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1.
Laser Raman spectroscopy and cathodoluminescence (CL) images reveal that most zircon separated from paragneiss and orthogneiss in drillhole CCSD‐PP2 at Donghai, south‐western Sulu terrane, retain low‐P mineral‐bearing inherited cores, ultrahigh‐pressure (UHP) mineral‐bearing mantles and low‐P mineral‐bearing (e.g. quartz) rims. SHRIMP U–Pb analyses of these zoned zircon identify three discrete and meaningful age groups: Proterozoic protolith ages (> 680 Ma) are recorded in the inherited cores, the UHP metamorphic event in the coesite‐bearing mantles occurred at 231 ± 4 Ma, and the late amphibolite facies retrogressive overprint in the quartz‐bearing rims was at 211 ± 4 Ma. Thus, Neoproterozoic supracrustal protoliths of the Sulu UHP rocks were subducted to mantle depths in the Middle Triassic, and exhumed to mid‐crustal levels in the Late Triassic. The exhumation rate deduced from the SHRIMP data and metamorphic P–T conditions is 5.0 km Ma?1. Exhumation of the Sulu UHP terrane may have resulted from buoyancy forces after slab break‐off at mantle depths. 相似文献
2.
胶东地区是目前我国最重要的金矿产地,已累积探明黄金储量接近5000t。金矿在胶东地区分布非常不均,主要集中在胶北地体,而胶东东部地区金矿产出较少。晚侏罗世的玲珑花岗岩是胶北金矿区最重要的赋矿围岩之一。虽然胶东东部同样有晚侏罗世花岗岩发育,但赋存金矿较少,因此前人对东部这些花岗岩体的研究相对较少。本文选取胶东东部的文登岩体和垛崮山岩体进行了锆石U-Pb定年和Hf同位素分析,同时收集整理了胶北地体的玲珑岩体数据,通过开展胶东东部及西北部同一时期岩体的差异性研究,为该区金成矿作用的研究提供重要线索。分析结果显示,文登岩体和垛崮山岩体的形成时代为晚侏罗世(~160Ma),与玲珑岩体时代一致。三个岩体均含有较多的三叠纪(~230Ma)和新元古代(~780Ma)的继承锆石,表明晚侏罗世花岗岩的岩浆源区主要为经历了超高压变质作用的扬子板块。不同的是,玲珑岩体中有更多的华北板块物源的年龄记录(~1400Ma、~1700Ma、~2500Ma),垛崮山岩体中这些年龄的继承锆石少于玲珑岩体,而文登岩体更少。文登岩体、垛崮山岩体的新生岩浆锆石ε;(t)值范围分别为-30.7~-20.3和-27.5~-17.9,玲珑岩体的新生岩浆锆石ε;(t)值的变化范围更广,在-29.3~-9.3之间,而且呈现出从文登岩体到垛崮山岩体到玲珑岩体,ε;(160Ma)值逐渐增高的现象。其原因可能是扬子板块与华北板块碰撞后,幔源岩浆底侵并诱发加厚的地壳发生部分熔融,形成花岗岩。在此过程中胶北地体深部受到幔源物质的影响,从而对金及成矿相关元素产生一定的预富集作用,而同时期胶东东部地区未受到明显的地幔物质影响,可能是该区金矿产出较少的原因之一。 相似文献
3.
LIU Fulai XU Zhiqin XUE Huaimin ZHOU Kaifu Institute of Geology Chinese Academy of Geological Sciences Bejing 《《地质学报》英文版》2006,80(3):336-348
Laser Raman spectroscopy and cathodoluminescence (CL) images show that most zircon crystals separated from paragneiss in the main drill hole of the Chinese Continental Scientific Drilling Project (CCSD-MH) at Maobei, southwestern Sulu terrane, contain low-pressure mineral-bearing detrital cores, coesite-bearing mantles and quartz-bearing or mineral inclusion-free rims. SHRIMP U Pb dating on these zoned zircons yield three discrete and meaningful age groups. The detrital cores yield a large age span from 659 to 313 Ma, indicating the protolith age for the analyzed paragneiss is Paleozoic rather than Proterozoic. The coesite-bearing mantles yield a weighted mean age of 228 ± 5 Ma for the UHP event. The quartz-bearing outmost rims yield a weighted mean age of 213 ± 6 Ma for the retrogressive event related to the regional amphibolite facies metamorphism in the Sulu UHP terrane. Combined with previous SHRIMP U-Pb dating results from orthogneiss in CCSD-MH, it is suggested that both Neoproterozoic granitic protolith and Paleozoic sedimentary rocks were subducted to mantle depths in the Late Triassic. About 15 million years later, the Sulu UHP metamorphic rocks were exhumed to mid-crustal levels and overprinted by an amphibolite-facies retrogressive metamorphism. The exhumation rate deduced from the SHRIMP data and metamorphic P-T conditions is about 6.7 km/Ma. Such a fast exhumation suggests that the Sulu UHP paragneiss and orthogneiss returned towards the surface as a dominant part of a buoyant sliver, caused as a consequence of slab breakoff. 相似文献
4.
