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1.
The contractional structures in the southern Ordos Basin recorded critical evidence for the interaction between Ordos Basin and Qinling Orogenic Collage. In this study, we performed apatite fission track(AFT) thermochronology to unravel the timing of thrusting and exhumation for the Laolongshan-Shengrenqiao Fault(LSF) in the southern Ordos Basin. The AFT ages from opposite sides of the LSF reveal a significant latest Triassic to Early Jurassic time-temperature discontinuity across this structure. Thermal modeling reveals at the latest Triassic to Early Jurassic, a ~50°C difference in temperature between opposite sides of the LSF currently exposed at the surface. This discontinuity is best interpreted by an episode of thrusting and exhumation of the LSF with ~1.7 km of net vertical displacement during the latest Triassic to Early Jurassic. These results, when combined with earlier thermochronological studies, stratigraphic contact relationship and tectono-sedimentary evolution, suggest that the southern Ordos Basin experienced coeval intense tectonic contraction and developed a north-vergent fold-and-thrust belt. Moreover, the southern Ordos Basin experienced a multi-stage differential exhumation during Mesozoic, including the latest Triassic to Early Jurassic and Late Jurassic to earliest Cretaceous thrust-driven exhumation as well as the Late Cretaceous overall exhumation. Specifically, the two thrust-driven exhumation events were related to tectonic stress propagation derived from the latest Triassic to Early Jurassic continued compression from Qinling Orogenic Collage and the Late Jurassic to earliest Cretaceous intracontinental orogeny of Qinling Orogenic Collage, respectively. By contrast, the Late Cretaceous overall exhumation event was related to the collision of an exotic terrain with the eastern margin of continental China at ~100 Ma.  相似文献   

2.
《Gondwana Research》2013,23(3-4):910-927
We present LA-ICP-MS (laser ablation inductively coupled plasma mass spectrometry) U–Pb detrital and igneous zircon data of poly-deformed metamorphic and igneous rocks of the Ayú area, southern Mexico. These rocks were previously inferred to be part of the Late Paleozoic Acatlán Complex, but new age data indicate that they formed in the Mesozoic and should be placed in the newly designated Ayú Complex. The Ayú Complex comprises polydeformed metasedimentary rocks (Chazumba Lithodeme) of a turbidite-like protolith that are intercalated with boudinaged ortho-amphibolites with transitional arc- to MORB tholeiitic geochemistry. In the south, the metasedimentary sequence is affected by a ca. 171 Ma partial melting which formed the Magdalena Migmatite. Migmatization was accompanied by 171–168 Ma intrusions of granodioritic, dioritic, and granitic dikes and sheets as well as pegmatite bodies, which are characterized by inherited zircon populations of ca. 260–290, 320–360, 420–480, 880–990, and 1080–1250 Ma that are also found in the Chazumba Lithodeme. U–Pb (detrital zircon) dating of seven metasedimentary samples from the migmatized and unmigmatized Chazumba Lithodeme yielded youngest detrital zircons and clusters of 192, 198, 214, 250, 266, and 291 Ma, and are interpreted to reflect the Late Triassic–Middle Jurassic deposition of turbiditic rocks. The transitional arc–tholeiitic geochemistry of the Chazumba amphibolites is consistent with turbidite sedimentation in a back-arc environment along a rifted passive margin, close to a contemporaneous magmatic arc. Inferred flattening of the subduction zone led to subduction erosion during the Early–Middle Jurassic and underthrusting of the Chazumba Lithodeme to depths equivalent to amphibolite facies metamorphism. Steepening of the subducting slab and diachronous rifting within the Gulf of Mexico contributed to extensional tectonics recorded on the Mexican mainland and facilitated the tectonic exhumation of the Chazumba Lithodeme by normal faulting along the reactivated Providencia shear zone during the Middle–Late Jurassic. More generally, the documentation of arc-back arc assemblages in the Ayú Complex requires deposition adjacent to a subducting ocean, and thus supports a Pangea-A reconstruction that was synchronous with the breakup of Pangea.  相似文献   

