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1.
地壳放射性生热效应对大陆俯冲过程影响的数值模拟研究 总被引：1，自引：0，他引：1
岩体中的放射性生热是地幔对流和地壳变质作用的关键热源之一,但地壳放射性生热率是如何影响大陆俯冲-碰撞的动力学过程,尤其是大陆碰撞区域的热结构演化,尚未获得共识。本文使用热-力学数值模拟方法对上、下地壳放射性生热率进行系统的模拟实验,以研究其对大陆俯冲动力学演化过程的影响。模型实验表明,由于大陆上地壳富集U、Th和K等主要放射性生热元素,且放射性生热率的变化区间较大(1.0~3.0μW/m~3),导致其对大陆俯冲碰撞动力学演化过程的影响较为显著,主要包括进入俯冲通道内的上地壳体积大小、碰撞区域内地壳熔融范围、俯冲下地壳物质折返的规模和两大陆的耦合程度等四个方面。而大陆下地壳则以中-基性岩为主,相对亏损U、Th、K等主要放射性生热元素,且放射性生热率的变化区域较小(0.2~0.8μW/m~3),致使其对大陆俯冲演化过程的影响相对有限,主要通过控制俯冲下地壳以及大陆板片的粘滞度和流变强度的大小,进而制约大陆俯冲过程下地壳物质折返的规模以及板片倾角的大小。 相似文献
2.
Wang Yang 《Frontiers of Earth Science》2007,1(1):69-79
Based on the results of a study of regional element abundance in eastern China and the 1:200 000 geochemical surveys in northern
Xinjiang, the element geochemical characteristics of the exposed crust in 23 tectonic units of the continent of China are
summarized. Compared with the global average abundance of the upper continental crust, the exposed crust of the continent
of China is compositionally more evolved than the upper crust of the island arc, but less evolved than the mature Precambrian
Canadian shield. The exposed crust of the North China and Yangtze platforms has a lower SiO2 content, but markedly higher CaO and MgO contents due to the presence of widespread carbonate strata, which suggests that
we should not neglect the contribution of carbonate rocks in the study of the exposed crust and the element abundance of the
upper crust. In comparison with two recently published average compositional models of the global upper continental crust,
the exposed crust of the continent of China is depleted in Au, Hg, Mo, Sn, and W, which suggests that their abundance in the
present global models is overestimated. The exposed crust of the North China platform and the Qinling-Dabieshan fold belt
to its south has lower μ(238U/204Pb) values (<8), but other regions of the continent of China exhibit much higher μ values, which implies that the low μ feature of the North China platform and its adjacent regions does not have global significance. Considering the apparent
lateral variation in composition of the exposed crust for the tectonic units of the continent of China, there is no adequate
reason to take the average upper crust compositional model of the North China platform and its adjacent regions as a reliable
composition representative for Chinese and global upper continental crust composition.
Translated from Geological Bulletin of China, 2005, 24(10–11): 906–915 [译自: 地质通报] 相似文献
3.
《International Geology Review》2012,54(9):1051-1071
Asia is the world’s largest but youngest continent, in which Pacific-type (P-type) and collision-type (C-type) orogenic belts coexist with numerous amalgamated continental blocks. P-type orogens represent major sites of continental growth through tonalite-trondhjemite-granodiorite type (TTG-type) juvenile granitoid magmatism and accretion of oceanic crust and intra-oceanic arcs. The Asian continent includes several P-type orogenic belts, of which the largest are the Central Asian and Western Pacific. The Central Asian Orogenic Belt is dominated by P-type fossil orogens arranged with a regular northward subduction polarity. The Western Pacific is characterized by ongoing P-type orogeny related to the westward subduction of the Pacific plate. Asia has a multi-cratonic structure and its post-Palaeozoic history has witnessed amalgamation of the Laurasia composite continent and Pangaea supercontinent. Nowadays, Asia is surrounded by double-sided subduction zones, which generate new TTG-type crust and supply oceanic crust and microcontinents to its active margins. The TTG-crust can be tectonically eroded and subducted down to the mantle transition zone to form a ‘second’ continent, which may generate mantle upwelling, plumes, and extensive intra-plate volcanism. Moreover, recent plate movements around Asia are dominated by northward directions, which resulted in the India–Eurasia and Arabia–Eurasia collisions beginning at 50–45 and 23–20 Ma, respectively, and will result in Africa–Eurasia collision in the near future. Therefore, Asia is the best candidate to serve as the nucleus for a future supercontinent ‘Amasia’, likely to form 200–250 Ma in the future. In this paper we unravel a puzzle of continental growth in Asia through P-type orogeny by discussing its tectonic history and geological structure, subduction polarity in P-type orogens, tectonic erosion of TTG-type crust and arc subduction at convergent margins, generation of mantle plumes, and prospects of Asia growth and overgrowth. 相似文献
4.