Thin layers and lenses of granitic leucosome are widely distributed within amphibolites, paragneisses and orthogneisses of the Sulu UHP terrane. They are parallel to, or cross‐cut, foliations in the host rocks at different scales and show evidence of coalescence and migration to form centimetre‐ to decimetre‐scale segregations. Variously migmatized rocks extend at least 350 km from SW Sulu (Maobei) to NE Sulu (Weihai), in a band at least 50 km wide. A combined study of mineral inclusions, cathoduluminescence (CL) images, U–Pb LA‐ICP‐MS dates, and in‐situ trace element compositions of zircon provide clear evidence on the nature and timing of partial melting in these UHP rocks. Most zircon from the granitic leucosomes occurs as distinct overgrowths around inherited (igneous or metamorphic) cores or as new, euhedral crystals. The overgrowths and new crystals commonly show perfectly euhedral shapes, have pronounced oscillatory zoning and contain felsic mineral inclusions, such as Kfs + Pl + Qtz ± Ilm ± monazite (Mon). In contrast, the inherited igneous or metamorphic cores are rounded or irregular, contain low‐P or UHP mineral inclusions and show clear dissolution textures. These data suggest that the new zircon is anatectic in origin and that it grew during partial melting of the UHP rocks. The REE patterns of the anatectic zircon show steep slopes from the HREE to LREE with strongly to moderately negative Eu anomalies (Eu/Eu* = 0.31–0.72) and pronounced positive Ce anomalies (Ce/Ce* = 6.8–26.5). Abundant U–Pb spot analyses of the anatectic zircon reveal two discrete and meaningful ages of partial melting within the Sulu UHP terrane. Anatectic zircon from 12 granitic leucosomes within amphibolites, paragneisses, and orthogneisses from Sulu UHP slices II and III yields consistent mean U–Pb ages of 219.0 ± 1.2 to 218.3 ± 1.6 Ma, 218.8 ± 2.0 to 217.3 ± 1.7 Ma and 218.2 ± 1.4 to 215.0 ± 1.5 Ma, respectively. In contrast, anatectic zircon from six granitic leucosomes within paragneisses and orthogneisses from Sulu UHP slice III records younger mean U–Pb ages of 151.9 ± 1.3 to 151.1 ± 1.8 Ma and 155.9 ± 1.8 to 153.7 ± 1.7 Ma, respectively. These data imply that the Sulu UHP terrane experienced two Mesozoic partial melting events. The first partial melting event (219–215 Ma) was probably associated with a Late Triassic granulite facies stage of ‘hot’ exhumation, whereas the second (156–151 Ma) is interpreted as the result of Middle‐Late Jurassic extension and thinning of the previously thickened crust of the Sulu UHP terrane. Both partial melting events induced extensive retrograde metamorphism of the eclogites and their country rocks. 相似文献
5.
