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1.
对西大别造山带夏店岩体进行了系统的锆石LA-ICP-MSU-Pb定年、岩石地球化学研究,发现该岩体化学成分具富硅、碱,贫钙、镁、铝等特点;岩石轻稀土元素富集,重稀土元素亏损,轻重稀土元素分馏明显,Eu亏损明显;Rb、K、Th等大离子亲石元素和Pb元素富集,Ta、Nb、Ti等高场强元素亏损和Sr、Ba元素亏损;岩石成因类型上属于A型花岗岩。LA-ICP-MS锆石U-Pb定年结果显示夏店岩体~(206)Pb/~(238)U加权平均年龄为130.0±1.8 Ma,代表岩体的结晶年龄,显示该岩体为早白垩世岩浆活动的产物。夏店岩体A型花岗岩形成于造山期后环境,预示着桐柏-大别造山带板内演化阶段的到来。 相似文献
2.
五丈山花岗岩是熊耳山地区出露面积居第二位的酸性侵入岩,它的岩石成因及深部动力学过程研究不仅可为熊耳山区域构造演化提供新的证据,而且能为区域内生金属成矿动力学研究提供新的参考,还可为熊耳山地区地质找矿提供新的思路。对五丈山斑状黑云母二长花岗岩样品WZS01进行了LA ICP MS锆石U Pb定年,27个测点中的18个测点的同位素比值位于n(207Pb)/n(235U)—n(206Pb)/n(238U)一致线上,它们的加权平均年龄为159. 6±1. 6 Ma。结合五丈山花岗岩的SHRIMP和LA ICP MS锆石U Pb定年结果,认为它是晚侏罗世约160 Ma岩浆活动的产物。五丈山花岗岩160颗锆石的U Pb年龄形成了一个从新太古代至晚侏罗世的单颗粒锆石年龄谱,8个峰值年龄依次为~2. 8 Ga、~2. 3 Ga、~1. 9 Ga、~1. 8 Ga、~1. 7 Ga、~1. 3 Ga、~178 Ma和~160 Ma,区域上均存在与之对应的岩浆热事件。五丈山花岗岩具有高硅、富碱高钾、贫镁低钙的特征,属于钾玄岩系列和高钾钙碱性系列。它富集大离子亲石元素,亏损高场强元素Nb、Ta,在微量元素蛛网图上显示明显的Nb、Ta、P及Ti负异常,稀土配分模式具有右倾平滑、轻稀土富集及重稀土亏损及无明显负Eu异常等特征。五丈山花岗岩具有高Sr、低Y的特征,属于高锶低钇中酸性岩（Adakite,有人音译为埃达克岩）,它是加厚大陆下地壳的部分熔融形成的,部分熔融源区的残余相矿物包括石榴子石、金红石和角闪石,且无（富钙）斜长石残留。熊耳山地区在~160 Ma经历的岩石圈拆沉作用致使不同深度范围、不同成分的原岩近同时发生部分熔融,多种成因的锆石加入到深部流体内并与之快速上升,途中注入到未完全固结岩浆/流体库,在经历岩浆—流体活化后上侵至地壳浅部后形成了具有复杂单颗粒锆石年龄谱的五丈山花岗岩。另外一方面,深部流体也因熊耳山地区~160 Ma岩石圈拆沉而获得快速释放,其周缘~160 Ma的Au、Mo成矿作用得益于深部含矿流体的有效封闭,五丈山花岗岩周缘及深部仍具有巨大的内生金属成矿潜力。 相似文献
3.