We report new estimates of abundances of rarely analyzed elements (As, B, Be, Bi, Cd, Ge, In, Mo, Sb, Sn, Te, Tl, W) in the upper continental crust based on precise ICP-MS analyses of well-characterized upper crustal samples (shales, pelites, loess, graywackes, granitoids and their composites) from Australia, China, Europe, New Zealand and North American. Obtaining a better understanding of the upper crustal abundance and associated uncertainties of these elements is important in placing better constraints on bulk crust composition and, from that, whole Earth models of element cycling and crust generation. We also present revised abundance estimates of some more commonly analyzed trace elements (Li, Cr, Ni, and Tm) that vary by > 20% compared to previous estimates. The new estimates are mainly based on significant (r2 > 0.6) inter-element correlations observed in clastic sediments and sedimentary rocks, which yield upper continental crust elemental ratios that are used in conjunction with well-determined abundances for certain key elements to place constraints on the concentrations of the rarely analyzed elements. Using the well-established upper crustal abundances of La (31 ppm), Th (10.5 ppm), Al2O3 (15.40%), K2O (2.80%) and Fe2O3 (5.92%), these ratios lead to revised upper crustal abundances of B = 47 ppm, Bi = 0.23 ppm, Cr = 73 ppm, Li = 41 ppm, Ni = 34 ppm, Sb = 0.075, Te = 0.027 ppm, Tl = 0.53 ppm and W = 1.4 ppm. No significant correlations exist between Mo and Cd and other elements in the clastic sediments and sedimentary rocks, probably due to their enrichment in organic carbon. We thus calculate abundances of these elements by assuming the upper continental crust consists of 65% granitoid rocks plus 35% clastic sedimentary rocks. The validity of this approach is supported by the similarity of SiO2, Al2O3, La and Th abundances calculated in this way with their upper crustal abundances given in Rudnick and Gao [Rudnick, R., Gao, S., 2003. Composition of the continental crust. In: Rudnick, R.L. (Ed.), The Crust. In: Holland, H.D., Turekian, K.K. (Eds.), Treatise on Geochemistry, vol. 3. Elsevier–Pergamon, Oxford, pp. 1–64.]. The upper crustal abundances thus obtained are Mo = 0.6 ppm and Cd = 0.06 ppm. Our data also suggest a 20% increase of the Tm, Yb and Lu abundances reported in Rudnick and Gao [Rudnick, R., Gao, S., 2003. Composition of the continental crust. In: Rudnick, R.L. (Ed.), The Crust. In: Holland, H.D., Turekian, K.K. (Eds.), Treatise on Geochemistry, vol. 3. Elsevier–Pergamon, Oxford, pp. 1–64.]. 相似文献
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7.
Determination of the Neoproterozoic Shicaogou Syn-collisional Granite in the Eastern Qinling Mountains and Its Geological Implications 总被引：5，自引：1，他引：4
CHEN Danling LIU Liang SUN Yong ZHANG An ZHANG Chengli LIU Xiaoming LUO JinhaiKey Laboratory of Continental Dynamics Ministry of Education Department of Geology Northwest University Xi''an Shaanxi 《《地质学报》英文版》2004,78(1):73-82
The Shicaogou granite has been identified as a magnesian (Fe-number=0.71-0.76), calcic to calc-alkalic (MALI=3.84-5.76) and peraluminous (ASI=1.06-1.13) granite of the syn-collisional S-type, with high SiO2(>71%), A12O3 (>13%) and Na2O+K2O (6.28%-7.33%, equal for NaO2 and K2O). Trace element and REE analyses show that the granite is rich in LILE such as of Rb, Sr, Ba and Th, and poor in HFSE like Yb, Y, Zr and Hf. Its Rb/Sr ratio is greater than 1; the contents of Nb and Ta, and the ratio of Nb/Ta as well as the REE geochemical features (e.g. REE abundance, visible fractionation of LREE and HREE and medium to pronounced negative Eu anomalies) are all similar to those of crust-origin, continent-continent syn-collisional granite. Moreover, the granite exhibits almost the same pattern as that of the typical continent-continent syn-collisional granite on the spider diagram and all samples fall within the syn-collisional granite field.The cathodoluminescence (CL) investigations have revealed that the zircon f 相似文献
8.