Da Wang Jeffrey D. Vervoort Christopher M. Fisher Hui Cao Guangxu Li 《Journal of Metamorphic Geology》2019,37(5):611-631
Dating ultra‐high–pressure (UHP) metamorphic rocks provides important timing constraints on deep subduction zone processes. Eclogites, deeply subducted rocks now exposed at the surface, undergo a wide range of metamorphic conditions (i.e. deep subduction and exhumation) and their mineralogy can preserve a detailed record of chronologic information of these dynamic processes. Here, we present an approach that integrates multiple radiogenic isotope systems in the same sample to provide a more complete timeline for the subduction–collision–exhumation processes, based on eclogites from the Dabie–Sulu orogenic belt in eastern China, one of the largest UHP terranes on Earth. In this study, we integrate garnet Lu–Hf and Sm–Nd ages with zircon and titanite U–Pb ages for three eclogite samples from the Sulu UHP terrane. We combine this age information with Zr‐in‐rutile temperature estimates, and relate these multiple chronometers to different P–T conditions. Two types of rutile, one present as inclusions in garnet and the other in the matrix, record the temperatures of UHP conditions and a hotter stage, subsequent to the peak pressure (‘hot exhumation') respectively. Garnet Lu–Hf ages (c. 238–235 Ma) record the initial prograde growth of garnet, while coupled Sm–Nd ages (c. 219–213 Ma) reflect cooling following hot exhumation. The maximum duration of UHP conditions is constrained by the age difference of these two systems in garnet (c. 235–220 Ma). Complementary zircon and titanite U–Pb ages of c. 235–230 Ma and c. 216–206 Ma provide further constraints on the timing of prograde metamorphism and the ‘cold exhumation' respectively. We demonstrate that timing of various metamorphic stages can thus be determined by employing complementary chronometers from the same samples. These age results, combined with published data from adjacent areas, show lateral diachroneity in the Dabie–Sulu orogeny. Three sub‐blocks are thus defined by progressively younger garnet ages: western Dabie (243–238 Ma), eastern Dabie–northern Sulu (238–235 Ma) and southern Sulu terranes (225–220 Ma), which possibly correlate to different crustal slices in the recently proposed subduction channel model. These observed lateral chronologic variations in a large UHP terrane can possibly be extended to other suture zones. 相似文献
6.
苏鲁地体折返与郯庐断裂活动:莱阳盆地中生界碎屑锆石年代学的制约 总被引：1，自引：0，他引：1
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
7.
《International Geology Review》2012,54(10):906-920
Petrological and isotopic evidence suggests that the protolith of the Sulu ultrahigh-pressure (UHP) terrane was Precambrian continental crust consisting of granite, granodiorite, gabbro, marble, and basic dikes, with local granulite-facies assemblages. Around 220 Ma this unit of continental rocks was buried to depths up of ～120 km within the mantle. Structures formed during exhumation suggest highly mobile behavior of acidic rocks, even under conditions of very low water activity. Petrological studies show that the Sulu terrane underwent isothermal decompression, which implies relatively rapid exhumation, and suggests that the role of melting during exhumation may have been underestimated. The later stages of exhumation are associated with NW-SE-directed tectonic transport and the formation of at least one major normal detachment. 相似文献
8.
A. Vamvaka W. Siebel F. Chen J. Rohrmüller 《International Journal of Earth Sciences》2014,103(1):103-119
Apatite fission-track (AFT) dating applied to uplifted Variscan basement blocks of the Bavarian Forest is employed to unravel the low-temperature history of this segment of the Bohemian Massif. Twenty samples were dated and confined track lengths of four samples were measured. Most samples define Cretaceous APT ages between 110 and 82 Ma (Albian to Campanian) and three samples give older ~148–140 Ma (Jurassic–Cretaceous boundary) ages. No discernible regional age variations exist between the areas north-east and south-west of the Pfahl shear zone, but >500 m post-Jurassic and post-Cretaceous vertical offsets along this and other faults can be inferred from elevation profile analyses. The AFT ages clearly postdate the Variscan exhumation history of the Bavarian Forest. Thermal modeling reveals that the ages are best explained by a slight reheating of the basement rocks to temperatures within the apatite partial annealing zone during the middle and late Jurassic and/or by late Cretaceous marine transgression causing burial heating, which affected marginal low-lying areas of the Bohemian Massif and the Bavarian Forest. Late Jurassic period was followed by enhanced cooling through the 120–60 °C temperature interval during the subsequent exhumation phase for which denudation rates of ~100 m myr?1 were calculated. On a regional scale, Jurassic–Cretaceous AFT ages are ubiquitous in marginal structural blocks of the Bohemian Massif and seem to reflect the exhumation of these zones more distinctly compared to central parts. 相似文献
9.
