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1.
念扎金矿床是近年来最新发现的位于雅鲁藏布江缝合带南侧仁布构造混杂岩带与蚀变闪长岩接触带的大型造山型金矿床.为约束念扎矿床的冷却及剥露历史,利用锆石的U-Pb、(U-Th)/He及磷灰石裂变径迹定年对新鲜及矿化闪长岩年龄进行测定.结果表明,新鲜闪长岩锆石U-Pb年龄为(46.32±0.53)Ma,(U-Th)/He年龄介于(7.14±0.24)Ma到(9.80±0.27)Ma,矿化闪长岩锆石(U-Th)/He年龄介于(8.38±0.24)Ma到(11.19±0.31)Ma之间,两件矿化闪长岩磷灰石裂变径迹年龄分别为(5.9±0.5)Ma和(5.3±1.0)Ma.念扎金矿床自闪长岩固结以来经历了两次快速冷却过程:第一次是从46.3 Ma开始持续到43.6 Ma,温度从750℃降至350℃,冷却速率高达约148℃/Ma;第二次为8.5~2.0 Ma,温度从约200℃降至30℃,冷却速率为26℃/Ma.念扎矿床成矿深度为9.7 km;在8.5 Ma时,矿床被抬升至4.6 km处;从8.5~5.6 Ma,矿床抬升至2.8 km;从5.6~2.0 Ma,念扎矿床被剥露至地表. 相似文献
2.
Birk Härtel William A. Matthews Eva Enkelmann 《Geostandards and Geoanalytical Research》2023,47(3):669-681
The accuracy and validation of geo- and thermochronological dating hinges on the availability of well-characterised age reference materials. The Mesoproterozoic gabbroic anorthosite FC1 from the Duluth Complex, Minnesota is a reference material for zircon U-Pb and a suggested reference material for apatite fission-track dating. We evaluate FC1 as (U-Th)/He reference material, and determine its apatite U-Pb, and zircon and apatite (U-Th)/He age. Our dating results constrain the thermal history of FC1, showing that fast cooling occurred between ~ 1099 and 1040 Ma from ≥ 600 °C to ~ 200 °C. The zircon (U-Th)/He data from air-abraded grains give a robust isochron age of 1037 ± 25 Ma (2s) without overdispersion. The within-grain homogeneity of U and Th, the availability of FC1 zircon, and the absence of radiation-damage effects on the (U-Th)/He age support its use as reference material. Unabraded zircon grains give lower and more dispersed ages, highlighting the usefulness of air abrasion to control for α-ejection in (U-Th)/He dating. Our apatite (U-Th-Sm)/He single-grain ages vary between 180 and 300 Ma. Their wide dispersion argues against the use of FC1 apatite as (U-Th-Sm)/He reference material and makes the interpretation of their low-temperature thermal history complicated. 相似文献
3.
新疆东天山红云滩地区构造-热演化探讨:来自Ar-Ar和(U-Th)/He热年代学的约束 总被引：6，自引：3，他引：3
红云滩岩体位于东天山觉罗塔格西部,对其进行热演化历史研究对于揭示觉罗塔格地区乃至整个东天山地区的构造-热演化历史具有重要意义。本文对红云滩岩体进行黑云母Ar-Ar、锆石(U-Th)/He和磷灰石(U-Th)/He测年,并结合前人的锆石U-Pb测年结果,精细刻画出该岩体自形成以后经历的热演化过程,并据此识别出东天山红云滩地区发生过多期快速抬升冷却事件。黑云母阶段升温Ar-Ar法同位素定年得到的坪年龄为316.9±1.8Ma,单颗粒锆石和磷灰石(U-Th)/He同位素定年得到的平均年龄分别为213.7±9.6Ma和65.5±1.3Ma。热年代学数据及模拟结果表明东天山红云滩地区自晚古生代以来经历了3个快速冷却阶段,分别为:晚石炭世至早二叠世(ca.330~296Ma)、晚三叠世(222~220Ma)、晚白垩世(91~77Ma)。其中,晚石炭世至早二叠世的快速冷却作用是岩体侵位后与围岩热传导冷却及伴随天山造山隆升冷却综合作用的结果,晚三叠世和晚白垩世的两期快速冷却事件分别与羌塘-欧亚板块、Kohistan-Dras岛弧-拉萨地块碰撞的远程效应造成的东天山地区隆升作用有关。新生代以来,红云滩岩体所在的阿奇山-雅满苏地区构造活动相对较弱,未发生较为明显的隆升作用,与天山西段新生代的构造活动有着明显的差异。 相似文献
4.