《Journal of South American Earth Sciences》2000,13(3):255-273
Trace element and isotopic compositions of mid-Tertiary siliceous magma sequences from two localities of the Sierra Madre Occidental, northern Mexico, display differences that reflect the composition and age of the basement through which they erupted. The crust beneath the section at San Buenaventura is thicker and more evolved and forms part of the North American basement, while that under El Divisadero consists of allochthonous terranes of island arc/oceanic? crust accreted during the Mesozoic.The volcanics are highly differentiated and range in composition from basalt to rhyolite (SiO2=50–76%). Those erupted through the accreted terranes display a small range of isotope ratios and have lowest initial (age-corrected) Sr isotope ratios (>0.7044) and the highest Nd (<0.5126) and Pb isotope ratios (206Pb/204Pb ∼18.9). Isotope ratios of the continental suite are more variable and form an array which trends away from that of the accreted terrane suite toward compositions more typical of old crust (to 87Sr/86Sr ∼0.710 and 143Nd/144Nd ∼0.5123). The volcanics in the continental zone are relatively more enriched in moderately incompatible elements compared with those within the accreted terranes (Ce/Yb=25–45 vs. 13–33, respectively), but are depleted in some highly incompatible elements such as U and Rb (e.g., Th/U=3.8–7.5 vs. 2.5–4.0, respectively). Those higher in the stratigraphic sections have higher 87Sr/86Sr, 208Pb/204Pb, and Th/U ratios, and lower 143Nd/144Nd ratios than those lower in the sections.The data have implications for the nature of the sources and the petrogenesis of these volcanics. The isotope ratios of both suites fall between those of mafic magma compositions from the Sierra Madre Occidental, and intermediate and felsic lower crustal xenoliths in northern Mexico and the southwestern USA. The relationship between the isotope ratios of the sequences and the age of the basement, combined with the fact that the overall data set forms well-defined isotopic arrays, demonstrates the strong effects of the crust on the chemistry of the silicic magmas. In the continental suite, isotope ratios covary with Th/Pb and U/Pb ratios, approaching the compositions found in the intermediate and felsic granulite facies xenoliths, strongly indicating that they are not anatectic melts of the lower crust but rather reflect interaction between mantle-derived basaltic parental magmas and the crust. Crustal contributions appear to be large, on the order of 20–70%. The small range of isotope ratios in the accreted terrane suite appears to reflect interaction of the basaltic parent with relatively juvenile crust whose isotopic composition is similar to the mantle-derived magmas. High Th/U and Th/Rb ratios indicate that the crustal contamination occurs in the lower crust. Moreover, the less radiogenic 206Pb/204Pb and 207Pb/204Pb ratios in the continental suite indicate that the depletion in highly incompatible elements in the continental lower crust is an old feature. The secular changes in the isotope ratios within the stratigraphic sections indicate increasingly shallow crustal contributions with time, initially by predominantly mafic deep lower crust and later by more felsic middle crust. Using lavas from outside of the two heavily sampled stratigraphic sections, the differences in the isotopic compositions between volcanics erupted through the accreted terranes and the continental basement help to delineate the location of the boundary. 相似文献
9.