锆石微区矿物包体的激光拉曼和阴极发光测试以及相应的SHRIMP U-Pb定年结果表明,苏鲁地体片麻岩锆石微区记录了十分复杂的年代学信息。其中副片麻岩锆石核部记录了345～743 Ma的继承性锆石年龄,标志着原岩碎屑锆石来源的复杂性;含柯石英的锆石微区记录了220～234 Ma的超高压变质年龄;而含石英包体的边部则记录了202～219 Ma的退变质年龄。正片麻岩继承性锆石核部所记录的年龄为574～680 Ma,表明原岩锆石曾经历了部分Pb丢失,原岩的形成年龄应大于680 Ma;含柯石英锆石微区所记录的超高压变质年龄为224～242 Ma;而锆石边部所记录的退变质年龄为209～219 Ma。两类片麻岩锆石微区所隐藏的超高压变质和退变质年龄信息十分相近,平均值分别为229±4Ma和211±4Ma,标志着苏鲁地体超高压变质时代应为印支期,相应的构造抬升速率约5.6 km/Ma。该项成果不仅确定了苏鲁地体超高压变质和退变质时代,而且对于深入探讨苏鲁地体快速折返过程中的动力学机制有着重要的科学意义。 相似文献
10.
《International Geology Review》2012,54(15):1887-1908
ABSTRACTThe widespread migmatites in the northwestern part of the Sulu Orogen, China, indicate regional anatexis that is of great significance when discussing the tectonic evolution of this continental orogenic belt. Cathodoluminescence (CL) images, U–Pb ages, and in situ trace element compositions of zircons from four pegmatite veins within these migmatites provide clear evidence for the nature of the post-collisional evolution of the Sulu Orogen. The inherited zircon cores reveal that the protoliths of the migmatites were middle Neoproterozoic magmatic rocks (810–620 Ma) of the South China Block. The protoliths underwent two partial melting events. The mantle domains of the inherited zircons record a Late Triassic (222.0–204.0 Ma) partial melting event that occurred during the exhumation and retrograde metamorphism, after ultrahigh-pressure (UHP) metamorphism. Subsequent newly grown zircons record a Middle–Late Jurassic to Early Cretaceous (164.1–125.5 Ma) anatexis event, indicating that the late Mesozoic anatexis started before ca. 164.1 Ma, reached a peak at ca. 152.1 Ma, and ceased at ca. 125.5 Ma. Combined with previous results of studies on the Sulu orogen, the late Mesozoic anatexis suggested that the thickened crust of the Sulu Orogen had started to become unstable before 164.1 Ma. The duration of ~164.1–137 Ma corresponds to a period of transition in the tectonic regime of the Sulu Orogen, enabling the early high-temperature ductile deformation. After ca. 137 Ma, the tectonic regime was fully transformed into extension and the Sulu Orogen underwent rapid thinning and collapse, thus leading to the late medium–low temperature ductile deformation (137–121 Ma) and laying the foundations for the large-scale magmatic emplacement during the late Early Cretaceous (127–115 Ma). These two partial melting events together promoted the rapid exhumation of the Sulu UHP rocks. 相似文献
11.
The Jiaodong Peninsula is a key region for researching the interaction between the North and South China Plates. Tectonic relationships between collision, exhumation of ultra-high-pressure (UHP) slabs, strike-slip faulting and gold mineralization, are still ambiguous. The eastern part of the Jiaodong Peninsula (Eastern Jiaodong), which includes Triassic intrusions and is less affected by the Tan-Lu Fault Zone, is a key area to examine exhumation dynamics in detail. Systematic field mapping and zircon U–Pb dating of Triassic intrusions establishes that: (1) The UHP wedge in the eastern part of the Jiaodong Peninsula can be divided into the lateral and frontal ramps of a thrust and nappe system. Dating of samples from Donglinghou (244.7 ± 4.2 Ma) and Qingyutan (233.8 ± 8.1 Ma) areas indicates that the collision happened at or before the Middle Triassic. (2) Postcollisional extension intrusions including the Shidao granitoid (216.2 ± 2.4 Ma), and the Chengshantou granitoid (cut by a dolerite dyke dated at 210.5 ± 1.0 Ma), generally strike NE and occurred in a metamorphic core complex below the Upper Jiashan-Xiangshui detachment (U-JSXS). (3) Regional faults in the Jiaodong Peninsula exploited syncollisional foliations of the UHP wedge, which resulted in faults dipping towards the NW and SE. The reactivation of the Lower Jiashan-Xiangshui shear zone (L-JSXS) and its overprinting upon the Tan-Lu fault system may have caused another major episode of exhumation of the syncollisional wedge, and could have been responsible for an extensional environment that favored gold mineralization. 相似文献
12.
