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1.
Regional architecture of geochronology and differential cooling pattern show that the Dabie orogen underwent a thermal doming extension during 140–85 Ma. This extension resulted in widespread re-melting of the Dabie basement, intense volcanic activities in North Huaiyang and the formation of fault-controlled depressions in the Hefei basin. This thermal doming extension can be further divided into two consecutive evolving stages, i.e. the intensifying stage (140–105 Ma) and the declining stage (105–85 Ma). In the first stage (140–105 Ma), the thermal doming mainly was concentrated in the Dabie block, and to a less degree, in the Hongan block. The thermal doming structure of the Dabie block is configured with Macheng-Yuexi thermal axis, Yuexi/Luotian thermal cores and their downslide flanks. The orientation of thermal axis is dominantly parallel to the strike of orogen, and UHP/HP units together with metamorphic rocks of North Huaiyang constitute the downslide flanks. The Yuexi core differs from the Luotian core in both the intensity and the shaping time. To some extent, the Hongan block can be regarded as part of downslide systems of the Dabie doming structure. The doming process is characterized by thermal-center’s migration along the Macheng-Yuexi thermal axis; consequently, it is speculated to be attributed to the convective removal of thickened orogenic root, which is a process characterized by intermittance, mi gration, large-scale and differentiation. During the declining stage (105–85 Ma), the dome-shaped figure still structurally existed in the Dabie orogen, but orogenic units cooled remarkably slow and magmatic activities stagnated gradually. Study on the thermal doming of Dabieshan Mountains can thus provide detailed constraints on the major tectonic problems such as the UHP/HP exhumation model, the boundary between North Dabie and South Dabie, and the orogenesis mechanism.  相似文献   

2.
Thermal histories of Cretaceous sedimentary basins in the Korean peninsula have been assessed to understand the response of the East Asian continental margin to subduction of the Paleo‐Pacific (Izanagi) Plate. The Izanagi Plate subducted obliquely beneath the East Asian continent during the Early Cretaceous and orthogonally in the Late Cretaceous. First, the Jinan Basin, a pull‐apart basin, was studied by illite crystallinity and apatite fission‐track analyses. Analytical results indicate that Jinan Basin sediment was heated to a maximum temperature of approximately 287°C by burial. The sediment experienced two cooling episodes during ca 95–80 Ma and after ca 30 Ma, with a quiescent period between them. A similar cooling pattern is recognized in the Gyeongsang Basin, the largest Cretaceous basin in Korea. The Jinan and Gyeongsang Basins were cooled mainly by exhumation between ca 95 and 80 Ma, but the former was exhumed slightly earlier than the latter by transpressional force due to the subduction direction change of the Izanagi Plate. Comparison of thermal history of Korean Cretaceous basins with those of granitoids in northeastern China and the accretionary complexes in southwestern Japan reveals that the Upper Cretaceous regional exhumation of the East Asian continental margin including the Korean peninsula during ca 95–80 Ma was facilitated by the subduction of the Izanagi–Pacific ridge, which migrated northeastwards with time, resulting in the end of regional exhumation at ca 80 Ma in this region.  相似文献   

3.
Xiaoming  Li  Guilun  Gong  Xiaoyong  Yang  Qiaosong  Zeng 《Island Arc》2010,19(1):120-133
The Yanji area, located at the border of China, Russia, and Korea, where the Phanerozoic granitoids have been widely exposed, was considered part of the orogenic collage between the North China Block in the south and the Jiamusi–Khanka Massifs in the northeast. In this study, the cooling and inferred uplift and denudation history since the late Mesozoic are intensively studied by carrying out apatite and zircon fission-track analyses, together with electron microprobe analyses (EMPA) of chemical compositions of apatite from the granitoid samples in the Yanji area. The results show that: (i) zircon and apatite fission-track ages range 91.7–99.6 Ma and 76.5–85.4 Ma, respectively; (ii) all apatite fission-track length distributions are unimodal and yield mean lengths of 12–13.2 µm, and the apatites are attributed to chlorine-bearing fluorapatite as revealed by EMPA results; and (iii) the thermal history modeling results based on apatite fission-track grain ages and length distributions indicate that the time–temperature paths display similar patterns and the cooling has been accelerated for each sample since ca 15 Ma. Thus, we conclude that sequential cooling, involving two rapid (95–80 Ma and ca 15–0 Ma) and one slow (80–15 Ma) cooling, has taken place through the exhumation of the Yanji area since the late Cretaceous. The maximum exhumation is more than 5 km under a steady-state geothermal gradient of 35°C/km. Combined with the tectonic setting, this exhumation is possibly related to the subduction of the Pacific Plate beneath the Eurasian Plate since the late Cretaceous.  相似文献   