《Gondwana Research》2013,24(4):1402-1428
The formation of collisional orogens is a prominent feature in convergent plate margins. It is generally a complex process involving multistage tectonism of compression and extension due to continental subduction and collision. The Paleozoic convergence between the South China Block (SCB) and the North China Block (NCB) is associated with a series of tectonic processes such as oceanic subduction, terrane accretion and continental collision, resulting in the Qinling–Tongbai–Hong'an–Dabie–Sulu orogenic belt. While the arc–continent collision orogeny is significant during the Paleozoic in the Qinling–Tongbai–Hong'an orogens of central China, the continent–continent collision orogeny is prominent during the early Mesozoic in the Dabie–Sulu orogens of east-central China. This article presents an overview of regional geology, geochronology and geochemistry for the composite orogenic belt. The Qinling–Tongbai–Hong'an orogens exhibit the early Paleozoic HP–UHP metamorphism, the Carboniferous HP metamorphism and the Paleozoic arc-type magmatism, but the three tectonothermal events are absent in the Dabie–Sulu orogens. The Triassic UHP metamorphism is prominent in the Dabie–Sulu orogens, but it is absent in the Qinling–Tongbai orogens. The Hong'an orogen records both the HP and UHP metamorphism of Triassic age, and collided continental margins contain both the juvenile and ancient crustal rocks. So do in the Qinling and Tongbai orogens. In contrast, only ancient crustal rocks were involved in the UHP metamorphism in the Dabie–Sulu orogenic belt, without involvement of the juvenile arc crust. On the other hand, the deformed and low-grade metamorphosed accretionary wedge was developed on the passive continental margin during subduction in the late Permian to early Triassic along the northern margin of the Dabie–Sulu orogenic belt, and it was developed on the passive oceanic margin during subduction in the early Paleozoic along the northern margin of the Qinling orogen.Three episodes of arc–continent collision are suggested to occur during the Paleozoic continental convergence between the SCB and NCB. The first episode of arc–continent collision is caused by northward subduction of the North Qinling unit beneath the Erlangping unit, resulting in UHP metamorphism at ca. 480–490 Ma and the accretion of the North Qinling unit to the NCB. The second episode of arc–continent collision is caused by northward subduction of the Prototethyan oceanic crust beneath an Andes-type continental arc, leading to granulite-facies metamorphism at ca. 420–430 Ma and the accretion of the Shangdan arc terrane to the NCB and reworking of the North Qinling, Erlangping and Kuanping units. The third episode of arc–continent collision is caused by northward subduction of the Paleotethyan oceanic crust, resulting in the HP eclogite-facies metamorphism at ca. 310 Ma in the Hong'an orogen and low-P metamorphism in the Qinling–Tongbai orogens as well as crustal accretion to the NCB. The closure of backarc basins is also associated with the arc–continent collision processes, with the possible cause for granulite-facies metamorphism. The massive continental subduction of the SCB beneath the NCB took place in the Triassic with the final continent–continent collision and UHP metamorphism at ca. 225–240 Ma. Therefore, the Qinling–Tongbai–Hong'an–Dabie–Sulu orogenic belt records the development of plate tectonics from oceanic subduction and arc-type magmatism to arc–continent and continent–continent collision. 相似文献
10.
Closure and opening of oceans on time‐scales of a few hundred million years is a fundamental tectonic process on Earth, typically referred to as a “Wilson cycle”. Subduction of oceanic and continental crust leading up to and during continent–continent collision can refertilize and enrich the orogenic continental lithospheric mantle in heat‐producing elements. The resulting thermal anomaly weakens the lithosphere and, along with structural weaknesses (e.g. sutures), make this orogenic lithosphere more prone to rifting given an extensional stress field. Thermal modelling shows that anomalously hot lithosphere can focus asthenospheric upwellings over time‐scales of a few hundred million years. Processes related to closure of oceans thus provide a mechanism for later localization of rifting and an extensional driving force. 相似文献
11.
《China Geology》2018,1(2):236-256
The continent of China is grouped into Pan–Cathaysian blocks, Laurasia and Gondwana Continental margins and relics of three oceans-Paleoasian, Tethys, and Pacific as a whole. In detail, the continent of China grew up by coalescence of three blocks or platforms (North China, Tarim and Yangtze) and eight orogenic belts (Altay–Inner Mongolia–Daxinganling, Tianshan–Junggar–Beishan, Qinling–Qilian– Kunlun, Qiangtang–Sanjiang, Gangdisê, Himalaya, Cathaysia, Eastern Taiwan) during the processes of oceanic crust disappearance and acceretionary-collision of continental crusts. In the orogenic belts, six convergent crustal consumption zones (Ertix–Xar Moron, South Tianshan, Kuanping–Foziling, Bangong co–Shuanghu–Nujiang–Changning–Menglian, Yarlung–Tsangpo, Jiangshao–Chenzhou–Qinfang) have been distinguished. Correspondingly, the strata of the continent of China are subdivided into 17 tectonic-strata superregions, which tectonically belong to three blocks or platforms, six convergent crustal consumption zones and eight orogenic series, respectively. This division is based mainly on differences of tectonic environment and tectonic evolution among blocks, zones and belts, including the timing of when the oceanic crusts transferred into continental crusts, the paleobiogeographic features, and the types of strata. 相似文献
12.