B. R. HACKER S. R. WALLIS M. O. MCWILLIAMS P. B. GANS 《Journal of Metamorphic Geology》2009,27(9):827-844
New 40 Ar/39 Ar ages are presented from the giant Sulu ultrahigh-pressure (UHP) terrane and surrounding areas. Combined with U-Pb ages, Sm-Nd ages, Rb-Sr ages, inclusion relationships, and geological relationships, they help define the orogenic events before, during and after the Triassic collision between the Sino–Korean and Yangtze Cratons. In the Qinling microcontinent, tectonism occurred between 2.0 and 1.4 Ga. The UHP metamorphism occurred in the Yangtze Craton between 240 and 222 Ma; its thermal effect on the Qinling microcontinent was limited to partial resetting of K-feldspar 40 Ar/39 Ar ages. Subsequent unroofing at rates of 5–25 km Myr−1 brought the UHP terrane to crustal levels where it underwent a relatively short amphibolite facies metamorphism. The end of that metamorphism is marked by 40 Ar/39 Ar ages in the 219–210 Ma range, implying cooling at crustal depths at rates of 50–200 °C Myr−1 . Ages in the 210–170 Ma range may reflect protracted cooling or partial resetting by Jurassic or Cretaceous magmatism. Jurassic 166–149 Ma plutonism was followed by cooling at rates of c. 15 °C Myr−1 , suggesting relatively deep crustal conditions, whereas Cretaceous 129–118 Ma plutonism was succeeded by cooling at rates of c. 50 C Myr−1 , suggesting relatively shallow crustal depths. 相似文献
13.
Eclogite origin and timings in the North Qinling terrane,and their bearing on the amalgamation of the South and North China Blocks 总被引：3，自引：0，他引：3
H. WANG Y.‐B. WU S. GAO X.‐C. LIU H.‐J. GONG Q.‐L. LI X.‐H. LI H.‐L. YUAN 《Journal of Metamorphic Geology》2011,29(9):1019-1031
The amalgamation of South (SCB) and North China Blocks (NCB) along the Qinling‐Dabie orogenic belt involved several stages of high pressure (HP)‐ultra high pressure (UHP) metamorphism. The new discovery of UHP metamorphic rocks in the North Qinling (NQ) terrane can provide valuable information on this process. However, no precise age for the UHP metamorphism in the NQ terrane has been documented yet, and thus hinders deciphering of the evolution of the whole Qinling‐Dabie‐Sulu orogenic belt. This article reports an integrated study of U–Pb age, trace element, mineral inclusion and Hf isotope composition of zircon from an eclogite, a quartz vein and a schist in the NQ terrane. The zircon cores in the eclogite are characterized by oscillatory zoning or weak zoning, high Th/U and 176Lu/177Hf ratios, pronounced Eu anomalies and steep heavy rare earth element (HREE) patterns. The zircon cores yield an age of 796 ± 13 Ma, which is taken as the protolith formation age of the eclogite, and implies that the NQ terrane may belong to the SCB before it collided with the NCB. The ?Hf(t) values vary from ?11.3 to 3.2 and corresponding two‐stage Hf model ages are 2402 to 1495 Ma, suggesting the protolith was derived from an enriched mantle. In contrast, the metamorphic zircon rims show no zoning or weak zoning, very low Th/U and 176Lu/177Hf ratios, insignificant Eu anomalies and flat HREE patterns. They contain inclusions of garnet, omphacite and phengite, suggesting that the metamorphic zircon formed under eclogite facies metamorphic conditions, and their weighted mean 206Pb/238U age of 485.9 ± 3.8 Ma was interpreted to date the timing of the eclogite facies metamorphism. Zircon in the quartz vein is characterized by perfect euhedral habit, some oscillatory zoning, low Th/U ratios and variable HREE contents. It yields a weighted mean U–Pb age of 480.5 ± 2.5 Ma, which registers the age of fluid activity during exhumation. Zircon in the schist is mostly detrital and U–Pb age peaks at c. 1950 to 1850, 1800 to 1600, 1560 to 1460 and 1400 to 1260 Ma with an oldest grain of 2517 Ma, also suggesting that the NQ terrane may have an affinity to the SCB. Accordingly, the amalgamation between the SCB and the NCB is a multistage process that spans c. 300 Myr, which includes: the formation of the Erlangping intra‐oceanic arc zone onto the NCB before c. 490 Ma, the c. 485 Ma crustal subduction and UHP metamorphism of the NQ terrane, the c. 430 Ma arc‐continent collision and granulite facies metamorphism, the 420 to 400 Ma extension and rifting in relation to the opening of the Palaeo‐Tethyan ocean, the c. 310 Ma HP eclogite facies metamorphism of oceanic crust and associated continental basement, and the final 250 to 220 Ma continental subduction and HP–UHP metamorphism. 相似文献
14.