4.
The uplift and exhumation process in the Tianshan orogen since the late Paleozoic were likely related to the preservation of ore deposits. This study involved reconstructing the whole tectonic thermal history of the Ouxidaban pluton in central South Tianshan Mountains based on hornblende/plagioclase Ar-Ar and zircon/apatite(U-Th)/He methods. The thermal history and uplift process of central South Tianshan Mountains since the late Paleozoic were analyzed according to the results of previous works and cooling/exhumation rate features. The hornblende yields a plateau age of 382.6±3.6 Ma, and the plagioclase yields a weighted mean age of 265.8±4.9 Ma. The Ouxidaban pluton yields weighted mean zircon(U-Th)/He age of 185.8±4.3 Ma and apatite(U-Th)/He age of 31.1±2.9 Ma, respectively. Five stages of tectonic thermal history of South Tianshan Mountains since the late Paleozoic could be discriminated by the cooling curve and modeling simulation:(1) from the latest Silurian to Late Devonian, the average cooling rate of the Ouxidaban pluton was 7.84°C/Ma;(2) from the Late Devonian to the latest Middle Permian, the average cooling rate was about 2.07°C/Ma;(3) from the latest Middle Permian to the middle Eocene, the cooling rate decreased to about 0.68°C/Ma, suggesting that the tectonic activity was gentle at this time;(4) a sudden increase of the cooling rate(5.00°C/Ma) and the exhumation rate(0.17 mm/a), and crustal exhumation of ~1.83 km indicated that the Ouxidaban pluton would suffer a rapid uplift event during the Eocene(~46?35 Ma);(5) since the middle Eocene, the rapid uplift was sustained, and the average cooling rate since then has been 1.14°C/Ma with an exhumation rate of about 0.04 mm/a and an exhumation thickness of 1.33 km. The strong uplift since the Cenozoic would be related to a far-field effect from the Indian and Eurasian plates' collision. However, it was hysteretic that the remote effect was observed in the Tianshan orogenic belt.  相似文献   

5.
Exhumation (defined as rock uplift minus surface uplift) in the Cooper Basin of South Australia and Queensland has been quantified using the compaction methodology. The sonic log, which is strongly controlled by the amount of porosity, is an appropriate indicator of compaction, and hence is used for quantifying exhumation from compaction. The traditional way of estimating exhumation based on the degree of overcompaction of a single shale unit has been modified and five units ranging in age from Permian to Triassic have been analysed. The results reveal that exhumation increases eastwards from the South Australia into the Queensland sector of the basin. The results show that exhumation in Late Triassic – Early Jurassic times, after the Cooper Basin deposition, seems to be 200–400 m higher than exhumation in Late Cretaceous – Tertiary times, after the Eromanga Basin deposition. This study has major implications for hydrocarbon exploration. Maturation of source rocks will be greater for any given geothermal history if exhumation is incorporated in maturation modelling. Exhumation values can also be used to improve porosity predictions of reservoir units in undrilled targets.  相似文献   