天目山正长花岗岩位于华北克拉通南缘、北秦岭构造带及桐柏—大别造山带构造拼合地区,其岩石成因模型可为秦岭—大别造山带燕山期深部构造演化提供新的限定。它的n(206Pb)/n(238U)加权平均年龄为129. 2±1. 7 Ma,形成于早白垩世。天目山花岗岩锆石稀土元素具有轻稀土亏损、重稀土富集、Ce和Sm正异常及明显Pr、Nd和Eu负异常（δEu值介于0. 01 ~ 0. 19）,锆石的形成温度介于603 ~ 788 ℃之间,天目山锆石/熔体体系中稀土元素分配系数波动特征表明其形成中存在深部岩浆/流体混合作用。天目山花岗岩样品具有富硅、碱和贫钙、镁的特征,在SiO2 —K2O图解中落入高钾钙碱性系列。在微量元素蛛网图中,它们显示了明显的Rb、Th及Zr、Hf的异常峰和Sr、P、Ti的异常谷。它们的稀土总量介于106??10-6~ 139??10-6之间,(La/Yb)N值范围是5. 94 ~ 9. 22,其稀土配分模式具轻稀土富集、中稀土亏损和重稀土略微富集的“V”型（海鸥型）特征,Eu负异常明显（δEu值介于0. 06 ~ 0. 16）。它们的10000Ga/Al值介于3. 38 ~ 4. 15,Nb和Ta的含量分别为63. 5??10-6~ 131??10-6和3. 20??10-6~ 7. 55??10-6（Nb/Ta值介于17. 3 ~ 22. 9）,天目山花岗岩属于A型花岗岩中富Nb的A1亚类。天目山花岗岩部分熔融源区位于角闪岩相,源区残余相主要为角闪石和斜长石且无石榴子石残余。天目山花岗岩形成于板内构造环境,它是早白垩世~130 Ma桐柏山三合店—鸡公山区域岩石圈拆沉作用的岩浆响应,幔源富Nb岩浆/流体因此得以快速释放,上侵途中混合活化壳源岩浆/流体库之后就位固结成岩。 相似文献
4.
豫西崤山小妹河岩体LA-ICP-MS锆石U-Pb定年、地球化学特征及地质意义 总被引：2，自引：1，他引：1
对豫西崤山北部的小妹河岩体中的黑云母石英二长岩进行了LA-ICP-MS锆石U-Pb定年,30个锆石测点中有23个测点的U-Pb同位素测定值位于或接近一致线,年龄值集中于2644~2695Ma、2490~2546Ma、2367Ma、1844~1859Ma、143.6Ma和129.6~133.8Ma 6个年龄段内。最新年龄段内的9个锆石测点206Pb/238U年龄加权平均值为131.5±0.9Ma,代表了小妹河岩体的形成时代。23颗锆石的U–Pb年龄形成了一个新太古代—早白垩世的锆石年龄谱,区域上均存在与之对应的岩浆热事件。小妹河岩体具有富碱、贫镁的特征,属于高钾钙碱性系列;其稀土元素配分模式显示富集轻稀土元素、亏损重稀土元素,(La/Yb)N值为18.36~24.78,无明显Eu异常;微量元素蛛网图显示Nb、Ta槽及P、Ti负异常。小妹河岩体样品高Sr、低Yb及Y,具有埃达克岩属性,是加厚大陆下地壳的部分熔融形成的,部分熔融源区残余相矿物包括石榴子石和金红石。小妹河岩体形成的构造背景为早白垩世岩石圈拆沉作用,由此触发的岩浆(流体)混合作用成就了小妹河岩体的锆石U-Pb年龄谱。小妹河岩体的形成时代与小秦岭-崤山-熊耳山地区早白垩世广泛而强烈的成岩成矿时代接近,岩石圈拆沉作用利于深部含矿流体快速释放,小妹河岩体及其周缘应当具有较大的成矿潜力,应当被视为崤山北部的找矿靶区之一。 相似文献
5.
巴斯克花岗闪长岩位于野马泉岛弧内,本文综合野外地质、岩相学、地球化学以及锆石U-Pb年代学等多学科手段,进而为该地区晚石炭世时期构造背景提供岩浆岩约束。岩石地球化学研究表明,岩体主量元素具有高硅、准铝—弱过铝质、钙碱性的I型花岗岩特征;岩石样品稀土元素总量在83.79×10-6至 125.67×10-6之间,且轻/重稀土之间的比值介于5.32至8.63之间(平均值为7.1),指示轻稀土较重稀土富集。Eu 元素轻度负异常 (δEu=0.69~0.89)。样品富集大离子亲石元素(如K、Rb、Ba),且亏损高场强元素(HFSE,如Nb、Ta和Ti)及P, Nb、Ta负异常明显。岩体锆石206U/238Pb加权平均年龄为301.3±2.5 Ma (MSWD=0.33)和310.7±3.6 Ma (MSWD=0.75),表明岩体形成时代为晚石炭世。综合区域地质特征、岩石地球化学和岩浆源区特征,表明东准噶尔地区晚石炭世(310~301 Ma)处于造山带碰撞后的陆壳伸展构造体制,且岩浆具有壳幔混合和分批熔融、增量生长的特征。 相似文献
6.
