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1.
<正>The Liiliang Mountains,located in the North China Craton,is a relatively stable block,but it has experienced uplift and denudation since the late Mesozoic.We hence aim to explore its time and rate of the exhumation by the fission-track method.The results show that,no matter what type rocks are,the pooled ages of zircon and apatite fission-track range from 60.0 to 93.7 Ma and 28.6 to 43.3 Ma,respectively;all of the apatite fission-track length distributions are unimodal and yield a mean length of～13μm;and the thermal history modeling results based on apatite fission-track data indicate that the time-temperature paths exhibit similar patterns and the cooling has been accelerated for each sample since the Pliocene(c.5 Ma).Therefore,we can conclude that a successive cooling,probably involving two slow(during c.75-35Ma and 35-5Ma) and one rapid(during c.5 Ma-0 Ma) cooling,has occurred through the exhumation of the Liiliang Mountains since the late Cretaceous.The maximum exhumation is more than 5 km under a steady-state geothermal gradient of 35℃/km.Combined with the tectonic setting,this exhumation may be the resultant effect from the surrounding plate interactions,and it has been accelerated since c.5 Ma predominantly due to the India-Eurasia collision.  相似文献   

2.
<正>Does Cenozoic exhumation occur in the Larsemann Hills,East Antarctica? In the present paper,we conducted an apatite fission-track thermochronologic study across the Larsemann Hills of East Antarctica.Our work reveals a Cenozoic exhumation event at 49.8±12 Ma,which we interpret to be a result of exhumation caused by crustal extension.Within the uncertainty of our age determination, the timing of extension in East Antarctica determined by our study is coeval with the onset time of rifting in West Antarctica at c.55 Ma.The apatite fission-track cooling ages vary systematically in space, indicating a coherent block rotation of the Larsemann Hills region from c.50 Ma to c.10 Ma.This pattern of block tilting was locally disrupted by normal faulting along the Larsemann Hills detachment fault at c.5.4 Ma.The regional extension in the Larsemann Hills,East Antarctica was the result of tectonic evolution in this area,and may be related to the global extension.Through the discussion of Pan-Gondwanaland movement,and Mesozoic and Cenozoic extensions in West and East Antarctica and adjacent areas,we suggest that the protracted Cenozoic cooling over the Larsemann Hills area was caused by extensional tectonics related to separation and formation of the India Ocean at the time of Gondwanaland breakup.  相似文献   

3.
Zircon and apatite fission-track dating indicates that the exhumation of the Dabie Mountains tended to be accelerated in the Cenozoic and that the exhumation of the eastern Dabie Mountains was more and more intense from south to north, which is in accordance with the more and more intense dissection from south to north, as is reflected by the modern geomorphologic features of the Dabie Mountains. The accelerated exhumation during the Cenozoic was related to the high elevation of the Dabie Mountains resulting from Late Cretaceous-Palaeogene detachment faulting and subsequent fault-block uplift and subsidence. The average elevation at that time was at least about 660 m higher than that at the present. The intense exhumation lagged behind intense uplift.  相似文献   

4.
Although many authors have emphasized the Cenozoic history of deformation, exhumation and cooling in the Tiaushan area related to the India-Asia collision, very little is known about the Mesozoic history of compression and uplift within the Tianshan. In order to obtain information about the Mesozoic exhumation history and processes of cooling in eastern Tianshan, fission track methods on apatite were used. Sampling was made in the Jueluotage Range. Three samples （Z001-Z003） were taken from granite in borehole ZK6301 of Yandong pluton; the ages range from 97.0 to 87.6 Ma that are much younger than the pluton age which was dated by U-Pb zircon at 334±2 Ma. Two samples in northern piedmont of the Jueluotage Range were collected from Jurassic strata in Dikaner （DK001） and Dananhu （D001） whose ages are 91.5 and 93.4 Ma respectively. The average apparent exhumation rate is 0.039 nun/a calculated by extrapolation on the basis of Yandong samples, indicating an extremely slow exhumation in the Jueluotage Range since the Late Cretaceous. Two Jurassic samples reached the maximum depths after deposition and experienced the maximum temperatures of ca. 105 and 108℃ until the late Early Cretaceous before a period of cooling and exhumation occurred at 114 and 106 Ma.  相似文献   