6.
A model involving buoyancy, wedging and thermal doming is postulated to explain the differential exhumation of ultrahigh-pressure (UHP) metamorphic rocks in the Dabie Mountains, China, with an emphasis on the exhumation of the UHP rocks from the base of the crust to the upper crust by opposite wedging of the North China Block (NCB). The Yangtze Block was subducted northward under the NCB and Northern Dabie microblock, forming UHP metamorphic rocks in the Triassic (240–220 Ma). After delamination of the subduction wedge, the UHP rocks were exhumed rapidly to the base of the crust by buoyancy (220–200 Ma). Subsequently, when the left-lateral Tan–Lu transform fault began to be activated, continuous north–south compression and uplifting of the orogen forced the NCB to be subducted southward under the Dabie Orogen (`opposite subduction'). Opposite subduction and wedging of the North China continental crust is responsible for the rapid exhumation of the UHP and South Dabie Block units during the Early Jurassic, at ca 200–180 Ma at a rate of ∼ 3.0 mm/year. The UHP eclogite suffered retrograde metamorphism to greenschist facies. Rapid exhumation of the North Dabie Block (NDB) occurred during 135–120 Ma because of thermal doming and granitoid formation during extension of continental margin of the Eurasia. Amphibolite facies rocks from NDB suffered retrograde metamorphism to greenschist facies. Different unit(s) and terrane(s) were welded together by granites and the wedging ceased. Since 120–110 Ma, slow uplift of the entire Dabie terrane is caused by gravitational equilibrium.  相似文献   

7.
合肥盆地构造热演化的裂变径迹证据   总被引:12,自引:0,他引:12       下载免费PDF全文
运用裂变径迹分析方法,探讨分析了合肥盆地中新生代的构造热演化特征. 上白垩统和古近系下段样品的磷灰石裂变径迹(AFT)数据主体表现为靠近部分退火带顶部温度(±65℃)有轻度退火,由此估算晚白垩世至古近纪早期合肥盆地断陷阶段的古地温梯度接近38℃/km,高于盆地现今地温梯度(275℃/km).下白垩统、侏罗系及二叠系样品的AFT年龄(975~25Ma)和锆石裂变径迹(ZFT)年龄(118~104Ma)均明显小于其相应的地层年龄,AFT年龄-深度分布呈现冷却型曲线形态,且由古部分退火带、冷却带或前完全退火带及其深部的今部分退火带组成,指示早白垩世的一次构造热事件和其随后的抬升冷却过程. 基于AFT曲线的温度分带模式和流体包裹体测温数据的综合约束,推算合肥盆地早白垩世走滑压陷阶段的古地温梯度接近67℃/km. 径迹年龄分布、AFT曲线拐点年龄和区域抬升剥蚀时间的对比分析结果表明,合肥盆地在早白垩世构造热事件之后的104Ma以来总体处于抬升冷却过程,后期快速抬升冷却事件主要发生在±55Ma.  相似文献   

8.
Noriko  Hasebe  Hiroaki  Watanabe 《Island Arc》2004,13(4):533-543
Abstract   To determine how local geological events contributed to the evolution of accretionary complexes and eventual exposure of rocks with different structural levels, geochronological mapping was carried out using fission track (FT) analysis at the Kii Peninsula, southwest Japan. At this site, the original zonal structure of Cretaceous accretionary complexes parallel to the subduction zone is disturbed by the northward projection of the Shimanto accretionary complex. Twenty-six zircon FT ages were obtained from an area of ∼12 km in an east–west direction and ∼15 km in a north–south direction, and classified into three groups: (i) ages ∼15 Ma (range ∼10–20 Ma), which are distributed along the northwest–southeast valley; (ii) ages of ∼50 Ma in the northwest of the study area; and (iii) ages older than those in Groups 1 and 2. Based on results from eight zircon FT length distributions, the Miocene ages appear to be the result of spatial variations in heat influx and cooling after the regional exhumation of the area, as recorded by FT ages of ∼50 Ma.  相似文献   

9.
江南隆起位于扬子与华夏地块的碰撞汇聚带,是研究华南大地构造演化的关键地质单元.本文采用磷灰石裂变径迹及(U-Th-Sm)/He年龄分布特征定性分析与径迹长度分布数据定量模拟相结合,主要研究了幕阜山岩体新生代的隆升与剥蚀过程,并在此基础上结合区域构造背景, 对其构造-热演化之间的关系进行了探讨.自晚白垩世持续隆升以来,幕阜山岩体经历的平均剥蚀厚度约4800 m.在不同岩体间,隆升过程及幅度存在差异,空间上具有非均匀性.热史结果显示幕阜山岩体经历了3期剥蚀, 其中两期快速剥蚀分别发生在晚白垩世-古近纪(80~50 Ma)和10 Ma以来,而这之间为一期缓慢剥蚀过程.研究区古近纪的快速剥蚀反映了中-下扬子喜山期大规模伸展断陷作用造成的肩部块体快速剥蚀事件; 约10 Ma以来的快速剥蚀是对太平洋板块向西运动的响应.幕阜山岩体自燕山晚期以来的隆升剥蚀作用具有良好的盆地沉积响应, 三期隆升剥蚀事件与研究区构造演化的动力学背景相吻合.  相似文献   