北苏鲁威海地区超基性岩的原岩形成时代和超高压变质时代 总被引：12，自引：8，他引：4
超基性岩是苏鲁超高压变质地体中一类特殊且十分重要的岩石类型,它们通常呈规模不一的块状、条带状或不规则透镜状 (体) 赋存于区域大面积出露的花岗质片麻岩中。锆石中矿物包体激光拉曼测试、阴极发光图像分析和不同性质锆石LA-ICP-MS U-Pb定年等综合研究结果表明,北苏鲁威海地区含橄榄石辉石岩 (样品W1和W2) 中锆石的成因十分复杂,可进一步划分3种不同类型锆石。其中第一类锆石呈自形-半自形晶,阴极发光图像显示清晰的岩浆结晶环带,矿物包体主要为Ol+Cpx+Ap, 记录的207Pb/206Pb年龄为1835~1845Ma,应代表含橄榄石辉石岩的原岩形成时代;第二类为变质重结晶锆石,呈半自形-他形晶,阴极发光图像显示模糊的岩浆结晶环带,矿物包体与第一类完全一致,记录的206Pb/238U年龄变化范围大,为250~784Ma之间,表明部分继承性岩浆结晶锆石明显受到后期岩浆-变质热事件的影响而发生不完全重结晶和Pb丢失,进而使其记录的年龄相对偏新;第三类锆石呈他形晶,为典型的变质锆石,阴极发光图像十分均匀,矿物包体相对少见,主要为Grt+Cpx,记录的206Pb/238U年龄为230~234Ma, 且与苏鲁地体榴辉岩及其围岩中含柯石英锆石微区记录的超高压变质年龄 (225~235Ma) 十分一致,应代表含橄榄石辉石岩的峰期超高压变质时代。超基性岩中超高压变质锆石的准确识别表明苏鲁地体在峰期超高压变质阶段的确存在流体,流体的存在对超高压变质锆石的形成起着至关重要的作用。该项研究不仅准确厘定北苏鲁威海地区超基性岩的原岩形成时代和超高压变质时代,而且对于深入探讨苏鲁-大别超高压地体流体行为、演化规律及其水-岩相互作用机理具有重要的科学意义。 相似文献
15.
16.
Protolith and metamorphic ages of the Haiyangsuo Complex, eastern China: a non-UHP exotic tectonic slab in the Sulu ultrahigh-pressure terrane 总被引：8，自引：0，他引：8
J. G. Liou T. Tsujimori W. Chu R. Y. Zhang J. L. Wooden 《Mineralogy and Petrology》2006,88(1-2):207-226
Summary The Haiyangsuo Complex in the NE Sulu ultrahigh-pressure (UHP) terrane has discontinuous, coastal exposures of Late Archean
gneiss with amphibolitized granulite, amphibolite, Paleoproterozoic metagabbroic intrusives, and Cretaceous granitic dikes
over an area of about 15 km2. The U–Pb SHRIMP dating of zircons indicates that theprotolith age of a garnet-biotite gneiss is >2500 Ma, whereas the granulite-facie
metamorphism occurred at around 1800 Ma. A gabbroic intrusion was dated at ∼1730 Ma, and the formation of amphibolite-facies
assemblages in both metagabbro and granulite occurred at ∼340–460 Ma. Petrologic and geochronological data indicate that these
various rocks show no evidence of Triassic eclogite-facies metamorphism and Neoproterozoic protolith ages that are characteristics
of Sulu-Dabie HP-UHP rocks, except Neoproterozoic inherited ages from post-collisional Jurassic granitic dikes. Haiyangsuo
retrograde granulites with amphibolite-facies assemblages within the gneiss preserve relict garnet formed during granulite-facies
metamorphism at ∼1.85 Ga. The Paleoproterozoic metamorphic events are almost coeval with gabbroic intrusions. The granulite-bearing
gneiss unit and gabbro-dominated unit of the Haiyangsuo Complex were intruded by thin granitic dikes at about 160 Ma, which
is coeval with post-collisional granitic intrusions in the Sulu terrane. We suggest that the Haiyangsuo Complex may represent
a fragment of the Jiao-Liao-Ji Paleoproterozoic terrane developed at the eastern margin of the Sino-Korean basement, which
was juxtaposed with the Sulu terrane prior to Jurassic granitic activity and regional deformation. 相似文献
17.