5.
The Mesozoic–Cenozoic uplift history of South Tianshan has been reconstructed in many ways using thermochronological analyses for the rocks from the eastern Kuqa Depression. The main difference in the reconstructions concerns the existence and importance of Early Cretaceous and Paleogene tectonic activities, but the existence of a Cenozoic differential uplift in the Kuqa Depression remains enigmatic. Here, we present new apatite fission-track ages obtained for 12 sandstone samples from the well-exposed Early Triassic to Quaternary sequence of the Kapushaliang section in the western Kuqa Depression. The results reveal that there were four pulses of tectonic exhumation, which occurred during the Early Cretaceous(peak ages of 112 and 105 Ma), Late Cretaceous(peak age of 67 Ma), Paleocene–Eocene(peak ages at 60, 53, and 36 Ma), and early Oligocene to late Miocene(central ages spanning 30–11 Ma and peak ages of 23 and 14 Ma), respectively. A review of geochronological and geological evidence from both the western and eastern Kuqa Depression is shown as follows.(1) The major exhumation of South Tians Shan during the Early Cretaceous was possibly associated with docking of the Lhasa block with the southern margin of the Eurasian plate.(2) The Late Cretaceous uplift of the range occurred diachronically due to the far-field effects of the Kohistan-Dras Arc and Lhasa block accretion.(3) The Paleogene uplift in South Tianshan initially corresponded to the far-field effects of the India–Eurasia collision.(4) The rapid exhumation in late Cenozoic was driven by the continuous far-field effects of the collision between India and Eurasia plates. The apatite fission-track ages of 14–11 Ma suggest that late Cenozoic exhumation in the western Kuqa Depression prevailed during the middle to late Miocene, markedly later than the late Oligocene to early Miocene activity in the eastern segment. It can be hypothesized that a possible differential uplift in time occurred in the Kuqa Depression during the late Cenozoic.  相似文献   

6.
The Qiangtang basin is located in the central Tibetan Plateau. This basin has an important structural position,and further study of its tectonic and thermal histories has great significance for understanding the evolution of the Tibetan Plateau and the hydrocarbon potential of marine carbonates in the basin. This study focuses on low temperature thermochronology and in particular conducted apatite fission track analysis. Under constraints provided by the geological background,the thermal history in different tectonic units is characterized by the degree of annealing of samples,and the timing of major(uplift-erosion related) cooling episodes is inferred. The cooling history in the Qiangtang basin can be divided into two distinct episodes. The first stage is mainly from the late Early Cretaceous to the Late Cretaceous(69.8 Ma to 108.7 Ma),while the second is mainly from the MiddleLate Eocene to the late Miocene(10.3 Ma to 44.4 Ma). The first cooling episode records the uplift of strata in the central Qiangtang basin caused by continued convergent extrusion after the BangongNujiang ocean closed. The second episode can be further divided into three periods,which are respectively 10.3 Ma,22.6–26.1 Ma and 30.8–44.4 Ma. The late Oligocene-early Miocene(22.6–26.1 Ma) is the main cooling period. The distribution and times of the earlier uplift-related cooling show that the effect of extrusion after the collision between Eurasian plate and India plate obviously influenced the Qiangtang basin at 44.4 Ma. The Qiangtang basin underwent compression and started to be uplifted from the middle-late Eocene to the early Oligocene(45.0–30.8 Ma). Subsequently,a large-scale and intensive uplift process occurred during the late Oligocene to early Miocene(26.1–22.6 Ma) and the basin continued to undergo compression and uplift up to the late Miocene(10.3 Ma). Thus,uplift-erosion in the Qiangtang basin was intensive from 44.5 Ma to about 10 Ma. The timing of cooling in the second episode shows that the uplift of the Qiangtang basin was caused by the strong compression after the collision of the Indian plate and Eurasian plate. On the whole,the new apatite fission-track data from the Qiangtang basin show that the Tibetan Plateau started to extrude and uplift during 45–30.8 Ma. The main period of uplift and formation of the Tibetan Plateau took place about 22.6–26.1 Ma,and uplift and extrusion continued until the late Miocene(10.3 Ma).  相似文献   