10.
The Helan Mountain lies in the northwest margin of Ordos Basin and its uplift periods have close relations with the tectonic feature and evolution of the basin. There are many views on the uplift time of Helan Mountain, which is Late Triassic and Late Jurassic. It is concluded by the present strata, magmatic rock and hot fluid distribution that the Helan Mountain does not uplift in Late Triassic to Middle Jurassic but after Middle Jurassic. Through the research of the sedimentary strata and deposit rate in Yinchuan Graben which is near to the Helan Mountain, it is proved that the Helan Mountain uplifts in Eocene with a huge scale and in Pliocene with a rapid speed. The fission track analysis of apatite and zircon can be used to determine the precise uplift time of Helan Mountain, which shows that four stages of uplifting or cooling Late Jurassic to the early stage of Early Cretaceous, mid-late stage of Early Cretaceous, Late Cretaceous and since Eocene. During the later two stages the uplift is most apparent and the mid-late stage of Early Cretaceous is a regional cooling course. Together with several analysis ways, it is considered that the earliest time of Helan Mountain uplift is Late Jurassic with a limited scale and that Late Cretaceous uplift is corresponding to the whole uplift of Ordos Basin, extensive uplift happened in Eocene and rapid uplift in Pliocene.  相似文献   

11.
Paleontological and stratigraphical data indicate that a link between terminal southern South America and the Antarctic Peninsula probably was an irregularly narrow continuous land from Late Cretaceous (Campanian) through the Eocene period. In paleogeographical feature it is more like modern Isthmus of Panama. A paleoisthmus called the isthmus of Scotia is hypothesized as a type of connection between them. It lasted about 35 Ma and extended about 700–900 km long and 100–200 krn wide. This isthmus played an important role in biotic dispersal and migra-tion among South America, Antarctica, Australia and New Zealand blocks during this interval. Project supported by the Science and Technology Con~rnission, the Chinese Academy of Sciences and the National Natural Science Foundation of China (Grant No. 49572076).  相似文献   

12.
The Helan Mountain lies in the northwest margin of Ordos Basin and its uplift periods have close relations with the tectonic feature and evolution of the basin. There are many views on the uplift time of Helan Mountain, which is Late Triassic and Late Jurassic. It is concluded by the present strata, magmatic rock and hot fluid distribution that the Helan Mountain does not uplift in Late Triassic to Middle Jurassic but after Middle Jurassic. Through the research of the sedimentary strata and deposit rate in Yinchuan Graben which is near to the Helan Mountain, it is proved that the Helan Mountain uplifts in Eocene with a huge scale and in Pliocene with a rapid speed. The fission track analysis of apatite and zircon can be used to determine the precise uplift time of Helan Mountain, which shows that four stages of uplifting or cooling: Late Jurassic to the early stage of Early Cretaceous, mid-late stage of Early Cretaceous, Late Cretaceous and since Eocene. During the later two stages the uplift is most apparent and the mid-late stage of Early Cretaceous is a regional cooling course. Together with several analysis ways, it is considered that the earliest time of Helan Mountain uplift is Late Jurassic with a limited scale and that Late Cretaceous uplift is corresponding to the whole uplift of Ordos Basin, extensive uplift happened in Eocene and rapid uplift in Pliocene.  相似文献   