3.
Apatite fission‐track analyses on samples from eastern Sardinia document a complex tectonic history, whose reconstruction is problematic because of the reactivation of faults and structures at different times from Jurassic to Miocene. The oldest ages (150–154 Ma) have been detected on the southern margin of the Gulf of Orosei and are related to the extensional tectonics that characterize the European passive margin during Early and Middle Jurassic times. Thermal modelling of these data allows reconstruction of the burial history of the Mesozoic basin and estimation of a sedimentary thickness of 2000 m. Part of these sediments was eroded during the following uplift, documented by mid‐Cretaceous fission‐track ages. A further exhumation episode of Eocene age has been revealed by fission‐track data on granite samples, and has been inferred to be related to the Alpine orogenic phase. This tectonic episode caused the exhumation of crustal blocks bound by faults that were finally reactivated during the Late Oligocene–Early Miocene.  相似文献   

4.
Summary Hornblende thermobarometry has been widely used to estimate the emplacement pressure (P) and temperature (T) of calc-alkaline igneous rocks. Application of hornblende thermobarometry to the newly discovered Carboniferous granitic plutons from the Inner Mongolia Paleo-uplift (IMPU) provides useful information on the exhumation and geotectonic evolution of the northern margin of the North China block (NCB) during the Late Paleozoic to Early Mesozoic. Emplacement depths estimated from aluminum-in-hornblende geobarometry indicate that the Longhua, Daguangding and Boluonuo plutons were emplaced at depths of 15.7–18.7 km. Temperatures of emplacement calculated with the hornblende-plagioclase thermometer range from 676 °C to 780 °C. Because most of these plutons are unconformably overlain by Jurassic-Cretaceous volcanic or sedimentary rocks and, regionally, the oldest strata overlying them are the Nandaling and Xiahuayuan Formations of Early Jurassic age, most of these plutons must have been exposed at the surface prior to the Early Jurassic. Therefore, the large-scale uplift and exhumation of the IMPU occurred from the Late Carboniferous to Early Jurassic; at least 15 km thick crustal rocks in the IMPU must have been eroded during this period. It is also inferred that the IMPU was not always an uplifted domain from the Neoproterozoic to Early Triassic. Some Meso-Neoproterozoic and, possibly Paleozoic sedimentary rocks or Early-Middle Triassic volcanic rocks were present in the IMPU until the Late Triassic, but were almost entirely eroded before the end of Triassic. The exhumation of the crystalline rocks and formation of the IMPU is a result of this strong erosion during the Late Paleozoic to Early Mesozoic. Supplementary material to this paper is available in electronic form at Tables 1-2 available as electronic supplementary material  相似文献   

5.
周建波  韩伟  宋明春 《岩石学报》2016,32(4):1171-1181
胶莱盆地位于苏鲁造山带的北缘,其莱阳群沉积对反演郯庐断裂和苏鲁造山带中生代的折返过程具有重要的制约作用。本文利用LA-ICP-MS方法对莱阳盆地的莱阳群碎屑岩和青山群火山岩进行锆石U-Pb年龄测定,分析其年龄谱特征,探讨其沉积物源区,进而为苏鲁造山带的折返机制提供依据。(1)莱阳盆地发育莱阳群和青山群为代表的中生代沉积岩,锆石年龄测试得到莱阳群形成时代为125±0.6Ma;青山群形成时代为119±1Ma,表明两者都是早白垩世中-晚期的沉积产物;(2)超高压带北缘莱阳盆地与合肥盆地的碎屑锆石年龄谱对比表明,莱阳盆地的沉积物无论沉积时代还是物源区均明显不同与郯庐断裂西侧的合肥盆地,表明郯庐断裂应该形成于两个盆地形成之前,可能为三叠纪-早侏罗世之间;(3)莱阳盆地内发育大量的华北型碎屑物质,进一步表明在扬子大陆板块俯冲过程中华北板块曾经仰冲到扬子板块之上;(4)莱阳盆地发育少量的新元古代岩浆和印支期变质锆石的年龄,表明早白垩世苏鲁超高压变质岩已经折返到地表;(5)超高压变质岩与中生代岩浆岩同时作为莱阳盆地的物源,结合五莲拆离断层的同期活动和莱阳盆地的同时代沉积,说明苏鲁超高压带中生代的折返具有与变质核杂岩类似的大型伸展构造背景。  相似文献   