7.
The Cretaceous-Eocene Xigaze forearc basin is a crucial data archive for understanding the tectonic history of the Asian continental margin prior to and following collision with India during the early Cenozoic Era. This study reports apatite and zircon(U-Th)/He thermochronologic data from fourteen samples from Albian-Ypresian Xigaze forearc strata to determine the degree and timing of heating(burial) and subsequent cooling(exhumation) of two localities along the Yarlung suture zone(YSZ) near the towns of Saga and Lazi. Thirty-seven individual zircon He ages range from 31.5 ± 0.8 Ma to6.06 ± 0.18 Ma,with the majority of grains yielding ages between 30 Ma and 10 Ma. Twenty apatite He ages range from 12.7 ± 0.5 Ma to 3.9 ± 0.3 Ma,with the majority of grains yielding ages between 9 Ma and 4 Ma. These ages suggest that the Xigaze forearc basin was heated to 140-200 ℃ prior to cooling in Oligocene-Miocene time. Thermal modeling supports this interpretation and shows that the samples were buried to maximum temperatures of ～140-200 0 C by 35-21 Ma, immediately followed by the onset of exhumation. The zircon He and apatite He dataset and thermal modeling results indicate rapid exhumation from ～21 Ma to 15 Ma, and at ～4 Ma. The 21-15 Ma thermochronometric signal appears to be regionally extensive, affecting all the lithotectonic units of the YSZ, and coincides with movement along the north-vergent Great Counter Thrust system. Thrusting, coupled with enhanced erosion possibly related to the paleo-Yarlung River, likely drove Early Miocene cooling of the Xigaze forearc basin.In contrast, the younger phase of rapid exhumation at ～4 Ma was likely driven by enhanced rock uplift in the footwall of north-striking rifts that cross-cut the YSZ.  相似文献   

8.
Plate subduction leads to complex exhumation processes on continents. The Huangling Massif lies at the northern margin of the South China Block. Whether the Huangling Massif was exhumed as a watershed of the middle reaches of the Paleo-Yangtze River during the Mesozoic remains under debate. We examined the exhumation history of the Huangling Massif based on six granite bedrock samples, using apatite fission track (AFT) and apatite and zircon (U-Th)/He (AHe and ZHe) thermochronology. These samples yielded ages of 157–132 Ma (ZHe), 119–106 Ma (AFT), and 114–72 Ma (AHe), respectively. Thermal modeling revealed that three phases of rapid cooling occurred during the Late Jurassic–Early Cretaceous, late Early Cretaceous, and Late Cretaceous. These exhumation processes led to the high topographic relief responsible for the emergence of the Huangling Massif. The integrated of our new data with published sedimentological records suggests that the Huangling Massif might have been the watershed of the middle reaches of the Paleo-Yangtze River since the Cretaceous. At that time, the rivers flowed westward into the Sichuan Basin and eastward into the Jianghan Basin. The subduction of the Pacific Plate beneath the Asian continent in the Mesozoic deeply influenced the geomorphic evolution of the South China Block.  相似文献   

9.
Xiazhuang uranium ore field, located in the southern part of the Nanling Metallogenic Belt, is considered one of the largest granite-related U regions in South China. In this paper, we contribute new apatite fission track data and thermal history modeling to constrain the exhumation history and evaluate preservation potential of the Xiazhuang Uranium ore field. Nine Triassic outcrop granite samples collected from different locations of Xiazhuang Uranium ore field yield AFT ages ranging from 43 to 24 Ma with similar mean confined fission track lengths ranging from 11.8 ± 2.0 to 12.9 ± 1.9 μm and Dpar values between 1.01 and 1.51 μm. The robustness time-temperature reconstructions of samples from the hanging wall of Huangpi fault show that the Xiazhuang Uranium ore field experienced a time of monotonous and slow cooling starting from middle Paleocene to middle Miocene (~60–10 Ma), followed by relatively rapid exhumation in the late Miocene (~10–5 Ma) and nearly thermal stability in the Pliocene–Quaternary (~5–0 Ma). The amount of exhumation after U mineralization since the Middle Paleogene was estimated as ~4.3 ± 1.8 km according to the integrated thermal history model. Previous studies indicate that the ore-forming ages of U deposits in the Xiazhuang ore field are mainly before Middle Paleocene and the mineralization depths are more than 4.4 ± 1.2 km. Therefore, the exhumation history since middle Paleocene plays important roles in the preservation of the Xiazhuang Uranium ore field.  相似文献   