13.
报道了米仓山-汉南穹窿一带磷灰石裂变径迹分析结果,以制约该区白垩纪以来的剥蚀-演化历史.露头样品磷灰石裂变径迹年龄分布显示从汉南穹窿南部的核部地区向南至四川盆地北部裂变径迹的年龄逐渐变新,这与米仓山地区逆冲断裂以背驮式扩展的构造样式从汉南穹窿向南经米仓山褶皱-逆冲带发育到四川盆地北缘的构造模式相吻合.热模拟的结果显示米仓山-汉南穹窿经历了两期快速的剥蚀,其分别发生在白垩纪(约90 Ma之前)和15 Ma以来.研究区白垩纪的快速剥蚀反映了秦岭-大别造山带白垩纪的区域性剥蚀事件,这可能是对临区诸多构造事件(如西伯利亚-蒙古-中朝板块的碰撞,拉萨-羌塘-思茅-印支块体的碰撞,太平洋板块向欧亚板块的俯冲及其相关的岩浆活动)远场效应的响应;约15 Ma以来的快速剥蚀是对青藏高原隆升向东北方向传递的响应.  相似文献   

14.
五台山新生代隆升剥露的磷灰石裂变径迹研究   总被引:5,自引:1,他引:4       下载免费PDF全文
五台山是中国三级地貌重要分界线之一太行山脉海拔最高的山,其隆升历史的研究对中国三级地貌形成时代的确定具有重要意义.沿五台山最高峰北台顶向北自上而下至山根和阜平县境内长城岭地区海拔最高点向东自上而下至山根两条剖面,分别采集一系列岩石样品,最后挑选16个样品进行磷灰石裂变径迹研究.通过对封闭径迹长度分布直方图的分析,表明五台山样品自晚白垩纪末以来一直在单调冷却,即五台山在持续地隆升;通过对样品径迹年龄-高程图的分析,同时结合热史模拟及Excel数据拟合,表明晚白垩纪末以来五台山的隆升为分阶段幕式过程,共经历了三期快速隆升:74~58 Ma、46~31 Ma及15 Ma左右.五台山晚白垩纪末以来的隆升与太行山其他地区及周边张宣隆起、泰山等其他山系的隆升在时间上存在对应关系,所以,五台山新生代隆升为区域性构造演化的一部分.  相似文献   

15.
对米仓山南江-南郑剖面上的13个花岗岩类样品进行了磷灰石(U-Th)/He测年和剥露速率计算,分析过程综合考虑了样品冷却速率、晶体大小等因素对磷灰石(U-Th)/He封闭温度的影响和地形起伏、岩体热传导、热对流及放射性元素生热等因素对地温场的影响.研究表明,米仓山南部沉积变形区自~50 Ma以来发生快速剥露 (剥露速率为~70 m/Ma),新生代以来的剥蚀量超过了3 km;中部光雾山杂岩体记录了~90 Ma时一次快速剥露事件(剥露速率>75 m/Ma);北部汉南隆起区~100 Ma以前以快速剥露为特点,平均剥露速率>40 m/Ma,此后转为缓慢剥露.整个米仓山-汉南隆起区在90~50 Ma基本处于缓慢剥露状态,平均剥露速率仅有10~25 m/Ma.  相似文献   

16.
The thermochronology based on a combination ofradiometric age and closure temperature (Tc) is widelyaccepted as a sensitive method to provide constraintson tectonic evolution of the orogen, and numerousadvances as a result of thermochronological applica-tions have been made recently in the Dabieshan oro-gen[1—5]. Zircon U/Pb, hornblende Ar/Ar and biotiteAr/Ar ages with Tc= 800—300℃[6] will yield a wealthof information on the cooling and exhumation of rockscrossing crustal levels of 30—1…  相似文献   

