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1.
在苏北超高压变质带以南存在一条与之平行的高压变质带。带内由东南向西北可进一步划分出蓝闪石-黑硬绿泥石带,石榴石-绿帘石带和蓝晶石-黄玉带三个变质亚带。从蓝门石-黑硬绿泥石带到蓝晶石-黄玉带变质温压逐渐升高,其峰期地热梯度为15±3℃/km,属于高压变质相系。北侧超高压变质带的典型矿物组合是石榴石+绿辉石+柯石英+金红石,地热梯度为9±2℃/km。高压变质带峰期变质与北侧超高压带峰期变质的地热梯度明显不同,而与超高压变质体的退变质地热梯度相吻合。结合同位素年代学资料,本文指出本区的高压变质作用与北侧的超高压变质作用不是同时发生,而是与超高压变质体的退变质作用同时发生于中生代的印支期。含柯石英榴辉岩的超高压峰期变质早于印支期,并经两次抬升出露于地表。 相似文献
2.
本文应用SHRIMP方法精确测定了金沙江蛇绿岩带中蛇绿岩的辉长岩和斜长岩、呈脉状产于辉长岩和变质橄橄岩中的斜长花岗岩、以及呈岩株状侵入蛇绿岩中的花岗闪长岩的锆石U-Pb年龄,提供了古特提斯洋壳演化的年代学制约。滇西之用层状角闪辉长岩的年龄为328±8Ma,书松斜长岩为329±7Ma,白马雪山辉长岩为282～285Ma,它们可能反映了海底扩张不同阶段的时代。研究还表明,在这些辉长岩和斜长岩中,部分锆石记录了375～352Ma的略老的年龄,暗示蛇绿岩浆活动可能始于晚泥盆世。在金沙江蛇绿岩中,滇西娘九丁斜长花岗岩和川西雪堆斜长花岗岩,具有高硅低钾的成分特征。但是,这些岩石的REE总量高,LREE富集;Sr初始值高,达0.7058～0.7070;在其锆石组成中,存在继承锆石。这些证据表明斜长花岗岩中存在陆壳物质的混染,可能与洋壳俯冲消减有关。娘九丁斜长花岗岩的年龄为285±6Ma,雪堆斜长花岗岩为300±5Ma,记录了古特提斯洋壳俯冲消减事件。滇西吉义独花岗闪长岩,呈岩株状侵入蛇绿岩中,年龄为263±6Ma,限定了蛇绿混杂岩的年代上限。 相似文献
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4.
在26°45′N和25°15′N纬度之间的中Aravalli段,由Delhi超群构成的最新元古宙褶皱带与太古宙BGC区(条带状片麻质杂岩)是一条宽于500m的狭窄剪切带。剪切带中发育有Delhi超群的所有岩石类型。并偶然见到BGC岩片。晚期侵入体的成分与Delhi岩石的成分之间有一些差异。下述薄层条带状组合的出现:方辉橄榄岩,辉石岩、角闪石岩、叶片状蛇纹岩、变质基性岩(斜长角闪岩)、花岗质岩石(包括斜长花岗岩)、晚期橄榄苦橄岩墙,这套组合很类似于很蛇绿岩系。在各种组合中没有真正的高压矿物,但是角闪石岩中黑硬绿泥石,斜长角闪岩或钙硅酸岩中浅色角闪石的存在以及后两组岩石中黝帘石说明了中高压环境。 相似文献
5.