10.
Diffusion modeling of zoning profiles in eclogite garnets from three different tectonic units of Mt. Dabie, UHPM unit, HPM unit and northern Dabie, was used to estimate the relative time span and cooling rates of these rocks. Modeling result for the Huangzhen eclogite garnet shows that the maximal time span for the diffusion-adjustment process is about 22 Ma since the peak-temperature metamorphism, which is the maximum time span from amphibolite facies metamorphism to greenschist facies metamorphism. The Bixiling eclogites had subjected to a cooling process at a rate of - 10℃/Ma from 750℃ to 560℃ during 20 Ma. The second cooling stage of the Raobazhai eclogite following granulite-facies metamorphism is an initial fast cooling process at a rate of about 25℃/Ma and then slowed down gradually. All these belong to a coherent Dabie collision orogen with differences in subduction depth and exhumation/uplifting path.  相似文献   

11.
The Mesozoic–Cenozoic tectonic movement largely controls the northwest region of the Junggar Basin (NWJB), which is a significant area for the exploration of petroleum and sandstone-type uranium deposits in China. This work collected six samples from this sedimentary basin and surrounding mountains to conduct apatite fission track (AFT) dating, and utilized the dating results for thermochronological modeling to reconstruct the uplift history of the NWJB and its response to hydrocarbon migration and uranium mineralization. The results indicate that a single continuous uplift event has occurred since the Early Cretaceous, showing spatiotemporal variation in the uplift and exhumation patterns throughout the NWJB. Uplift and exhumation initiated in the northwest and then proceeded to the southeast, suggesting that the fault system induced a post spread-thrust nappe into the basin during the Late Yanshanian. Modeling results indicate that the NWJB mountains have undergone three distinct stages of rapid cooling: Early Cretaceous (ca. 140–115 Ma), Late Cretaceous (ca. 80–60 Ma), and Miocene–present (since ca. 20 Ma). These three stages regionally correspond to the Lhasa-Eurasian collision during the Late Jurassic–Early Cretaceous (ca. 140–125 Ma), the Lhasa-Gandise collision during the Late Cretaceous (ca. 80–70 Ma), and a remote response to the India-Asian collision since ca. 55 Ma, respectively. These tectonic events also resulted in several regional unconformities between the J3/K1, K2/E, and E/N, and three large-scale hydrocarbon injection events in the Piedmont Thrust Belt (PTB). Particularly, the hydrocarbon charge event during the Early Cretaceous resulted in the initial inundation and protection of paleo-uranium ore bodies that were formed during the Middle–Late Jurassic. The uplift and denudation of the PTB was extremely slow from 40 Ma onward due to a slight influence from the Himalayan orogeny. However, the uplift of the PTB was faster after the Miocene, which led to re-uplift and exposure at the surface during the Quaternary, resulting in its oxidation and the formation of small uranium ore bodies.  相似文献   

12.
Apatite fission track （AFT） thermochronology of seven samples from the Xiaonanchuan （小南川） pluton in the Kunlun （昆仑） pass area was carried out, for the purpose of determining the timing of cooling and the relation between the exhumation and the morphotectonic processes. The AFT ages yield low denudation rates of 0. 020--0. 035 mm/a during the late Miocene, which correspond to a stable geomorphic and weak tectonic uplifting environment. The low denudation rates can be considered as the approximate tectonic uplifting rates. The AFT geochronology shows puroxysmully rapid cooling since the Pliocene and an apparent material unroofing of more than 3 km in the Xiaonanchuan area. This was not the result of simple denudation. The rapid cooling was coupled with the intensive orogeny since the Pliocene, which was driven by tectonic uplifting. The accelerated relief building was accompanied by a series of faulting, which caused the basin and the valley formation and sinking. The space pattern of the AFT ages also shows differential uplifting, which decreases northwardly. This trend is supported by the regional AFT data, which indicate that the exhumation decreases northwardly in eastern Kunlun. This trend also exists in cast-west orientation from the western Kunlun range to the eastern. The uplif- ting trend is also supported by gcomorphic characteristics including the elevation and the relief differences well as the distribution of the Late Cenozoic volcanism.  相似文献   