Charles H. Kasanzu 《地学前缘(英文版)》2017,8(5):999-1007
Borehole and surface samples from the Archean Tanzania Craton were analysed for apatite fission track(AFT) and(U-Th)/He data with the aim of deciphering cooling histories of the basement rocks. Fission track dates from borehole and outcrop samples are Carboniferous-Permian(345± 33.3 Ma to271±31.7 Ma) whereas(U-Th)/He dates are Carboniferous-Triassic(336±45.8 Ma to 213±29 Ma) for outcrop grains and are consistently younger than corresponding AFT dates. Single grain(U-Th)/He dates from the borehole are likely to be flawed by excessive helium implantation due to their very low effective uranium contents, radiation damage and grain sizes. All AFT and(U-Th)/He dates are significantly younger than the stratigraphic ages of their host rocks, implying that the samples have experienced Phanerozoic elevated paleo-temperatures. Considerations of the data indicate removal of up to 9 km overburden since the Palaeozoic.Thermal modelling reveals a protracted rapid cooling event commencing during the early Carboniferous(ca. 350 Ma) at rates of 46 m/Ma ending in the Triassic(ca. 220 Ma). The model also suggests minor cooling during the Cretaceous of the samples to surface temperatures. The suggested later cooling event remains to be tested. The major cooling phase during the Carboniferous is interpreted to be associated with compressional tectonics during the Variscan Orogeny sensu far field induced stresses. Coeval sedimentation in the Karoo basins in the region suggests that most of the cooling of cratonic rocks during the Carboniferous was associated with denudation. 相似文献
5.
川东北地区构造-热演化探讨——来自（U-Th）／He年龄和Ro的约束 总被引：10，自引：0，他引：10
利用镜质组反射率和磷灰石与锆石的(U-Th)/He年龄一起模拟了川东北地区三叠纪以来的构造-热演化特征。结果表明早三叠世的热流值在51～66mW/m2,自晚三叠世至白垩纪随盆地性质由前陆盆地演化为陆内坳陷盆地,热流缓慢降低直至现今的44.5mW/m2。但在晚白垩世—古新世时期受燕山晚期构造运动的影响,热流有一个微弱增高的现象。同时,磷灰石和锆石的He年龄揭示了川东北地区大致在晚白垩世期间开始隆升且抬升剥蚀量较大。因此,磷灰石和锆石的(U-Th)/He年龄可以揭示后期详细的冷却历史。 相似文献
6.
《地学前缘(英文版)》2019,10(6):2153-2166
The Junggar Alatau forms the northern extent of the Tian Shan within the Central Asian Orogenic Belt(CAOB) at the border of SE Kazakhstan and NW China.This study presents the Palaeozoic-Mesozoic post-collisional thermo-tectonic history of this frontier locality using an integrated approach based on three apatite geo-/thermochronometers:apatite U-Pb,fission track and(U-Th)/He.The apatite U-Pb dates record Carboniferous-Permian post-magmatic cooling ages for the sampled granitoids,reflecting the progressive closure of the Palaeo-Asian Ocean.The apatite fission track(AFT) data record(partial)preservation of the late Palaeozoic cooling ages,supplemented by limited evidence for Late Triassic(~230-210 Ma) cooling and a more prominent record of(late) Early Cretaceous(~150-110 Ma) cooling.The apatite(U-Th)/He age results are consistent with the(late) Early Cretaceous AFT data,revealing a period of fast cooling at that time in resulting thermal history models.This Cretaceous rapid cooling signal is only observed for samples taken along the major NW-SE orientated shear zone that dissects the study area(the Central Kazakhstan Fault Zone),while Permian and Triassic cooling signals are preserved in low-relief areas,distal to this structure.This distinct geographical trend with respect to the shear zone,suggests that fault reactivation triggered the Cretaceous rapid cooling,which can be linked to a phase of slab-rollback and associated extension in the distant Tethys Ocean.Similar conclusions were drawn for thermochronology studies along other major NW-SE orientated shear zones in the Central Asian Orogenic Belt,suggesting a regional phase of Cretaceous exhumation in response to fault reactivation at that time. 相似文献
7.
湘中龙山大型金锑矿床成矿时代研究——黄铁矿Re-Os和锆石U-Th/He定年 总被引：4，自引：4，他引：0
龙山金锑矿床是湘中锑-金矿集区最重要的矿床之一,因缺少适合传统放射性同位素定年的矿物,其成矿时代以往未得到很好的限定,制约了对矿床成因的认识。由于分析测试技术的进步,Re-Os同位素定年技术得到了发展,可对热液矿床中形成的低Re、Os含量的硫化物进行较准确可靠的年龄测定,从而可为低温热液矿床的形成时代提供有效制约。锆石U-Th/He同位素定年,也是近年发展和成熟起来的定年技术,对低温热事件极其敏感,同样是约束低温成矿年龄的重要手段之一。本文采用矿床中黄铁矿Re-Os同位素和蚀变围岩中受成矿热事件影响的锆石U-Th/He同位素定年技术,对龙山金锑矿床的成矿时代进行了研究。定年结果显示:热液成因黄铁矿的Re-Os等时线年龄为195±36Ma,对应于印支晚期;锆石U-Th/He年龄为51.2~133.3Ma,经Ft校正后,U-Th/He年龄分布于93.78~258.29Ma之间,平均值为160.7±7.3Ma,对应于燕山早期。该矿床可能发生了200Ma和160Ma的两次成矿作用;或者矿床形成于200Ma左右,但是受到了160Ma左右岩浆热事件的改造,黄铁矿Re-Os年龄代表成矿年龄,而锆石U-Th/He年龄则代表第二期热事件发生的时间。无论是200Ma左右一次成矿,还是另有160Ma左右的成矿作用叠加,这两个年龄分别与区内两期岩浆活动的时间相当,这表明岩浆事件对驱动矿床的形成发挥了重要的作用。 相似文献
8.