位于南祁连化隆地区的鲁满山花岗岩体,岩石类型主体为黑云二长花岗岩。LA-ICP-MS锆石U-Pb定年测得其成岩年龄为(452.9±1.8)Ma,属于加里东期岩浆活动的产物。化学组成上,岩体具有高硅、富碱的特征,属于弱过铝质高钾钙碱性系列。微量和稀土元素组成上,岩体富集大离子亲石元素Rb、U、Th、K和Pb,亏损Ba、Sr、Ta、Nb、P、Ti,具明显轻稀土富集,重稀土亏损特征,显示较强烈的负Eu异常(δEu=0.06~0.55,平均0.31),综合地质地球化学资料指示该岩体应属于高分异的Ⅰ型花岗岩。锆石Hf同位素分析结果显示,岩体的εHf(t)为-7.4~0.1,二阶段模式年龄介于1425~1930 Ma,指示成岩过程中应有亏损地幔组分参与,其壳源源区很可能包括化隆岩群。结合区域构造演化,认为鲁满山花岗岩体形成于柴北缘洋壳与中南祁连陆壳俯冲碰撞的地球动力学背景下,由幔源岩浆与其诱发的地壳物质熔融产生的长英质岩浆在地壳深部混合后再经历分异演化形成。 相似文献
7.
通过对桂北平英花岗质岩体详细的锆石U-Pb年代学、Hf同位素组成及岩石地球化学特征的研究,论证了岩体的形成时代、成因类型、源区性质及其与宝坛锡矿的成矿关系。该岩体中心相-粗粒黑云母花岗岩的锆石LA-MC-ICP-MS U-Pb定年表明,其~(206)Pb/~(238)U加权平均年龄为834.2±5.1 Ma,属新元古代构造岩浆活动的产物。平英花岗岩具有高硅、富碱、强过铝质的特征,岩石富集Cs、Rb、U、Ta而亏损Ba、Sr、Ti等元素。球粒陨石标准化稀土配分曲线呈右倾形和强烈的Eu负异常(Eu/Eu*=0.05~0.31)。花岗岩中锆石的εHf(t)值介于-12.6~-1.6之间,峰值在-4.8~-3.0之间;二阶段模式年龄T_(DM)~C(Hf)在1.83~2.51 Ga之间,峰值在1.9~2.0 Ga之间。这些特征表明平英岩体形成于该区古元古代富硼基底的部分熔融作用,并经历了高度的分异演化过程。桂北九万大山—元宝山地区的新元古代黑云母花岗岩具有良好的锡成矿潜力,是华南多时代花岗岩演化及锡多金属成矿系列的重要组成部分。 相似文献
8.
对蒙古国南戈壁省东部的西南欧玉岩体黑云母花岗岩锆石进行了阴极发光照相,结果显示,其具有明显的振荡环带,为典型的岩浆锆石特征。对22颗锆石进行了LA-MC-ICP-MS U-Pb年龄测定,结果显示,21个测点的~(206)Pb/~(238)U年龄介于334±2~335±2Ma之间,年龄加权平均值为335±1Ma,表明西南欧玉岩体形成于早石炭世。 相似文献
9.
韩沟二长花岗斑岩岩体位于崤山北部,其成因研究不仅可对崤山北部构造演化提供重要约束,而且可为区域找矿提供新思路。对韩沟岩体中黑云母二长花岗斑岩进行了LA-ICP-MS锆石U-Pb定年,20个测点的206Pb/238U年龄为142~147 Ma,加权平均年龄为(145.1±0.7)Ma。韩沟岩体具有高硅、富碱高钾、贫镁低钙的特征,属于富钾钙碱性花岗岩类(KCG)。韩沟岩体的稀土配分模式具有右倾、轻稀土富集及重稀土亏损的特征,(La/Yb)N范围为10.41~11.51,显示弱正Eu异常。韩沟岩体样品富集大离子亲石元素,亏损高场强元素Nb、Ta,在微量元素蛛网图上显示明显的Nb、Ta及Ti负异常。韩沟岩体具有高Sr、低Y和低Yb的特征,属于埃达克岩,Na_2O和K_2O含量表明其为C型埃达克岩。韩沟岩体是加厚大陆下地壳的部分熔融形成的,部分熔融源区的残余相矿物包括石榴石和金红石,且无(富钙)斜长石残留。崤山北部至少经历了~145 Ma和~130 Ma两次规模不等的岩石圈拆沉作用,韩沟岩体为~145Ma规模较小岩石圈拆沉作用的产物。韩沟岩体的形成时代与~145 Ma区域成岩成矿期相接近,在岩石圈拆沉作用这一灾变过程中,必然导致深部流体的大规模活动及其快速释放,表明韩沟岩体周缘及深部应具有较大的Au成矿潜力,其周缘11个Au矿床(点)就是最好的找矿证明。 相似文献
10.