13.
The Hengshan complex is located in the central part of SE China, which underwent rapid tectonic uplift in the Cretaceous just like many other complexes on the continent. (40)~Ar–(39)~Ar geochronological data from the Hengshan complex suggest that two episodes of crustal cooling/extension took place in this part of the continent during the Cretaceous time. The first stage of exhumation was active during ca. 136–125 Ma, with a cooling rate of 10 °C/Ma. The second stage of exhumation happened at ca. 98–93 Ma, with a cooling rate of 10 °C/Ma. Considering the folding in the Lower Cretaceous sedimentary rocks and the regional unconformity underneath the Upper Cretaceous red beds, it is believed that the Cretaceous crustal extension in SE China was interrupted by a compressional event. The reversion to extension, shortly after this middle Cretaceous compression, led to the rapid cooling/exhumation of the Hengshan complex at ca. 98–93 Ma. The Cretaceous tectonic processes in the hinterland of SE China could be controlled by interactions between the continental margin and the Paleo–pacific plate.  相似文献   

14.
Five samples of muscovite from mylonites of the earlier Tanlu ductile shear zone on the eastern margin of the Dabie Mountains yield 40Ar/39Ar ages ranging from 178 Ma to 196 Ma. Three of them have reliable plateau ages of 188.7±0.7 Ma, 189.7±0.6 Ma and 192.5±0.7 Ma respectively, which indicates a syn-orogenic, sinistral strike-slip thermal event. This displacement movement derived from the continent-continent collision of the North and South China blocks took place in the Early Jurassic and after uplifting of high-pressure to ultrahigh-pressure slabs to the mid-crust. It is suggested that during the collision the Tanlu fault zone was an intracontinental transform fault caused by differential subduction speeds. The 40Ar/39Ar ages of mylonite whole-rock and muscovite from the later Tanlu ductile shear zone suggest another sinistral strike-slip cooling event at 128 Ma. During this strike-slip faulting, large-scale intrusion and doming uplift occurred in the eastern part of the Dabie orogenic belt. Data o  相似文献   

15.
Geochronology of oil-gas accumulation （OGA） is a challenging subject of petroleum geology in multi-cycle superimposed basins.By K-Ar dating of authigenic illite （AI） and fluid inclusion （FI） analysis combined with apatite fission track （AFT） thermal modeling,a case study of constraining the OGA times of the Permian reservoirs in northeast Ordos basin （NOB） has been conducted in this paper.AI dating of the Permian oil-gas-bearing sandstone core-samples shows a wide time domain of 178-108 Ma.The distribution of the AI ages presents 2-stage primary OGA processes in the Permian reservoirs,which developed in the time domains of 175-155 Ma and 145-115 Ma with 2-peak ages of 165 Ma and 130 Ma,respectively.The FI temperature peaks of the samples and their projected ages on the AFT thermal path not only present two groups with a low and a high peak temperatures in ranges of 90-78℃ and 125-118℃,respectively corresponding to 2-stage primary OGA processes of 162-153 Ma and 140-128 Ma in the Permian reservoirs,but also appear a medium temperature group with the peak of 98℃ in agreement with a secondary OGA process of c.～30 Ma in the Upper Permian reservoirs.The integrated analysis of the AI and FI ages and the tectono-thermal evolution reveals that the Permian reservoirs in the NOB experienced at least 2-stage primary OGA processes of 165-153 Ma and 140-128 Ma in agreement with the subsidence thermal process of the Mid-Early Jurassic and the tectono-thermal event of the Early Cretaceous.Then,the Upper Permian reservoirs further experienced at least 1-stage secondary OGA process of c.～30 Ma in coincidence with a critical tectonic conversion between the slow and the rapid uplift processes from the Late Cretaceous to Neogene.  相似文献   