《International Geology Review》2012,54(15):1837-1851
The Taipingchuan Cu–Mo deposit is a recently discovered large porphyry deposit located in the north of the Derbugan metallogenic belt of northeastern China. The geochronological data of the deposit yielded a Late Triassic zircon U–Pb age of 202 ± 6 Ma from a granodiorite porphyry that hosts the Cu–Mo mineralization. Measured Re–Os isotopes of seven disseminated molybdenite samples yielded an isochron age of 200 ± 5 Ma with mean square of weighted deviates of 2.7, while those of seven veinlet molybdenite samples also produced an isochron age of 200.1 ± 2.5 Ma and mean square of weighted deviates of 3.3. These isochron ages show that a Cu–Mo mineralization event occurred at ca. 200 Ma. Based on regional tectonic evolution, we propose that the Late Triassic Cu–Mo mineralization of the host porphyry in the Derbugan metallogenic belt was mainly associated with the subduction of the Mongol–Okhotsk Ocean slab under the Ergun block, contrary to previous suggestion that it was related to the subduction of the Mesozoic Palaeo-Pacific plate. 相似文献
9.
湖南锡田花岗岩锆石U-Pb年代学及钨锡成矿时代的探讨 总被引：3，自引：3，他引：0
华南是世界上最大的花岗岩省之一,其中中生代花岗岩最为发育,与之相伴生的是大量钨锡多金属矿床,花岗岩的成因演化因与这些矿床的成矿作用密切相关而备受关注。湖南锡田花岗岩体是该区的一个典型岩体,主要由黑云母花岗岩、黑云母二长花岗岩和细粒花岗岩组成,并伴生有钨锡矿床。本文以湖南锡田花岗岩体为研究对象,对其中不同类型的岩石进行了详细的岩石学和锆石SIMS与LA-ICP-MS U-Pb定年工作。分析结果表明,锡田花岗岩体存在晚三叠世(227~233Ma)和晚侏罗世(150~154Ma)两期岩浆活动,早期的岩浆活动主要分布在岩体北部和中部,晚期岩浆活动仅在岩体中部及东部矿体附近可见,两期岩浆活动具有相同的岩性组合。另外,对含矿花岗岩的锆石U-Pb定年结果表明该地区可能存在晚三叠世的成矿作用,结合前人的工作推断锡田地区钨锡矿的形成受晚三叠世和晚侏罗世两期岩浆事件的影响。 相似文献
10.
I. V. Chernyshev A. G. Bakharev N. S. Bortnikov Yu. V. Goltsman A. B. Kotov G. N. Gamyanin A. V. Chugaev E. B. Sal’nikova E. D. Bairova 《Geology of Ore Deposits》2012,54(6):411-433
The intrusive rocks associated with the large Nezhdaninka gold deposit (Au > 470 t) hosted in the Permian carbonaceous terrigenous sequence have been dated on zircon and rock-forming minerals with precision U-Pb (ID-TIMS) and Rb-Sr methods. The lamprophyre of the dike complex that occurs in the ore field and spatially is related to gold mineralization has concordant U-Pb zircon age (121 ± 1 Ma) and the same isochron Rb-Sr age (121.0 ± 2.8 Ma). The concordant U-Pb zircon age of granodiorite that dominates in the Kurum pluton is 94 ± 1 Ma, whereas the Rb-Sr isochron age of various intrusive rocks from this pluton is 1–4 Ma younger. This difference is caused by long-term cooling of the Kurum pluton and later closure of Rb-Sr isotopic system of biotite (300–350°C) and other rock-forming minerals as compared with U-Pb isotopic system of zircon (～ 900°C). The Rb-Sr age of quartz diorite from the Gel’dy group of stocks (92.6 ± 0.8 Ma) coincides within uncertainty limits with the age of the Kurum pluton. Thus, the rocks pertaining to two epochs of magmatic activity, which developed in the South Verkhoyansk Foldbelt and divided by a time span of 25–28 Ma, are documented in the Nezhdaninka ore field. Taking into account that the age of gold mineralization is no less than 120 Ma, the data obtained allow us to specify the previously proposed formation model of the Nezhdaninka deposit. These data give grounds to rule out the Late Cretaceous Kurum pluton and the Gel’dy group of stocks from constituents of the ore-magmatic system, and to suggest that an Early Cretaceous deep-seated magma source existed beneath the deposit. Along with host terrigenous rocks, this magma source participated in the supply of matter to the hydrothermal system. The Nd, Sr, and Pb isotopic systematics of igneous rocks and ore mineralization in the Nezhdaninka ore field show that the Early and Late Cretaceous magma sources were formed in the Precambrian crust dated at ～1.8 Ga. 相似文献