祥山和于埠变质辉长岩是胶北地块上古元古代变质镁铁质岩石的典型代表,辉长岩侵入古元古代荆山群野头组,产有"祥山式"岩浆熔离型铁矿,成矿的专属性指示辉长岩属于层状侵入体类型,形成于大陆伸展构造背景。在祥山变质辉长岩中获得了1851±9Ma的变质年龄,在于埠变质辉长岩中获得了2052±23Ma的锆石U-Pb成岩年龄和1834±5Ma的变质年龄。~2.05Ga的岩浆结晶锆石的εHf(t)值均为正值(+1.87~+3.64),一阶段Hf模式年龄(tDM)为2292~2381Ma(平均为2327Ma),指示于埠变质辉长岩源自古元古代中期的亏损地幔。于埠变质辉长岩的成岩年龄制约了荆山群野头组的沉积上限,荆山群中至少有一部分形成于2.2~2.05Ga之间,沉积于大陆裂谷-稳定大陆边缘的构造环境。祥山和于埠变质辉长岩中有少量斜长花岗岩与之伴生,这些斜长花岗岩具有类似于大洋斜长花岗岩的岩石特征,低K、Ti、Sr,高Na、Yb,形成于低压背景;从斜长花岗岩中获得了1848±8Ma和1873±5Ma的锆石U-Pb年龄,斜长花岗岩中的锆石Th/U比值较低(0.01~0.29),具有初始熔体中结晶锆石特征。结合斜长花岗岩的地球化学特征,推测它们是辉长岩部分熔融的产物,并指示~1.87Ga已由挤压构造体制转变为伸展构造体制。综合前人研究成果,胶北地块已识别出2.18~2.15Ga、~2.10Ga、~2.05Ga的三期双峰式岩浆岩构造组合,指示2.2~2.05Ga期间总体为伸展构造背景。因此建议胶-辽-吉活动带的形成演化过程划分为两个阶段,早期为大陆裂解-稳定陆缘演化阶段(2.2~2.0Ga),沉积了巨量的陆缘碎屑岩-碳酸盐岩建造;晚期为俯冲-碰撞造山阶段(2.0~1.85Ga),胶-辽-吉活动带褶皱造山。 相似文献
6.
山东省胶南地区斜长花岗岩的发现 总被引：8，自引：1，他引：7
胶南地区斜长花岗岩与中元古代变辉长岩相伴产出,由６０％的斜长石和４０％的石英组成。化学成分以高硅,低至中等的铝、低Ｋ２Ｏ为特征,与大洋斜长花岗岩相似,其单颗粒锆石Ｐｂ－Ｐｂ同位素年龄是（１３７０．６±１４．３）Ｍａ。 相似文献
7.
首次报道了扬子克拉通黄陵穹隆北部崆岭杂岩古元古代水月寺混杂岩带中发现特征性石榴石-蓝晶石-硬绿泥石组合低温-高压（LT-HP）榴辉岩相变泥质岩，其变质峰期矿物组合为石榴石+蓝晶石+硬绿泥石+多硅白云母+金红石+石英.相平衡模拟计算得到一条近等温减压的顺时针型变质P-T轨迹，其峰期变质条件为571~576℃，19.2~21.8 kbar.LA-ICP-MS锆石U-Pb年代学研究获得变泥质岩中碎屑锆石核部年龄集中于2.1~2.2 Ga，变质增生边年龄为1 991±20 Ma.Grt-Ky-Cld组合榴辉岩相变泥质岩原岩形成构造环境和变质峰期条件指示，其形成于较低地温梯度（dT/dP≈300℃/GPa）下的活动大陆边缘冷俯冲构造环境，进一步表明至少从古元古代开始具有“冷俯冲”构造特征的现代板块构造体制已经启动. 相似文献
8.
本文对秦岭勉略（勉县—略阳）构造混杂带康县—勉县段的铁镁质岩块或蛇绿岩块进行了系统的锆石SHRIMP UPb年代学研究。测年结果表明，勉略构造混杂带康县—勉县段铁镁质岩块的形成时代为841±16~812±11Ma，蛇绿混杂岩中的辉长岩和辉绿岩块的形成时代为827±14~808±10Ma。从西向东，勉略构造混杂带不同地段蛇绿岩块或铁镁质岩块的锆石UPb同位素年龄在误差范围内相同，表明勉略混杂岩带中的蛇绿岩块所代表的是新元古代古洋壳残片。中部三岔子斜长花岗岩的形成年龄（923Ma±13）大于其他铁镁质岩块和蛇绿岩。 相似文献
9.
赣中变质岩带的组成及构造变质变形特征 总被引：1，自引：0，他引：1
赣中变质岩带不是简单的一套震旦纪地层 ,而是由结晶基底中元古界中深变质岩系 (斜长角闪岩的Sm Nd全岩等时线年龄为 1113± 4 9Ma)和褶皱基底变质较浅的震旦系组成。两者之间以具热流体参与的混合岩化、韧性剪切带和递进变质三位一体组成的动热变质带接触。结晶基底经历了4期构造变质变形的叠加改造 ,每期构造变形都在变质岩石构造单元内留下各种变形形迹 ,变质作用表现为时间上的递进和空间上的叠加演化系列 ,是一套以众多的不平衡结构和多相共生混存的矿物组合 ,热变质带为一套动热变质塑性变形带 ,空间上依次形成绢云母—绿泥石带、黑云母带、石榴石带、十字石带以及夕线石带 相似文献
10.