16.
The Tarim Basin is a representative example of the basins developed in the northwest China that are characterized by multiple stages of heating and cooling.In order to better understand its complex thermal history,apatite fission track （AFT） thermochronology was applied to borehole samples from the Tazhong Uplift Zone （TUZ）.Twelve sedimentary samples of Silurian to Triassic depositional ages were analyzed from depths coinciding with the apatite partial annealing zone （～60-120 ℃）.The AFT ages,ranging from 132 ± 7 Ma （from a Triassic sample） to 25 ± 2 Ma （from a Carboniferous sample）,are clearly younger than their depositional ages and demonstrate a total resetting of the AFT thermometer after deposition.The AFT ages vary among different tectonic belts and decrease from the No.Ten Faulted Zone （133-105 Ma） in the northwest,the Central Horst Zone in the middle （108-37 Ma）,to the East Buried Hill Zone in the south （51 25 Ma）.Given the low magnitude of post-Triassic burial heating evidenced by low vitrinite reflectance values （Ro ＜ 0.7％）,the total resetting of the AFT system is speculated to result from the hot fluid flow along the faults.Thermal effects along the faults are well documented by younger AFT ages and unimodal single grain age distributions in the vicinity of the faults.Permian-early Triassic basaltic volcanism may be responsible for the early Triassic total annealing of those samples lacking connectivity with the fault.The above arguments are supported by thermal modeling results.  相似文献   

17.
http://www.sciencedirect.com/science/article/pii/S1674987115001334   总被引：2，自引：0，他引：2  
The Hongyanjing inter-arc basin,is located at the central part of Beishan Orogenic College(BOC),Gansu Province,northwest China.Thick sequences of Permian sediments were strongly folded,forming extremely spectacular superposed folds.To better understand the thermal history of Hongyanjing interarc basin and to potentially constrain the timing of deformation,apatite fission track thermochronology method was applied on two superposed folds in the Hongyanjing Basin.Samples from the basin,yield central AFT ages ranging from-206 to 118 Ma.AFT peak ages were largely consistent between samples and can divided into three groups:245,204-170 and 112-131 Ma.Subsequent thermal history modeling of the samples from the Hongyanjing Basin can be summarized as follows:(1) thermal reheating by sedimentary burial at ~ 260 to-220 Ma;(2) major cooling from-220 to- 180 Ma;(3) an episode of very slow subsequent cooling from ~180 to 65 Ma(-80 ℃) to present-day outcrop temperatures.Sediments in the Hongyanjing Basin were folded forming F_1 fold during the early to late Triassic(-240-~220 Ma),by regional stress,and at the time that the adjacent Xingxingxia shear zone started to become active.It is further suggested that the F_2 folding occurred at ~225-219 Ma.The deformation age of F_2 should be extended to 180 Ma based on our thermal history modeling for the Hongyanjing Basin,which show a rapid exhumation and cooling at the late Triassic to early Jurassic(-220-~180 Ma).In our interpretations,the F_1 folding is therefore thought to be related to the final closure of the Paleo-Asian Ocean,while the F_2 folding occurred at ~225-180 Ma associated with a major pulse of orogenesis in the BOC.  相似文献   

18.
Determining the spatio-temporal distribution of the deformation tied to the India-Eurasian convergence and the impact of pre-existing weaknesses on the Cenozoic crustal deformation is significant for understanding how the convergence between India and Eurasia contributed to the development of the Tibetan Plateau. The exhumation history of the northeastern Tibetan Plateau was addressed in this research using a new apatite fission track (AFT) study in the North Qaidam thrust belt (NQTB). Three granite samples collected from the Qaidam Shan pluton in the north tied to the Qaidam Shan thrust, with AFT ages clustering in the Eocene to Miocene. The other thirteen samples obtained from the Luliang Shan and Yuka plutons in the south related to the Luliang Shan thrust and they have showed predominantly the Cretaceous AFT ages. Related thermal history modeling based on grain ages and track lengths indicates rapid cooling events during the Eocene-early Oligocene and since late Miocene within the Qaidam Shan, in contrast to those in the Cretaceous and since the Oligocene-Miocene in the Luliang Shan and Yuka region. The results, combined with published the Cretaceous thermochronological ages in the Qaidam Shan region, suggest that the NQTB had undergo rapid exhumation during the accretions along the southern Asian Andean-type margin prior to the India-Eurasian collision. The Cenozoic deformation initially took place in the North Qaidam thrust belt by the Eocene, which is consistent with the recent claim that the deformation of the northeastern Tibetan Plateau initiated in the Eocene as a response to continental collision between India and Eurasia. The immediate deformation responding to the collision is tentatively attributed to the pre-existing weaknesses of the lithosphere, and therefore the deformation of the northeastern Tibetan Plateau should be regarded as a boundary-condition-dependent process.  相似文献   