Raehee Han Kyoungwon Min Jin-Han Ree David A. Foster 《International Journal of Earth Sciences》2014,103(3):757-776
The Permo–Triassic collision of the North and South China blocks caused the development of the Dabie–Sulu Orogen in China and Songrim Orogen in the Korean Peninsula. Extension after this collision is known from the Dabie–Sulu Orogen, but post-orogenic extension is not well defined in the Korean Peninsula. Extensional deformation along the southern boundary of the Gyeonggi Massif in Korea is characterized by top–down-to-the-south ductile shearing and subsequent brittle normal faulting, and was predated by regional metamorphism and north-vergent contractional deformation. Extension occurred between ~220 and 185 Ma based on the ages of pre-extensional regional metamorphism and post-extensional pluton emplacement. 40Ar/39Ar dating of syn-extensional muscovite in quartz–mica mylonite yields an age of 187.8 ± 5.6 (2σ) Ma, in agreement with constraints from structural relationships. Together with the extensional deformation identified along the northern boundary of the Gyeonggi Massif (~226 Ma), the extension along the southern boundary is probably related to the exhumation of the massif during late-orogenic or post-orogenic extension associated with the Songrim Orogeny of the Korean Peninsula and forms an important event in the Phanerozoic crustal evolution of East Asia. 相似文献
18.
北苏鲁变辉长岩锆石U-Pb年龄和Lu-Hf同位素组成及其对源区的指示 总被引：1，自引：0，他引：1
在北苏鲁经历超高压变质的花岗片麻岩中零星分布着一些变质表壳岩包体或者残片,通常称之为荆山群。北苏鲁荆山群的年代学特征以及构造亲缘性仍不清楚。本文报道了威海市郊和海阳所附近的荆山群露头,有脉状变质辉长岩侵入到荆山群岩系中。对上述两处变质辉长岩中锆石的阴极发光照片、稀土元素配分模式和Th/U比值的综合分析表明,它们均为岩浆锆石,部分岩浆锆石具有弱发光效应和岩浆韵律环带的核部、以及被改造的强发光效应的边部,但未见新生的变质锆石。未被改造的岩浆锆石微区的LA-ICP-MS U-Pb定年结果表明,威海市郊变辉长岩(S4-2)的~(207)Pb/~(206)Pb年龄值变化范围是1831~1966 Ma,加权平均年龄为1870±34 Ma(MSWD=0.6);海阳所变辉长岩(H3)中绝大部分锆石的~(207)Pb/~(206)Pb年龄值变化范围是1769~1887 Ma,加权平均年龄为1839±37 Ma(MSWD=0.5),两件样品共同记录了一致的ca.1.85 Ga岩浆事件。另外,海阳所变辉长岩中3颗捕获的岩浆锆石分别测得ca.2.9 Ga、ca.2.3 Ga和ca.2.1 Ga等三组~(207)Pb/~(206)Pb年龄。两件样品ca.1.85 Ga岩浆锆石具有相似的Hf同位素组成,其ε_(Hf)(t)=-6.1~-10.7,t_(DM2)=2.74~2.98 Ga,捕获ca.2.1 Ga和ca.2.9 Ga锆石的ε_(Hf)(t)值和t_(DM2)年龄分别是-1.9和2.7 Ga、-4.8和3.5 Ga。锆石U-Pb年龄、Lu-Hf同位素特征表明,北苏鲁两处变辉长岩记录的岩浆事件与胶北前寒武纪陆壳的多期演化历史一致,变辉长岩及其围岩荆山群可能是源自胶北的外来地质体。 相似文献
19.
