连为一个统一的大型西秦岭山前盆地, 两者具有相同的构造、沉积演化史, 因此循化-化隆盆地他拉组底部地层年龄最老不会超过临夏盆地最老地层的古地磁年龄, 即29Ma.(2)渐新世晚期约26Ma拉脊山开始双向逆冲隆升, 并可能延续到中新世早期约21Ma, 隆升作用使循化-化隆盆地成为挟持于拉脊山逆冲带和西秦岭构造带之间的山前挤压型前陆盆地, 循化-化隆盆地开始大规模沉积巨厚的他拉组冲积扇相粗碎屑岩.(3)通过循化-化隆盆地咸水河组和临夏组的沉积相分析、古流方向和砾石成分分析, 揭示出拉脊山构造带在中新世8Ma左右发生的最大规模的双向逆冲隆升事件, 这次事件直接导致循化-化隆盆地由前陆挤压盆地转变为山间盆地, 形成现今青藏高原东北缘的盆山地貌基本格局.      

The null hypothesis: globally steady rates of erosion,weathering fluxes and shelf sediment accumulation during Late Cenozoic mountain uplift and glaciation

At the largest time and space scales, the pace of erosion and chemical weathering is determined by tectonic uplift rates. Deviations from equilibrium arise from the transient response of landscape denudation to climatic and tectonic perturbations. We posit that the constraint of mass balance, however, makes it unlikely that such disequilibrium persists at the global scale over millions of years, as has been proposed for late Cenozoic erosion. We synthesize weathering fluxes, global sedimentation rates, sediment yields and tectonic motions to show a remarkable constancy in the pace of Earth‐surface evolution over the last 10 Ma and support the null hypothesis – that global rates of landscape change have remained constant over this time period, despite global climate change and mountain building events. This work undermines the hypothesis that increased weathering due to mountain building or climate change was the primary agent for a decrease in global temperatures.     

胶东西北部金矿剥蚀程度及找矿潜力和方向——来自磷灰石裂变径迹热年代学的证据

矿床形成后会经历不同形式的变化,区域隆升与剥蚀是影响矿床变化保存最为关键的因素之一。构造-热年代学是目前广泛运用于研究区域隆升剥蚀的一种重要手段,本文以我国最大金矿集中区———胶东西北部金矿及赋矿围岩玲珑花岗岩为研究对象,尝试将构造-热年代学引用到矿床成矿后变化与保存研究。通过磷灰石裂变径迹热年代学测试获得玲珑花岗岩距今110Ma以来的隆升演化历史,结果显示岩体剥蚀速率很小,平均0.0303±0.0044mm.a-1,自金矿形成后区域热-构造运动趋于平静,这对矿床的保存非常有利。胶东金矿成矿深度范围集中于4~10km,根据剥蚀速度计算玲珑花岗岩剥蚀量仅为2.0~4.2km,远未达到金矿最大成矿深度。当前本区金矿勘探和开采深度普遍小于2km,深部金矿找矿潜力良好。     

云南格咱岛弧印支期地壳隆升与剥蚀及其地质意义:来自黑云母矿物压力计的证据

区域的隆升与剥蚀是影响成矿岩体形成后变化与保存的主要因素,矿物压力计能定量获取花岗质岩浆初始结晶时的压力条件,是研究花岗岩体形成深度及隆升剥蚀历史的有效手段之一。应用黑云母的TAl地质压力计,计算了云南格咱岛弧岩浆岩带印支期典型成矿斑岩体侵位的深度,并估算了格咱岛弧地区地壳的隆升与剥蚀速率,探讨了矿床形成后变化及保存的情况,结果表明印支期以来格咱岛弧地区的成矿岩体剥蚀速率较小,平均为0.018 mm/a,这对矿床形成后的保存较为有利。研究结果为探讨滇西高原印支期以来的构造隆升—剥蚀提供了定量参考。     

地表剥蚀、下地壳流变与造山作用研究进展

岩石圈的流变特性研究已经成为固体地球科学研究中的重要领域,是地球科学新理论、新观点的重要渊源。最近的研究表明,下地壳普遍存在的韧性流是造山作用的重要制约因素。在下地壳物质层流变作用机制的调节下,地表剥蚀作用并不仅仅是传统意义上地表夷平的因素,它还能打破地壳动力学和热力学平衡,引起地壳内物质和结构的重置,进而促成山脉的加剧隆升;地表剥蚀作用的强度既受控于造山带的抬升,也受制于地球外圈层(大气圈、水圈、生物圈)。以天山山脉和喜马拉雅山山脉的隆起、喜马拉雅山山脉的变质作用以及相关的构造活动为例,说明在造山过程中,尽管传统意义上的造山作用与地球内部动力过程,即构造作用有密切联系,但是与构造运动的时空尺度不同,地表剥蚀作用也能够在相对较小的时空尺度内,通过影响和控制造山带下地壳的韧性流动,成为地壳抬升和造山带构造演化的重要动力因素。对地壳的流变特性和变质变形研究是当前地球系统科学研究的一个重要切入点。     

Late Neogene Mountain Building of Eastern Kunlun Orogen: Constrained by DEM Analysis

Topography, as a net result of the dynamic interaction between endogenesis and exogenesis, holds immense information on tectonic uplift, surface erosion and thus mountain building. The eastern Kunlun (昆仑) orogen, which experienced significant Late Neogene tectonic uplift and is located in an arid environment, is advantageous for morphotectonlc analysis based on well-preserved tectonic landforms. The digital elevation model (DEM) analysis was carried out for the central segment of the eastern Kunlun orogen based on shuttle radar topography mission (SRTM) data. River longitudinal profile analysis indicates that major rivers across the orogen are characterized by high river gradient indexes and intensive tectonic uplift. Differential uplift was also identified in swath-topography analysis in the studied area, which can be divided into three major tectonic-geomorphic units by orogenicstrike-parallel faults. It is indicated that the most active region is located to the south of the Xidatan (西大滩) fault with significant differential uplift. Another identified fault with differential uplift is the Middle Kuninn fault; however, the timing of which is suggested to be much older than that of the Xidatan fault. These analyses are eoneordantly supported by both field survey and studies of thermochronology, which in turn indicates that the DEM analysis bears great potential in morphotectonic analysis.