19.
The apatite fission track (AFT) ages and thermal modeling of the Longshoushan and deformation along the northern Hexi Corridor on the northern side of the Qinghai-Tibetan Plateau show that the Longshoushan along the northern corridor had experienced important multi-stage exhumations during the Late Mesozoic and Cenozoic. The AFT ages of 7 samples range from 31.9 Ma to 111.8 Ma. Thermal modeling of the AFT ages of the samples shows that the Longshoushan experienced significant exhumation during the Late Cretaceous to the Early Cenozoic (~130–25 Ma). The Late Cretaceous exhumation of the Longshoushan may have resulted from the continuous compression between the Lhasa and Qiangtang blocks and the flat slab subduction of the Neo-Tethys oceanic plate, which affected wide regions across the Qinghai-Tibetan Plateau. During the Early Cenozoic, the Longshoushan still experienced exhumation, but this process was caused by the Indian-Eurasian collision. Since this time, the Longshoushan was in a stable stage for approximately 20 Ma and experienced erosion. Since ~5 Ma, obvious tectonic deformation occurred along the entire northern Hexi Corridor, which has also been reported from the peripheral regions of the Qinghai-Tibetan Plateau, especially in the Qilianshan and northeastern margin of the plateau. The AFT ages and the Late Cenozoic deformation of the northern Hexi Corridor all indicate that the present northern boundary of the Qinghai-Tibetan Plateau is situated along the northern Hexi Corridor.  相似文献   

20.
The post-Mesoproterozoic tectonometamorphic history of the Musgrave Province, central Australia, has previously been solely attributed to intracontinental compressional deformation during the 580 -520 Ma Petermann Orogeny. However, our new structurally controlled multi-mineral geochronology results,from two north-trending transects, indicate protracted reactivation of the Australian continental interior over ca. 715 million years. The earliest events are identified in the hinterland of the orogen along the western transect. The first tectonothermal event, at ca. 715 Ma, is indicated by40 Ar/39 Ar muscovite and U e Pb titanite ages. Another previously unrecognised tectonometamorphic event is dated at ca. 630 Ma by Ue Pb analyses of metamorphic zircon rims. This event was followed by continuous cooling and exhumation of the hinterland and core of the orogen along numerous faults, including the Woodroffe Thrust,from ca. 625 Ma to 565 Ma as indicated by muscovite, biotite, and hornblende40 Ar/39 Ar cooling ages. We therefore propose that the Petermann Orogeny commenced as early as ca. 630 Ma. Along the eastern transect,40 Ar/39 Ar muscovite and zircon(Ue Th)/He data indicate exhumation of the foreland fold and thrust system to shallow crustal levels between ca. 550 Ma and 520 Ma, while the core of the orogen was undergoing exhumation to mid-crustal levels and cooling below 600-660℃. Subsequent cooling to 150 -220℃ of the core of the orogen occurred between ca. 480 Ma and 400 Ma(zircon [Ue Th]/He data)during reactivation of the Woodroffe Thrust, coincident with the 450 -300 Ma Alice Springs Orogeny.Exhumation of the footwall of the Woodroffe Thrust to shallow depths occurred at ca. 200 Ma. More recent tectonic activity is also evident as on the 21 May, 2016(Sydney date), a magnitude 6.1 earthquake occurred, and the resolved focal mechanism indicates that compressive stress and exhumation along the Woodroffe Thrust is continuing to the present day. Overall, these results demonstrate repeated amagmatic reactivation of the continental interior of Australia for ca. 715 million years, including at least 600 million years of reactivation along the Woodroffe Thrust alone. Estimated cooling rates agree with previously reported rates and suggest slow cooling of 0.9 -7.0℃/Ma in the core of the Petermann Orogen between ca. 570 Ma and 400 Ma. The long-lived, amagmatic, intracontinental reactivation of central Australia is a remarkable example of stress transmission, strain localization and cratonization-hindering processes that highlights the complexity of Continental Tectonics with regards to the rigid-plate paradigm of Plate Tectonics.  相似文献   

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