蛇绿岩及蛇绿岩中浅色岩的SHRIMP U-Pb测年 总被引：101，自引：2，他引：101
文中简要评述了蛇绿岩的层状辉长岩,斜长岩和斜长花岗岩,以橄榄岩为主岩的花岗岩和蛇绿岩中的埃达克岩的锆石SHRIMP U-Pb年龄的地质意义。层状辉长岩(或堆晶层状辉长岩)通常起源于洋脊下的岩浆房,因而它的形成年龄代表洋壳形成的时代。斜长岩与层状辉长岩的时代相近或略晚。斜长花岗岩年龄的解释极其依赖锆石组成和地球化学证据。橄榄岩为主岩的花岗岩,可能记录蛇绿岩的侵位时代。蛇绿岩中的埃达克岩是消减洋壳在深部的部分熔融的产物。文中发表了新疆扎河坝蛇绿岩SHRIMP定年的中间成果,并简略地介绍了滇川西部金沙江和内蒙古图林凯等地的研究实例。根据层状辉长岩的测定结果,扎河坝蛇绿岩形成于(489±4)Ma,金沙江蛇绿岩形成于(328±8)Ma。内蒙古图林凯蛇绿岩中埃达克岩形成于(467±13)Ma～(429±7)Ma。块状辉长岩、斜长花岗岩和橄榄岩为主岩的花岗质岩石记录了蛇绿岩的复杂演化。新疆扎河坝蛇绿岩中的块状辉长岩中存在多组锆石年龄值。较老的一组为468～511 Ma,与层状辉长岩和斜长岩相似,记录了蛇绿岩或洋壳的形成时代,但是,岩石中的大部分锆石年龄为396～419 Ma,加权平均年龄为(406±4)Ma,可能反映了一次部分熔融事件。滇川西部金沙江蛇绿岩中的斜长花岗岩的形成年龄为约300～285Ma,晚于层状辉长岩和? 相似文献
11.
新疆阿尔泰造山带矿床成矿系列 总被引：3，自引：0，他引：3
在系统分析阿尔泰造山带成矿区（带）地质构造演化和成矿特点基础上,划分了４个矿床成矿系列、４个矿床成矿亚系列和６个矿床式。矿床成矿系列和亚系列的形成和分布受区域构造岩浆演化制约。阿尔泰造山带矿床成矿系列具有鲜明的晚古生代成矿作用特点。区域构造演化的规律和后期构造对早期构造的叠加,决定了矿床成矿系列的规律分布和局部复合。 相似文献
12.
The lower valley of Changjiang, from Wuhan of the Hubei Province in the west to Zhenjiang of the Jiangsu Province in the east, contains more than 200 polymetallic (Cu–Fe–Au, Mo, Zn, Pb, Ag) deposits and is one of the most important metallogenic belts in China. This metallogenic belt, situated at the northern margin of the Yangzi craton and bordered by the Dabieshan ultrahigh pressure metamorphic belt to the north, consists mainly of Cambrian–Triassic marine clastic sedimentary rocks and carbonate and evaporite rocks, which overlay a Precambrian basement and are intruded by Yanshanian (205 to 64 Ma) granitoid intrusions and subvolcanic complexes. Repeated tectonism from Late Proterozoic to Triassic resulted in extensively developed networks of faults and folds involving the Cambrian–Triassic sedimentary strata and the Precambrian basement. The Yanshanian granitoid intrusions and subvolcanic complexes in the Lower Changjiang metallogenic belt are characterized by whole-rock δ18O of +8‰ to +10‰, initial 87Sr/86Sr of 0.704 to 0.708, and εNdt from −10 to −17 and have been interpreted to have originated from mixing between juvenile mantle and old crustal materials. Also, the Yanshanian granitoids exhibit eastward younging and increase in alkalinity (i.e., from older calc–alkaline in the west to younger subalkaline–alkaline in the east), which are related to oblique collision between the Yangzi and Sino-Korean cratons and tectonic evolution from early compressional to late extensional or rifting regimes. Most polymetallic deposits in the Lower Changjiang metallogenic belt are clustered in seven districts where the Yanshanian magmatism is particularly extensive: from west to east, Edong, Jiurui, Anqing–Guichi, Luzhong, Tongling, Ningwu and Ningzhen. Mineralization is characterized by the occurrence of three distinct types of orebodies in individual deposits: orebodies in Yanshanian granitoid intrusions, skarn orebodies at the contact zones between the Yanshanian intrusions and Late Paleozoic–Early Mesozoic sedimentary rocks, and stratabound massive sulfide orebodies in the Late Paleozoic–Early Mesozoic sedimentary strata. The most important host sedimentary strata are the Middle Carboniferous Huanglong Formation, Lower Permian and Lower–Middle Triassic carbonate and evaporite rocks. The intrusion-hosted and skarn orebodies exhibit well-developed zonation in alteration assemblages, metal contents, and isotopic compositions within individual deposits, and apparently formed from hydrothermal activities related to the Yanshanian magmatism. The stratabound massive sulfide orebodies in the Late Paleozoic–Early Mesozoic sedimentary strata have long been suggested to have formed