6.
王枫  许文良  葛文春  杨浩  裴福萍  吴韦 《岩石学报》2016,32(4):1129-1140
敦化-密山断裂带是郯庐断裂北段的重要分支之一,其大规模左行走滑发生的时限以及平移距离一直存在较大争议。本文系统地总结了松嫩-张广才岭地块东缘、佳木斯地块以及兴凯地块之上古生代-中生代火成岩的锆石U-Pb年代学资料,结合其空间分布特征,对敦化-密山断裂带的平移时限及距离提供了制约。研究表明,松嫩-张广才岭地块东缘与兴凯地块在古生代-中生代期间具有类似的岩浆活动历史,两个地块之上该时期的岩浆作用可以划分为8个主要期次:中-晚寒武世(ca.500~516Ma)、早奥陶世(ca.480~486Ma)、晚奥陶世(ca.450~456Ma)、中志留世(ca.426~430Ma)、早二叠世(ca.285~292Ma)、晚二叠世(ca.255~260Ma)、晚三叠世(ca.202~210Ma)和早侏罗世(ca.185~186Ma)。相比之下,佳木斯地块中的古生代-中生代早期岩浆事件则集中在晚寒武世(~492Ma)、晚泥盆世(~388Ma)、早二叠世(~288Ma)、晚二叠世(~259Ma)和早侏罗世(~176Ma),而晚奥陶世-志留纪和晚三叠世的岩浆活动在佳木斯地块未见报道。早白垩世晚期(ca.105~110Ma)和晚白垩世(ca.90~94Ma)的岩浆活动在三个地块均存在。上述结果表明兴凯地块东缘与松嫩-张广才岭地块东缘在早古生代经历了共同的地质演化历史,而中生代早期,兴凯地块西缘与松嫩-张广才岭地块东缘经历了同样的岩浆作用历史。上述结果暗示,敦化-密山断裂可能经历了至少两次平移,分别发生在中-晚二叠世-早三叠世和中-晚侏罗世-早白垩世,推测其总的平移距离约400km。结合研究区中生代期间的构造演化历史,敦化-密山断裂中生代的左行平移应与中-晚侏罗世-早白垩世期间古太平洋板块(Izanagi板块)的斜向俯冲相联系。  相似文献   

7.
龙门山冲断隆升及其走向差异的裂变径迹证据   总被引：4，自引：1，他引：3  
大量的低温年代学研究用来讨论龙门山晚新生代的隆升,但很少涉及其走向差异和中生代隆升。本文分别沿龙门山北、中、南段3条剖面进行了锆石和磷灰石裂变径迹测试,结合已有的热年代学数据,以期揭示整个中-新生代期间龙门山隆升历史及其时空变化。中生代以来,龙门山主要有印支期(约200 Ma)、早白垩世末(约100 Ma)、早新生代(65～30 Ma)以及晚中新世(15～9 Ma)等或快或慢的冷却事件,总体上经历了中生代至早新生代的缓慢冷却和晚新生代快速冷却2个阶段,快速剥露开始于15～9 Ma,剥蚀速率由早期的0.1 mm/a增加到0.15～0.3 mm/a左右,局部可达0.9 mm/a左右。走向上,龙门山北段相对偏小的锆石裂变径迹年龄和相对偏大的磷灰石裂变径迹年龄反映其在中生代较中、南段隆升更快,而裂变径迹年龄总体上从北段向中、南段减小,表明中、南段在新生代发生了更快的隆升。倾向上,多种热年代学数据显示新生代期间在北川断裂和彭灌断裂两侧存在明显的差异剥露,这种差异在中、南段表现比北段更为突出。龙门山晚新生代快速隆升和剥露是青藏高原区域隆升背景上叠加的冲断活动所致,而非下地壳流动驱动。  相似文献   