17.
Regional architecture of geochronology and differential cooling pattern show that the Dabie orogen underwent a thermal doming extension during 140-85 Ma. This extension resulted in widespread re-melting of the Dabie basement, intense volcanic activities in North Huaiyang and the formation of fault-controlled depressions in the Hefei basin. This thermal doming extension can be further divided into two consecutive evolving stages, i.e. the intensifying stage (140-105 Ma) and the declining stage (105-85 Ma). In the first stage (140-105 Ma), the thermal doming mainly was concentrated in the Dabie block, and to a less degree, in the Hongan block. The thermal doming structure of the Dabie block is configured with Macheng-Yuexi thermal axis, Yuexi/Luotian thermal cores and their downslide flanks. The orientation of thermal axis is dominantly parallel to the strike of orogen, and UHP/HP units together with metamorphic rocks of North Huaiyang constitute the downslide flanks. The Yuexi core differs from the Luotian core in both the intensity and the shaping time. To some extent, the Hongan block can be regarded as part of downslide systems of the Dabie doming structure. The doming process is characterized by thermal-center's migration along the Macheng-Yuexi thermal axis; consequently, it is speculated to be attributed to the convective removal of thickened orogenic root, which is a process characterized by intermittance, migration, large-scale and differentiation. During the declining stage (105-85 Ma), the dome- shaped figure still structurally existed in the Dabie orogen, but orogenic units cooled remarkably slow and magmatic activities stagnated gradually. Study on the thermal doming of Dabieshan Mountains can thus provide detailed constraints on the major tectonic problems such as the UHP/HP exhumation model, the boundary between North Dabie and South Dabie, and the orogenesis mechanism.  相似文献   

18.
The mineralization ages reported in the past in the Tuwu-Yandong copper district not only are different,but also fall into the Hercynian epoch.This study has achieved 9 zircon and 7 apatite fission track analysis results.The zircon fission track ages range from 158 Ma to 289 Ma and the apatite ages are between 64 Ma and 140 Ma.The mineralization accords with the regional tectonics in the copper district.We consider that the zircon fission track age could reveal the mineralization age based on annealing zone temperature of 140―300℃ and retention temperature of ~250℃ for zircon fission track,and metallogenetic temperature of 120―350℃ in this ore district.Total three mineralization epochs have been identified,i.e.,289―276 Ma,232―200 Ma and 165―158 Ma,and indicate occurrence of the min-eralization in the Indosinian and Yanshan epochs.Corresponding to apatite fission track ages,the three tectonic-mineralizing epochs are 140―132 Ma,109―97 Ma and 64 Ma,which means age at about 100℃ after the mineralization.The three epochs lasted 146 Ma,108 Ma and about 100 Ma from ~250℃ to ~100℃ and trend decrease from early to late.It is shown by the fission track modeling that this district underwent three stages of geological thermal histories,stable in Cretaceous and cooling both before Cretaceous and after 20 Ma.  相似文献   

19.
The Cretaceous Toki granitic pluton of the Tono district, central Japan was emplaced in the East Asian continental margin at about 70 Ma. The Toki granite has apatite fission‐track (AFT) ages ranging from 52.1 ±2.8 Ma to 37.1 ±3.6 Ma (number of measurements, n = 33); this indicates the three‐dimensional thermal evolution during the pluton's low‐temperature history (temperature in the AFT partial annealing zone: 60–120 °C). The majority of the Toki granite has a spatial distribution of older ages in the shallower parts and younger ages in the deeper parts, representing that the shallower regions arrived (were exhumed) at the AFT closure depth earlier than the deeper regions. Such a cooling pattern was predominantly constrained by the exhumation of the Toki granitic pluton and was related to the regional denudation of the Tono district. The age–elevation relationships (AERs) of the Toki granite indicate a fast exhumation rate of about 0.16 ±0.04 mm/year between 50 Ma and 40 Ma. The AFT inverse calculation using HeFTy program gives time‐temperature paths (tT paths), suggesting that the pluton experienced continuous slow cooling without massive reheating since about 40 Ma until the present day. A combination of the AERs and AFT inverse calculations represents the following exhumation history of the Toki granite: (i) the fast exhumation at a rate of 0.16 ±0.04 mm/year between 50 Ma and 40 Ma; (ii) slow exhumation at less than 0.16 ±0.04 mm/year after 40 Ma; and (iii) exposure at the surface prior to 30–20 Ma. The Tono district, which contains the Toki granite, underwent slow denudation at a rate of less than 0.16 ±0.04 mm/year within the East Asian continental margin before the Japan Sea opening at 25–15 Ma and then within the Southwest Japan Arc after the Japan Sea opening, which is in good agreement with representative denudation rates obtained in low‐relief hill and plain fields.  相似文献   

20.
For the Triassic continental collision, subduction and orogenesis in the Dabie-Sulu belt, a lot of data on petrology, geochemistry and chronology have been published[1]. However, so far no depositional records on the Triassic syn-collisional orogenesis of…  相似文献   

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