from sedimentary or volcano-sedimentary exhalative processes in shallow marine environments. However, extensive research over the last 40 years failed to produce unequivocal evidence for syngenetic mineralization. On the basis of geological relationships and isotope geochemical characteristics, we propose a carbonate-hosted replacement deposit model for the genesis of these stratabound massive sulfide orebodies and associated skarn orebodies. This model suggests that epigenetic mineralization resulted from interactions between magmatic fluids evolved from the Yanshanian intrusions with carbonate and evaporite wall rocks. Mineralization was an integral but distal part of the larger hydrothermal systems that formed the proximal skarn orebodies at the contact zones and the intrusion-hosted orebodies. The stratabound massive sulfide deposits of the Lower Changjiang metallogenic belt share many features with the well-studied, high-temperature, carbonate-hosted replacement deposits of northern Mexico and western United States, particularly with respect to association with small, shallow granitoid complexes, structural and stratigraphic controls on mineralization, alteration assemblages, geometry of orebodies, metal association, metal zonation and isotopic systematics. 相似文献
13.
德尔布干成矿带火山岩型金(铜)矿床地质特征 总被引：4，自引：0，他引：4
近年来 ,在德尔布干成矿带发现了四五牧场金 (铜 )矿床 ,矿床地质特征显示成矿与晚侏罗世—早白垩世火山活动有关 ,今后应注意寻找此类型矿床 相似文献
14.
Geotectonic subdivision and areal extent of the Sangun belt, Inner Zone of Southwest Japan 总被引：8，自引：0，他引：8
Y. NISHIMURA 《Journal of Metamorphic Geology》1998,16(1):129-140
The Sangun belt has long been considered to be a major coherent glaucophanitic terrane of Permian to Triassic age, and to be paired with the low-P/T Hida belt to the north. However, recent progress in geochronology, metamorphic geology, and tectonics has revealed that the belt is in fact comprised of two geologic units of different ages and with contrasting conditions of formation. The older unit is named the Renge belt and the younger the Suo belt. The Renge belt is the oldest of the high-P/T metamorphic belts in the Japanese Islands and extends from northern Kyushu, through the San-in coastal regions, to the Hida marginal belt. It is characterized by 330–280 Ma ages and the association of glaucophane–schist to epidote–amphibolite facies schists. The Renge belt is also typically associated with meta–ophiolite sequences (470–340 Ma) including serpentinite. The Suo belt is characterized by 230–160 Ma high-P/T schists closely related to weakly metamorphosed Permian accretionary rocks of the Akiyoshi belt. Metamorphic facies series is from the prehnite–pumpellyite facies through the pumpellyite–actinolite and glaucophane–schist facies to the epidote–amphibolite facies. The belt is widespread in west Kinki to north and central Kyushu via Chugoku, but also stretches further to the southwest and is present in the Ishigaki-Iriomote Islands of the southern Ryukyu Arc. Throughout this belt, there are scattered small blocks or lenses of meta–ophiolite, whose K–Ar ages of relict hornblendes are 590 to 220 Ma. Bounded by low-angle faults and thrusts, both belts define subhorizontal nappes dipping gently north. The geotectonic framework in the Inner Zone of Southwest Japan is made up of, from north to south, the Hida-Oki, Renge, Akiyoshi, Suo, Maizuru plus ultra-Tamba, Mino-Tamba, and Ryoke belts, with a tectonically downward-younging polarity. This has resulted from stepwise accretions during Palaeozoic to Mesozoic time. 相似文献
15.