8.
Two case histories are presented to give evidences for sediment cooling during increasing burial depth due to heat flow decrease at the end of crustal stretching in extensional settings. The first refers to the Lower Cretaceous succession accumulated in a strongly subsiding trough within the Sirt Basin (Libya); the second relates to the Mesozoic succession of the Lombardian Basin (NW Italy) formed during Late Triassic–Early Jurassic rifting of the northern margin of the Adriatic microplate. In both cases, heat flow decreasing at the end of crustal stretching overbalanced the thermal effect of increasing burial depth causing a net cooling of rocks. These examples provide an alternative to exhumation for explaining cooling events recorded by rifting sedimentary sequences.  相似文献   

9.
Carboniferous‐Permian volcanic complexes and isolated patches of Upper Jurassic — Lower Cretaceous sedimentary units provide a means to qualitatively assess the exhumation history of the Georgetown Inlier since ca 350 Ma. However, it is difficult to quantify its exhumation and tectonic history for earlier times. Thermochronological methods provide a means for assessing this problem. Biotite and alkali feldspar 40Ar/39Ar and apatite fission track data from the inlier record a protracted and non‐linear cooling history since ca 750 Ma. 40Ar/39Ar ages vary from 380 to 735 Ma, apatite fission track ages vary between 132 and 258 Ma and mean track lengths vary between 10.89 and 13.11 μm. These results record up to four periods of localised accelerated cooling within the temperature range of ～320–60°C and up to ～14 km of crustal exhumation in parts of the inlier since the Neoproterozoic, depending on how the geotherm varied with time. Accelerated cooling and exhumation rates (0.19–0.05 km/106 years) are observed to have occurred during the Devonian, late Carboniferous‐Permian and mid‐Cretaceous — Holocene periods. A more poorly defined Neoproterozoic cooling event was possibly a response to the separation of Laurentia and Gondwana. The inlier may also have been reactivated in response to Delamerian‐age orogenesis. The Late Palaeozoic events were associated with tectonic accretion of terranes east of the Proterozoic basement. Post mid‐Cretaceous exhumation may be a far‐field response to extensional tectonism at the southern and eastern margins of the Australian plate. The spatial variation in data from the present‐day erosion surface suggests small‐scale fault‐bounded blocks experienced variable cooling histories. This is attributed to vertical displacement of up to ～2 km on faults, including sections of the Delaney Fault, during Late Palaeozoic and mid‐Cretaceous times.  相似文献   

10.
根据对东昆仑地区东段哈拉郭勒—哈图一带不同高度基岩的系列锆石裂变径迹年龄分析，结合磷灰石裂变径迹年龄分析和中酸性侵入岩角闪石压力计分析揭示了东昆仑东段中生代的岩石隆升剥露冷却历史．巴隆哈图一带中酸性侵入岩角闪石压力计分析结果反映晚海西—印支期以来的总体剥露幅度约8～9km，早二叠世至晚三叠世初剥蚀作用极为缓慢，大约为20～40m／Ma．不同高程样品的锆石裂变径迹年龄分析结果揭示了东昆仑地区东段在中晚侏罗世处于缓慢的岩石隆升剥露阶段，其中中侏罗世相对较快，抬升速率77～88m／Ma，晚侏罗世相对较慢，抬升速率小于37m／Ma，且呈减慢趋势，这种减慢趋势反映了早中侏罗世之交强构造抬升期后的逐渐衰退．锆石裂变径迹—磷灰石裂变径迹年龄分析结果反映了中侏罗世以来的剥蚀速率一般不超过55m／Ma，岩石的剥蚀速率与岩石的抬升速率基本为同一量级，中侏罗世—白垩纪剥蚀作用与岩石抬升作用基本处于平衡状态。  相似文献   