中国大陆地壳和岩石圈化学成分模型可信吗? ——来自大地热流值的检验 总被引：3，自引：0，他引：3
大地热流值是大陆地壳和岩石圈U，Th,K丰度的直接约束；根据地球化学元素丰度值推算出的大地构造单元的区域地壳热流值，必定不能大于区域的平均热流值，根据700余个实测大地热流数据，对目前发表的中国大陆地壳和岩石圈的化学成分模型进行了检验，结果表明，多数模型不能满足大地热充约束，如黎彤等的关于中国大陆及其内部构造单元的地壳和岩石圈成分模型，倪守斌等提出的新疆北部地壳生热率模型，以及高山等提出的扬子地台北缘地壳成分模型，这些模型的U，Th,K丰度值不太可靠，其他强不相容元素的丰度值的可信程度亦值得怀疑，而迟清华，鄢明才提出的华北地台地壳成分模型和高山等建立的中国东部及华北地台和秦岭造山带的地壳成分模型通过了区域大地热流的检验。 相似文献
13.
Mobilization and migration of the heat‐producing elements (HPE) during anatexis is a critical process in the development of orogenic systems, the evolution of continental crust and the stabilization of cratons. In many crustal rocks the accessory minerals are the dominant hosts of Th and U, and the behaviour of these minerals during partial melting controls the concentrations of these elements in draining melt and residue. We use phase equilibrium modelling to evaluate if loss of melt saturated in the essential structural constituents of the accessory minerals can explain the concentrations of Th and U in residual metasedimentary migmatites and granulites along two well‐characterized crustal transects in the Ivrea zone, Italy and at Mt Stafford, Australia. While an equilibrium model of accessory mineral breakdown and melt loss approximates the depletion of U in the residual crust along both transects, it does not explain the relative enrichment of Th. We propose that the high Th concentrations in residual crust may be explained by either inhibition of monazite dissolution by kinetic factors or near‐peak growth of new high Th grains and overgrowth rims on undissolved monazite due to migration of melt through the orogenic crust. Retention of the HPE in the middle and deep orogenic crust may allow metasedimentary granulites to overcome the enthalpy barrier of melting to achieve ultrahigh temperature conditions and may be partly responsible for the slow cooling of many granulite terranes. Lastly, although the mantle was warmer and crustal heat production was higher in the past, peak temperatures and apparent thermal gradients of high‐temperature (HT)–ultrahigh temperature (UHT) granulite terranes have not decreased significantly since the Neoarchean. However, the pressure of HP granulite facies metamorphism has increased gradually from the Archean to the Phanerozoic, which suggests that the lithosphere became stronger as secular cooling of the mantle enabled plate collisions to form thicker orogens. Thus, as the lithosphere became stronger, the proportion of HT–UHT metamorphism associated with thin lithosphere and mantle heat has decreased, whereas the proportion associated with the formation of thick crust and radiogenic heat has increased. 相似文献
14.
东昆仑造山带早古生代经历了完整的洋壳形成、俯冲消减、陆- 陆碰撞造山和造山后垮塌演变过程,目前对陆- 陆初始碰撞时间及碰撞时限还存在较大争议。周缘前陆盆地启动引发的沉积环境突变或不整合形成时间是用来约束大陆初始碰撞时间最直接和最有效的方法之一。本文以东昆仑水泥厂地区角度不整合覆盖于石灰厂组之上的志留纪周缘前陆盆地沉积哈拉巴依沟组为研究对象,开展火山岩夹层锆石U- Pb年代学研究,为约束早古生代陆- 陆初始碰撞时间与碰撞造山时限提供沉积记录证据。结果表明,水泥厂东和雪水河东哈拉巴依沟组下部流纹质凝灰岩锆石U- Pb年龄分别为443. 0±3. 9 Ma和441. 8±1. 3 Ma,结合已报道的石灰厂组火山岩锆石U- Pb年龄（450. 4±4. 3 Ma）,可以确定东昆仑陆- 陆初始碰撞发生在450~443 Ma之间。综合区域上古生代岩浆活动、变质作用、构造变形与相关沉积记录证据,认为东昆仑地区至少从450 Ma左右开始进入陆壳深俯冲及陆- 陆碰撞阶段,在425 Ma左右进入碰撞后伸展阶段,碰撞造山作用至少持续了25 Ma。 相似文献
15.