滇西梁河地区钾长花岗岩锆石LA-ICP-MS U-Pb定年及其地质意义 总被引：4，自引：0，他引：4
在详细区域地质调查的基础上,对滇西梁河地区具有代表性的两件钾长花岗岩样品中的锆石进行了阴极发光图像、微区原位LA-ICP-MS微量元素分析和U-Pb定年。结果表明,梁河地区钾长花岗岩锆石显示振荡环带的内部结构,指示其岩浆成因;两件样品的锆石具有较高的Th、U含量,稀土元素总量较高,轻稀土亏损、重稀土富集,明显的的Ce正异常和Eu负异常的稀土配分模式,说明其壳源岩浆锆石特征;两件样品的锆石206Pb/238U加权平均年龄分别是(60.7±0.6)Ma和(115.8±1.0)Ma,属古新世和早白垩世花岗岩。结合区域地质特征,腾冲地块在中生代晚期-新生代早期发生多期岩浆作用,揭示滇西三江地区特提斯演化的岩浆响应,为青藏高原东缘地区地质演化的动力过程提供约束。 相似文献
11.
S. Viswanathan K. Surya Prakash Rao B. Mahabaleswar 《Journal of the Geological Society of India》2013,82(6):621-627
Komatiites are mantle-derived ultramafic volcanic rocks. Komatiites have been discovered in several States of India, notably in Karnataka. Studies on the distribution of trace-elements in the komatiites of India are very few. This paper proposes a simple, accurate, precise, rapid, and non-destructive wavelength-dispersive x-ray fluorescence (WDXRF) spectrometric technique for determining Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, Pb, and Th in komatiites, and discusses the accuracy, precision, limits of detection, x-ray spectral-line interferences, inter-element effects, speed, advantages, and limitations of the technique. The accuracy of the technique is excellent (within 3%) for Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Zr, Nb, Ba, Pb, and Th and very good (within 4%) for Y. The precision is also excellent (within 3%) for Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, Pb, and Th. The limits of detection are: 1 ppm for Sc and V; 2 ppm for Cr, Co, and Ni; 3 ppm for Cu, Zn, Rb, and Sr; 4 ppm for Y and Zr; 6 ppm for Nb; 10 ppm for Ba; 13 ppm for Pb; and 14 ppm for Th. The time taken for determining Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, Pb, and Th in a batch of 24 samples of komatiites, for a replication of four analyses per sample, by one operator, using a manual WDXRF spectrometer, is only 60 hours. 相似文献
12.
13.
奥地利安东帕有限公司 《岩矿测试》2009,28(3):306-306
最新的流行病学研究表明,空气中较高浓度的悬浮细颗粒可能对人类的健康有不利的影响。根据该项研究显示,由于心脏病、慢性呼吸问题和肺功能指标恶化而导致死亡率的升高与细尘粒子有关。这些研究结果已经促使欧盟于1999年4月出台了限制空气中二氧化硫、二氧化氮、氧化氮、铅和颗粒物含量的法案(1999/30/EC),对各项指标包括对可吸入PM10颗粒的浓度提出了新的限制性指标。PM10颗粒是指可以通过预分级器分离采集的气体动力学直径小于10μm的细颗粒。目前研究的兴趣重点逐步偏向PM2.5这些更细微颗粒物,PM2.5这种颗粒物对健康有明显的不利影响。在欧盟指令2008/50/EC中,对PM10和PM2.5都提 相似文献
14.