11.
低温热年代技术已经广泛应用于造山带的剥露作用和古地形演化的研究。本文对黄陵隆起进行了裂变径迹和(U-Th)/He热年代学研究,分析计算其隆升剥露速率和厚度,恢复黄陵隆起中新生代古地形。依据岩石样品冷却历史计算出的剥露速率以及剥露厚度结果,综合黄陵隆起现今地形起伏,均衡回弹作用以及古海平面变化情况,获得了黄陵隆起早侏罗世、早白垩世、晚白垩世、晚始新世以及现今5个时期的古地形变化情况。结果表明黄陵隆起地形表现为持续降低的趋势,并存在两期剧烈的隆升剥露阶段。分析认为,白垩纪(140~80 Ma±),黄陵隆起的快速隆升剥露作用与秦岭大别造山带大规模的挤压作用密切相关,晚始新世以来(40~0 Ma)黄陵隆起的快速抬升剥露作用则是对喜山期构造运动的响应。  相似文献   

12.
In Morocco, it is generally considered that post‐Hercynian vertical movements were limited to the Atlas system, the passive continental margin and the Rif. Apatite FT and He ages from the Moroccan Meseta (Rehamna and Zaer Massif) document instead two episodes of subsidence and exhumation in Jurassic‐Early Cretaceous and during the Late Cretaceous to Neogene. The Meseta subsided to >3 km depth during the Late Triassic to Middle Jurassic and was exhumed to the surface before the Late Cretaceous, during the rift and post‐rift stages of Central Atlantic opening. Erosion of the exhuming rocks is responsible for a thick package of terrigenous sands found in the Moroccan offshore and elsewhere along the NW Africa margin. About 1 km of subsidence affected the Meseta during the Late Cretaceous to Eocene. During the Neogene, these areas were brought back to the surface in association with bimodal folding with wavelengths of 100–150 km and >500 km.  相似文献   

13.
ABSTRACT New radiolarian biostratigraphical data have shed light on the Mesozoic tectonic evolution of South-Tethys in the Baer–Bassit region of NW Syria. Radiolarian assemblages of Late Triassic, Middle Jurassic and Early Cretaceous age were extracted from radiolarites in five measured sections. The results are compared with published radiolarian ages from the Mamonia Complex, western Cyprus. These two areas are interpreted as preserved fragments of the conjugate margins of a small South Tethyan oceanic basin formed by Triassic rifting. In the southerly (i.e. Arabian) margin, proximal successions were dominated by shallow-water-derived carbonate, whereas distal successions reveal seamount-type alkaline/peralkaline volcanism, dated as both Late Triassic and Middle Jurassic–Early Cretaceous. Along the inferred northern margin (i.e. western Cyprus) proximal successions are dominantly terrigenous, whereas distal settings include Late Triassic oceanic crust and seamount-type lavas.  相似文献   

14.
In the northern part of Tunisia, close to Testour/Slouguia, new observations and updated biostratigraphy make it possible to highlight the relation between the Triassic saliferous mass and the surrounding Mesozoic beds (T. M.). Near the (T. M.) boundary, the formations observed consist dominantly of Triassic evaporites reworked in the Early and Late Albian deep-water sedimentary deposits. Throughout the studied area, Jurassic rocks are absent. We propose to interpret the Chitana-Ed Djebs structure originally emplaced as gravitational stretch masses in a passive margin in the same way as the salt bodies of widespread salt province in the Gulf of Mexico. A reconstructed schematic position of the Chitana-Ed Djebs salt body displays a scenario of setting of the salt mass on a submarine palaeo-slope. Moreover, the starting clues of the paroxysmal event of the Late Mesozoic tectonic inversion clearly fossilized through the discordance of the Middle Eocene–Early Lutetian limestone on the Albian series.  相似文献   