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
16.
东亚陆缘扩张带──一条离散式大陆边缘成因的探讨 总被引：19，自引：11，他引：19
陈国达 《大地构造与成矿学》1997,21(4):285-293
亚洲东部大陆边缘，介于大陆与大洋之间，存在着一条巨型的“沟弧盆”地带。该构造带的出现是亚洲大陆岩石圈演化－运动史上的重大事件之一，它的成因问题流行假说颇多，本文侧重从亚洲东部壳体演化运动历史背景的分析入手，探讨该构造带形成时期的历史动力环境，地壳结构及性质、壳体演化过程的特点，以及壳体增生扩展过程等，阐明了它是由于东亚陆缘扩张所成。并探讨了该陆线扩张带的形成与壳体演化运动的关系及其扩张机因。研究表明：亚洲陆缘扩张带的形成机理，并非“洋壳俯冲、弧后引张”所致。它们主要是陆缘壳体上的大陆类型活动区（华夏地洼型造山带），在其发展的余动期，由于陆缘扩张及陆壳薄化所致。作者认为，从壳体大地构造学这一新思路入手，对该陆缘扩张带成因的深入研究，有助于正确认识该大陆架上广泛分布的有色、稀有金属内生矿床，以及泥炭、褐煤、油气田的构造类型、特点、分布规律及其经济价值。 相似文献
17.
根据阿尔泰地区1：20万化探均匀采集的1100余个岩石样品的分析结果，基于全样本统计和迭代剔除方法，得到新疆阿尔泰地区表壳(出露地壳)的39种元素丰度值；同时对其中的SiO：、Tio：、A12O3等10种常量元素，按氧化物之和为100％进行了归算。阿尔泰地区表壳在化学成分上相当于花岗闪长岩。与全球大陆上地壳元素丰度值相比，明显富集。MnO、P205和As、Li元素，略富集SiO2和Sb元素，亏损CaO、Na2O和Pb、U以及相容元素Co、Cr、Ni等。阿尔泰地区表壳的K/La、K／Na、K／Th等元素比值与全球大陆上地壳相应元素比值相当；而La／As比值低于全球大陆上地壳，Th／Pb、Th/U、La／Cr比值高于全球大陆上地壳。阿尔泰表壳在成分特征上较典型的岛弧造山带上地壳更为成熟。加里东期、海西期岛弧造山作用以及海西期后的成岩成矿事件是影响和制约阿尔泰表壳元素地球化学特征的重要地质因素。 相似文献
18.