E. M. Prasolov S. A. Sergeev B. V. Belyatsky E. S. Bogomolov K. A. Gruzdov I. N. Kapitonov R. Sh. Krymsky V. O. Khalenev 《Geochemistry International》2018,56(1):46-64
This paper reports the first results of a study of 11 isotope systems (3He/4He, 40Ar/36Ar, 34S/32S, 65Cu/63Cu, 62Ni/60Ni, 87Sr/86Sr, 143Nd/144Nd, 206–208Pb/204Pb, Hf–Nd, U–Pb, and Re–Os) in the rocks and ores of the Cu–Ni–PGE deposits of the Norilsk ore district. Almost all the results were obtained at the Center of Isotopic Research of the Karpinskii All-Russia Research Institute of Geology. The use of a number of independent genetic isotopic signatures and comprehensive isotopic knowledge provided a methodic basis for the interpretation of approximately 5000 isotopic analyses of various elements. The presence of materials from two sources, crust and mantle, was detected in the composition of the rocks and ores. The contribution of the crustal source is especially significant in the paleofluids (gas–liquid microinclusions) of the ore-forming medium. Crustal solutions were probably a transport medium during ore formation. Air argon is dominant in the ores, which indicates a connection between the paleofluids and the atmosphere. This suggests intense groundwater circulation during the crystallization of ore minerals. The age of the rocks and ores of the Norilsk deposits was determined. The stage of orebody formation is restricted to a narrow age interval of 250 ± 10 Ma. An isotopic criterion was proposed for the ore-bearing potential of mafic intrusions in the Norilsk–Taimyr region. It includes several interrelated isotopic ratios of various elements: He, Ar, S, and others. 相似文献
15.
Mining induced subsidence can significantly affect mining costs where major surface facilities and natural environment need to be protected. Overburden grout injection is a technology used to control coal mine subsidence by injecting the mine waste material extracted from the coal back into the inter-burden rock during longwall mining. The flowing slurry is here categorised as a nonlinear viscous cohesive (Bingham plastic) fluid. During longwall mining the grout slurry is pumped into the separated beds of the rock mass through a central vertical borehole, which is drilled deep into the inter-burden rock strata above the coal seam. However, a blockage can occur in the injection system when the slurry velocity falls below a certain critical threshold velocity, indicating a material phase change from cohesive-viscous to cohesive-frictional. In situ field injection tests through boreholes have been simulated at a smaller scale at the CSIRO laboratory in Brisbane by pumping the slurry through a radial disk (gap = 4 mm) from its centre. Laboratory experiments indicate a general, nonlinear, cohesive, viscous, frictional model for shear behaviour of the slurry, in which the material shear parameters are functions of the disk radial distance. Complete dimensional and dimensionless analytical solutions have been developed based on an approach related to Bingham–Herschel–Bulkley fluid mechanics. The derived formulae include relations for minimum pump pressure, local pressure and pressure gradient, wall shear stress, volume rate, velocity and velocity gradient. The theoretical results match the experimental measurements. The experiments covered slurries with maximum particle sizes of 0.5 to 2 mm with about 50% being larger than 100 µm. The viscosities at the various solids concentrations were measured with a standard torsion viscometer. This study differs from the previous research in several distinct aspects, namely, consideration of the variable shear parameters rather than fixed values, inclusion of total nonlinear behaviour, and implementation of a friction function to mimic behaviour of the deposited and consolidating stiff slurry, which can cause a significant pressure rise as a result of the increased shear resistance. 相似文献
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17.