15.
Cratons are conventionally assumed to be areas of long-term stability. However, whereas Precambrian basement crops out across most of the Baltic Shield, Palaeozoic and Mesozoic sediments rest on basement in southern Sweden, and thus testify to a complex history of exhumation and burial. Our synthesis of published stratigraphic landscape analysis and new apatite fission-track analysis data reveals a history involving five steps after formation of the extremely flat, Sub-Cambrian Peneplain. (1) Cambrian to Lower Triassic rocks accumulated on the peneplain, interrupted by late Carboniferous uplift and exhumation. (2) Middle Triassic uplift removed the Palaeozoic cover along the south-western margin of the shield, leading to formation of a Triassic peneplain with a predominantly flat relief followed by deposition of Upper Triassic to Lower Jurassic rocks. (3) Uplift that began during the Middle Jurassic to earliest Cretaceous caused denudation leading to deep weathering that shaped an undulating, hilly relief that was buried below Upper Cretaceous to Oligocene sediments. (4) Early Miocene uplift and erosion produced the South Småland Peneplain with scattered hills. (5) Early Pliocene uplift raised the Miocene peneplain to its present elevation leading to reexposure of the sub-Cretaceous hilly relief near the coast. Our results thus provide constraints on the magnitude and timing of episodes of deposition and removal of significant volumes of Phanerozoic rocks across the southern portion of the Baltic Shield. Late Carboniferous, Middle Triassic and mid-Jurassic events of uplift and exhumation affected wide areas beyond the Baltic Shield, and we interpret them as epeirogenic uplifts accompanying fragmentation of Pangaea, caused by accumulation of mantle heat beneath the supercontinent. Early Miocene uplift affected north-west Europe but not East Greenland, and thus likely resulted from compressive stresses from an orogeny on the Eurasian plate. Early Pliocene uplift related to changes in mantle convection and plate motion affected wide areas beyond North-East Atlantic margins.  相似文献   

16.
The Harz Mountains and the adjacent Subhercynian Cretaceous Basin figure as the most prominent surface representative for Late Cretaceous inversion structures in Central Europe. Facies, depositional architecture and provenance of the basin fill reflect mechanisms and timing of the exhumation of the Harz. From Hauterivian to Early Santonian there is no evidence for detrital input from the nearby Harz area. Sediments are mature quartzarenites derived from Paleozoic basement rocks and/or recycled Permian to Mesozoic sedimentary rocks. This situation changed drastically in Middle to Late Santonian when freshly exhumed and eroded Mesozoic sedimentary cover rocks of the Harz were delivered into the basin. Feldspar and lithoclasts reflect erosion of Triassic and, in places, Jurassic to Turonian strata. Apatite and garnet in heavy mineral spectra are derived from largely unweathered Lower Triassic Buntsandstein as indicated by apatite and garnet chemistry. In Early Campanian, Paleozoic lithoclasts indicate erosion cutting down into the basement of the Harz. Simultaneous strong decrease of feldspar, garnet and apatite suggest an almost complete removal of the 2–3 km thick Mesozoic cover of the Harz within only 2–4 Myr. This translates into an exhumation rate of approximately 1 mm/a consistent with apatite fission track data from granitoid rocks of the Harz Mountains.  相似文献   

17.
Northwestern China belts result from the Palaeozoic collage of Central Asia and the subsequent reactivations due to far-field effects of the Mesozoic Tibetan and the Cenozoic Himalayan collisions. Triassic is a crucial period to understand and decipher the tectonics related to these two episodes. About 250 oriented palaeomagnetic cores from 43 sites were collected from six sections of Upper Permian to Late Triassic sandstone, in South and West Junggar, Northwestern China. Thermomagnetic, IRM and hysteresis measurements reveal magnetite as the main carrier of the magnetic remanence with minor hematite and maghemite. Stepwise thermal demagnetisation has generally isolated two components. The low temperature component, up to 300–350 °C, displays a direction consistent with the present-day geomagnetic field. The locality-mean directions related to the high temperature component (above 350 °C) were also calculated. Two out of six sections display intense viscous magnetisation and the occurrence of maghemite reveals a possible Cenozoic chemical remagnetisation for these two localities. For the other four localities, we assume that the magnetisation is primary because: (1) AMS measurements reveal a primary fabric, (2) there are local occurrences of antipodal polarities, and (3) palaeolatitudes of tilt-corrected poles are compatible with previous studies. The consistency between the Early Triassic poles of West and South Junggar indicates that Junggar evolved as a rigid block only since Early Mesozoic. The comparison of the Late Palaeozoic and the Early Mesozoic poles of Junggar and those of Siberia and Tarim shows major rotations between the Late Permian and the Late Jurassic–Early Cretaceous. These periods of discrete rotations are characterized by strike-slip faulting in Tianshan and Altai and they may correlate with the major episodes of coarse-grained detrital sedimentation and uplift of the range. Especially, the counter-clockwise rotations of Junggar relative to Tarim and Siberia, which occurred between the Early and the Late Triassic and between the Late Triassic and the Late Jurassic, are accommodated by transpressive tectonics in the Tianshan and the Altai belts. This reactivation is a far-field effect of Tibetan blocks diachronous collisions. Therefore, these first Triassic palaeomagnetic results from Junggar infer that post-Carboniferous rotations were due to the combined effect of the post-orogenic transcurrent movement and the Mesozoic oblique reactivation.  相似文献   