中国陆壳演化、多块体拼合造山与特色成矿的关系 总被引：5，自引：10，他引：5
矿产资源的种类、时空分布、形成演化与成岩作用和大地构造格局密切相关。中国地质构造复杂,成矿条件多样(发育裂谷成矿、碰撞成矿、地幔柱成矿、低温成矿等特色成矿系统),矿床类型比较齐全,如大宗矿产(铁、铝、铜、钾盐)短缺,小宗矿产中盛产稀土元素(REE)、钨、锡、钼矿。中国早前寒武纪矿床相对较少,燕山期成矿集中爆发。这种矿产资源分布格局与中国大陆地壳的性质与演化、多块体拼合造山格局之间的内在联系尚待深入揭示。本文基于对中国陆壳演化、陆块与造山带组成格局和多块体拼合造山的系统分析总结,试图阐明中国成矿特色与其内在联系,从陆壳形成与造山带演化的宏观视角来研究中国大陆成矿特色、成矿物质时空分布规律,其特色包括:(1)中国陆壳的地台区与造山带区质量比约3∶7(全球陆壳地台区占69.6%),太古界面积小且支离破碎,地壳固化时间晚且运动频繁强烈,因此难以形成巨型条带状铁建造(BIF)富铁矿床、太古代火山岩块状硫化物型(VMS)铜锌矿带和元古代内克拉通裂谷有关的扎伊尔-赞比亚巨型铜矿。(2)环绕中朝-塔里木和扬子板块的增生造山带由老到新依次形成,并镶接于古板块边缘,使中国大陆逐渐增生扩展,导致火山岩型、与岩浆岩类和沉积岩系有关的大型矿床空间上向板块边缘推移,时间上越来越新,地壳演化成矿作用和矿床类型越来越多样化。(3)中亚成矿域以古生代多陆块拼合造山、中新生代陆内造山与山盆体系构成独特的地质构造格局。既发育增生造山阶段的弧环境相关矿床(蛇绿岩型铬铁矿、斑岩铜矿、VMS),也发育与碰撞造山有关的矿床(造山型金矿、石棉、滑石、白云母)、地幔柱叠置造山带背景下的岩浆铜镍矿和后碰撞陆内岩石圈伸展相关的大陆环境矿床(斑岩钼矿、热液金矿、伟晶岩型稀有金属矿)。(4)青藏高原(特提斯成矿域)系特提斯洋长期增生演化、印度-欧亚大陆碰撞的产物。其成矿条件优越,具有多期成矿作用、多矿种和多类型的复合成矿系统特点。形成了蛇绿岩套型铬铁矿、密西西比河谷型(MVT)铅锌矿和独具特色的碰撞环境超大型斑岩铜钼矿。(5)我国东部环太平洋成矿域,伴随晚中生代克拉通性质的根本转变及岩石圈明显的减薄过程与破坏,在华北克拉通周缘发生大规模的岩浆活动和强烈的金、铜、钼和轻稀土等成矿作用。不同时期的造山带干涉叠加使得南岭地区盛产花岗岩有关的钨、锡、钼矿,具有叠加改造成矿、大器晚成的鲜明成矿特色。由于中国成矿特色与大陆地壳演化密切相关,中国的找矿勘探部署必须立足于中国大陆演化与多块体拼合造山的基本地质事实,方能取得好的勘查效果。中国大陆小陆块拼合造山成矿还存在诸多未解之谜,文末提出了当前成矿学面临的一系列科学问题,对于今后我国找矿战略选区具有借鉴意义。 相似文献
19.
Quantitative Expression of Heat Flow versus Tectonic Deformation in the China Continent： The Effects of Plastic-Flow Network and Stable Block 总被引：1，自引：0，他引：1
WANG Sheng-zu Institute of Geology State Key Laboratory of Earthquake Dynamics China Earthquake Administration Beijing 《《地质学报》英文版》2006,80(1):97-109
1 Introduction It has been understood in the study of terrestrial heat flow that the distribution of heat flow in the interior of continent is influenced by a large number of factors, involving heat sources (e.g. mantle heat flow, heat production of radioactive elements in the crust, magmatic activity, and heat production of tectonic deformation), heat transfercondition (e.g. thermal conductivity and thickness of media), groundwater circulation, etc. On the background of these factors it is pa… 相似文献
20.
The Himalaya and Lhasa blocks act as the main belt of convergence and collision between the Indian and Eurasian plates. Their crustal structures can be used to understand the dynamic process of continent–continent collision. Herein, we present a 3D crustal density model beneath these two tectonic blocks constrained by a review of all available active seismic and passive seismological results on the velocity structure of crust and lower lithosphere. From our final crustal density model, we infer that the present subduction-angle of the Indian plate is small, but presents some variations along the west–east extension of the orogenic belt: The dip angle of the Moho interface is about 8–9° in the eastern and western part of the orogenic belt, and about 16° in the central part. Integrating crustal P-wave velocity distribution from wide-angle seismic profiling, geothermal data and our crustal density model, we infer a crustal composition model, which is composed of an upper crust with granite–granodiorite and granite gneiss beneath the Lhasa block; biotite gneiss and phyllite beneath the Himalaya, a middle crust with granulite facies and possible pelitic gneisses, and a lower crust with gabbro–norite–troctolite and mafic granulite beneath the Lhasa block. Our density structure (<3.2 g/cm3) and composition (no fitting to eclogite) in the lower crust do not be favor to the speculation of ecologitized lower crust beneath Himalaya and the southern of Lhasa block. 相似文献