Zoned Zircon from Eclogite Lenses in Marbles from the Dabie-Sulu UHP Terrane, China： A Clear Record of Ultra-deep Subduction and Fast Exhumation 总被引：3，自引：0，他引：3 
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下载免费PDF全文 Liu Fulai 《《地质学报》英文版》2007,81(2):204-225
Eclogite lenses in marbles from the Dabie-Sulu ultrahigh-pressure (UHP) terrane are deeply subducted meta-sedimentary rocks. Zircons in these rocks have been used to constrain the ages of prograde and UHP metamorphism during subduction, and later retrograde metamorphism during exhumation. Inherited (detrital) and metamorphic zircons were distinguished on the basis of transmitted light microscopy, cathodoluminescence (CL) imaging, trace element contents and mineral inclusions. The distribution of mineral inclusions combined with CL imaging of the metamorphic zircon make it possible to relate zircon zones (domains) to different metamorphic stages. Domain 1 consists of rounded, oblong and spindly cores with dark-luminescent images, and contains quartz eclogite facies mineral inclusion assemblages, indicating formation under high-pressure (HP) metamorphic conditions of T = 571-668℃and P = 1.7-2.02 GPa. Domain 2 always surrounds domain 1 or occurs as rounded and spindly cores with white-luminescent images. It contains coesite edogite facies mineral inclusion assemblages, indicating formation under UHP metamorphic conditions of T = 782-849℃and P > 5.5 GPa. Domain 3, with gray-luminescent images, always surrounds domain 2 and occurs as the outermost zircon rim. It is characterized by low-pressure mineral inclusion assemblages, which are related to regional amphibolite facies retrograde metamorphism of T = 600-710℃and P = 0.7-1.2 GPa. The three metamorphic zircon domains have distinct ages; sample H1 from the Dabie terrane yielded SHRIMP ages of 245±4 Ma for domain 1, 235±3 Ma for domain 2 and 215±6 Ma for domain 3, whereas sample H2 from the Sulu terrane yielded similar ages of 244±4 Ma, 233±4 Ma and 214±5 Ma for Domains 1, 2 and 3, respectively. The mean ages of these zones suggest that subduction to UHP depths took place over 10-11 Ma and exhumation of the rocks occurred over a period of 19-20 Ma. Thus, subduction from～55 km to > 160 km deep mantle depth took place at rates of approximately 9.5-10.5 km/Ma and exhumation from depths >160 km to the base of the crust at～30 km occurred at approximately 6.5 km/Ma. We propose a model for these rocks involving deep subduction of continental margin lithosphere followed by ultrafast exhumation driven by buoyancy forces after break-off of the UHP slab deep within the mantle. 相似文献
20.
The Tan–Lu fault is a major strike-slip fault in eastern China that appears to offset the high-grade rocks of the Hong’an–Dabie–Sulu orogen left-laterally ∼540 km. We evaluate models for the collision between the South and North China blocks, published radiometric dates recording HP–UHP metamorphism and exhumation in the Hong’an–Dabie and Sulu terranes, and the timing of sinistral motion on the Tan–Lu fault to evaluate whether UHP rocks provide a piercing point for offset on the Tan–Lu fault. UHP metamorphism in Hong’an–Dabie was concurrent with Sulu based on U–Pb dating of coesite-bearing domains of zircon at 244 ± 5–226 ± 2 Ma for Hong’an–Dabie and 243 ± 4–225 ± 2 Ma for Sulu. Retrograde metamorphism began c. 220 Ma for both Hong’an–Dabie and Sulu, but retrograde zircon growth ended c. 214 Ma in Hong’an–Dabie and continued until c. 202 Ma in Sulu based on U–Pb dating of zircon domains external to coesite-bearing domains. Structures in Sulu are rotated 25° counter-clockwise from, but are broadly similar to, Hong’an–Dabie suggesting the two areas have a common Triassic orogenic history that pre-dates motion on the Tan–Lu fault, and that is consistent with paleomagnetic studies. We constructed a pre-Cretaceous restoration of the Hong’an–Dabie–Sulu belt that moves the Sulu terrane south, aligning the suture and the eclogite-facies isograd, and rotates Sulu c. 25° clockwise to re-align structures with Hong’an–Dabie. Our restoration is supported by published data and shows that the Hong’an–Dabie–Sulu orogen is a piercing point for post-collisional offset on the Tan–Lu fault and that these regions shared a common subduction–exhumation history. The Tan–Lu fault did not play a significant role in the Hong’an–Dabie–Sulu collision and likely developed later, in the Early Cretaceous. 相似文献