Alexander E. C. Broberg J. S. Kehren A. R. Graziani M. M. Turri W. L. 《Environmental Geology》1993,22(4):353-361
Bellechester, Minnesota, is a small community of approximately 155 residents located on the county line between Goodhue and Wabasha counties in southeast Minnesota's karst region. Bellechester is served by a 21-year-old wastewater treatment facility (WWTF) consisting of three waste-stabilization ponds. On 28 April 1992 six sinkholes were discovered to have drained cell 2 of the WWTF resulting in the loss of approximately 8.7×106 1 of partially treated effluent and about 600 m3 of soil into previously undetected subsurface voids of unknown dimensions. In the week following the collapse, approximately 200 water wells located within a 5-km radius of the WWTF were sampled in an after-the-fact, emergency sampling program. Twelve samples with elevated fecal coliform levels, 18 samples with nitrate-nitrogen greater than the 10 mg/1 standard, and no samples with elevated chlorides were found. However, the elevated levels could not be unambiguously attributed to the WWTF collapse. This is the third WWTF to fail by sinkhole collapse in southeast Minnesota since 1974. All three collapsed lagoons have been located in similar geomorphic and stratigraphic settings. However, at least two lagoons have collapsed in the adjacent area in northeast Iowa, and these lagoons are located at different stratigraphic positions. Twenty-two WWTFs constructed in southeast Minnesota's karst region in the last 25 years have been identified as subject to potential sinkhole collapse. An unknown but significant number of manure storage lagoons, flood control structures, etc., have also been constructed in the karst region and are at risk. Public agencies are beginning to develop plans to deal with the risk associated with existing and future waste lagoons in this environment. The critical hydrogeologic parameters that can be used to prioritize the risk of collapse at existing facilities include: (1) the lithology of the first bedrock beneath each lagoon, (2) the thickness of surficial materials between the lagoon and the bedrock surface, (3) the presence and construction of liners (seepage rate), and (4) the proximity to existing sinkholes. 相似文献
18.
Mercury,arsenic, antimony,and selenium contents of sediment from the Kuskokwim River,Bethel, Alaska,USA 总被引：1，自引：0，他引：1
The Kuskokwim River at Bethel, Alaska, drains a major mercury-antimony metallogenic province in its upper reaches and tributaries. Bethel (population 4000) is situated on the Kuskokwim floodplain and also draws its water supply from wells located in river-deposited sediment. A boring through overbank and floodplain sediment has provided material to establish a baseline datum for sediment-hosted heavy metals. Mercury (total), arsenic, antimony, and selenium contents were determined; aluminum was also determined and used as normalizing factor. The contents of the heavy metals were relatively constant with depth and do not reflect any potential enrichment from upstream contaminant sources. 相似文献
19.
滇东南锡、银、铅、锌多金属矿床主要分布在个旧、白牛厂、都龙3个矿区,而滇东南较大的3个花岗岩体又分别出露在3个矿区或附近.花岗岩体均形成于燕山晚期,岩石化学、矿物成分相似,富含锡、银、铅、锌、钨、铜等成矿元素.矿床主金属元素组合与岩体之间的距离由远而近出现由锡、钨、(铍、铌、钽)→锡、钨、(铁)、铜、铟→锡、铅、锌、银、铟、(锑)有规律的变化.花岗岩浆是成矿物质来源和成矿热源.岩浆侵入初期使上覆地层隆起产生背斜(凹陷部位成向斜);同时使地层产生一系列裂隙、压性断层或层间断裂;岩浆侵入晚期,这些断层再次活动,表现为张性,岩浆产生的含矿热液沿由其活动所造成的断裂迁移、充填、交代、沉淀而形成矿床. 相似文献
20.
岩石密度和超高压岩石折返速率 总被引：1，自引：3，他引：1
在常温常压条件下对中国大陆科学钻CCSD主孔100-3000米岩心样品进行了密度测量,建立了密度连续剖面,并界定了不同超高压岩石的密度值。通过对比高温高压物性实验资料,岩石密度随着退变程度增强而降低,榴辉岩密度变化序列为3.52g/cm3→3.49g/cm3→3.07g/cm3→2.93g/cm3。超高压长英质岩石密度变化序列为3.00g/cm→2.80g/cm3→2.65g/cm3。上述实验资料是讨论不同折返阶段岩石所受浮力的基础,为研究折返速率大小提供了基本参数。本文通过折返板块运动平衡时,上浮力与粘滞力平衡这一关系式,定量研究了大陆俯冲板块的折返速率,认为密度差产生上浮力从而引起折返,温度对板块折返速率的影响最为显著;密度差大小、折返角度、折返板块大小对折返速率也有直接的影响。定量模拟分析表明,在温度高于850℃时,板块的折返速率可以超过100mm/a;当温度降至700℃时,折返速率则低于1.5mm/a。作者认为在折返早期,温度较高,板块快速折返至60-70km榴辉岩相深度;随着传导散热,温度降低,板块以较慢的速率折返至中下地壳。折返速率的估算表明,浮力是板块折返第一阶段(从>100km深部折返至<40km的中下地壳)的主要驱动力。 相似文献