18.
ABSTRACT

The Mesa Central of Mexico (MC) is an elevated plateau located 2000 m above sea level in central Mexico, where intrusions outcrop that register the history of exhumation-erosion occurring during the Late Cretaceous-Paleogene. The tectonic history of the region records formation of the Late Cretaceous-Paleogene ‘Mexican orogen’; this was followed by extension of the entire region and several plutons were then exhumed. The age and magnitude of the crustal uplift and erosion occurring during exhumation has not been addressed to date. Therefore, this study reports the crystallization and cooling ages of two plutons, the Tesorera Granodiorite and the Comanja Granite, and estimates their emplacement depths. Based on these data, the exhumation age of the Tesorera Granodiorite is estimated to be between ~73 Ma and ~63 Ma at an exhumation rate of ~528 m/m. y. and that of the Comanja Granite is 52 Ma and 48 Ma at an exhumation rate of ~2500 m/m. y. Exhumation-erosion event of the Tesorera Granodiorite was located on the trace of the San Luis-Tepehuanes Fault System and that of the Comanja Granite on the a trace of the El Bajío Fault System. Furthermore, the high exhumation rate in the Comanja Granite suggests that gravitational collapse played an important role during exhumation.  相似文献   

19.
为更好地理解燕山西段晚中生代岩浆活动的时空演化规律,根据近年来取得的高精度锆石U-Pb测年数据,本文研究北京地区中生代侵入岩的时间序列。北京地区中生代侵入活动发生在晚三叠世末-早侏罗世初、晚侏罗世-早白垩世两个阶段。现有资料尚无法确证北京地区有中侏罗世时期的深成岩浆活动,这表明前人厘定的八达岭杂岩带和北京地区中生代侵入岩岩石谱系问题甚多,未能反映北京地区中生代岩浆侵入事件的真实序列。根据侵入岩岩石组合和地球化学特征,燕山西段侏罗-白垩纪地壳发生减薄、进入后造山阶段的时限应该在130~125 Ma之后。建立完整的燕山西段晚中生代侵入活动时空分布格局,还需更多的野外工作和高精度锆石U-Pb年龄数据。  相似文献   

20.
Southern Mexico is a key area for unraveling the tectonic evolution of North America because it contains the stratigraphic and structural record of the major tectonic events that shaped this continental mass, such as the breakup of Pangea and the growth of the North America Cordilleran Orogeny. However, multiple reactivations of faults and erosion of the stratigraphic record do not permit to adequately assess the timing of these tectonic events. Although most authors suggested that lithospheric extension and exhumation of continental blocks during Pangea breakup started in Mexico by Early Jurassic time, works published in the last decade provide an increasing number of thermo-tectonic evidence of an earlier phase of continental thinning. In this work, we present detrital apatite thermochronological and geochemical data (trace elements including rare earth elements) from fluvial deposits of the Tianguistengo formation, which is the oldest stratigraphic unit of the Otlaltepec Basin, a major basin in southern Mexico that has been linked to Pangea breakup. Our data show that at least a part of the Tianguistengo formation was derived from the adjacent Pennsylvanian–Cisuralian Totoltepec pluton. Apatite fission-track-based time–temperature modelling for unreset apatite populations suggests that the main exhumation of the Totoltepec pluton, which prompted the deposition of a part of the Tianguistengo formation, took place during Late Triassic time. Thus, our results suggest that Pangea breakup in southern Mexico started at least by Middle–Late Triassic time (240–230 Ma), as it is recorded in the Otlaltepec Basin.  相似文献   

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