The Occidental terrane of the central segment of the Brasiliano-Pan-African Ribeira belt comprises two crustal scale thrust sheets (Andrelândia and Juiz de Fora domains) taken as reworked Neoproterozoic products of the São Francisco cratonic margins. Pre-1.8 Ga orthogneisses and associated rocks of the Mantiqueira Complex comprise the basement for rocks of the Andrelândia Depositional Cycle within the Andrelândia tectonic domain. Geochemical data indicate that the Mantiqueira Complex comprises rocks that can be grouped as follows: intermediate to acid calc-alkaline rocks and a transitional basaltic series. On the basis of quantitative analysis of the lithogeochemical data, these lithotypes cannot be related. Statistical and/or petrological criteria made it possible to define suites and/or groups within each one of those units and to constrain petrogenetic models based mostly on their REE data. Simple least-square regression analysis indicates that the basic rocks are unlikely to constitute a single suite themselves. The results of the geochemical modelling presented in this work suggest that crustal partial melting rather than fractional crystallisation is the most likely petrogenetic process associated with the rocks of the Mantiqueira Complex. The partial melting processes might have taken place under oxidising conditions, typical of tectonic settings associated with the generation of calc-alkaline rocks. 相似文献
16.
新疆东昆仑鸭子泉蛇绿岩的基本特征及其大地构造意义 总被引：19，自引：2，他引：17
鸭子泉蛇绿岩位于新疆东昆仑祁漫塔格山系中部, 与阿尔金断裂平行产出, 由超基性岩、基性岩和拉斑玄武岩等组成。它侵位于早石炭世含放射虫的深海沉积物中, 可能代表了东昆仑祁漫塔格地区晚古生代的板块俯冲带。蛇绿岩可能来源于俯冲带附近的由小型扩张中心形成的次生洋壳, 之后由于消减作用, 侵位到深海沉积物中, 形成了造山带中的蛇绿岩。 相似文献
17.
新疆和静县查岗诺尔铁矿床位于伊犁微板块北缘之博洛科努早古生代岛弧带,属于阿吾拉勒金、铜、铅、锌、铁成矿带东段。矿区出露地层主要为下石炭统大哈拉军山组火山岩和上石炭统伊什基里克组火山岩,两者为断层接触关系。由于成矿矿浆的多期次活动,查岗诺尔铁矿广泛发育围岩蚀变,形成沿断裂带分布的带状蚀变带。通过研究发现,矿床主矿体FeⅠ号主矿体的围岩蚀变情况,按不同蚀变矿物组合,自东向西可分出石榴石带、绿帘石-阳起石带、阳起石-磁铁矿带、蚀变大理岩带和阳起石带,对应三期蚀变作用。各阶段的矿物共生组合分别为：磁铁矿＋透辉石＋石榴石、磁铁矿＋阳起石＋绿帘石、磁铁矿-石榴石-阳起石-绿帘石-石英-碳酸盐。矿区蚀变是由高、中温火山热液交代中酸性火山碎屑岩而形成。 相似文献
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19.
Lin Hefu 《中国地质大学学报(英文版)》1994,(1)
ＥｖｏｌｕｔｉｏｎａｎｄＳｔｒｕｃｔｕｒａｌＳｔｙｌｅｏｆＴｉａｎｓｈａｎａｎｄＡｄｊａｃｅｎｔＢａｓｉｎｓ，ＮｏｒｔｈｗｅｓｔｅｒｎＣｈｉｎａ￥ＬｉｎＨｅｆｕ（ＥｅｐａｒｔｍｅｎｔｏｆＥｎｅｒｇｙＲｅｓｏｕｒｃｅｓＧｅｏｌｏｇｙ，ＣｈｉｎａＵｎｉｖ... 相似文献
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根据金矿产出的地质背景，可将本区金矿分为产于绿岩带的中金矿及产于花岗岩侵入体中的金矿两类，但不论哪类金矿，其成矿物质都主要来自绿岩带，燕山早期重熔花岗岩浆活动为成矿提供了热源及部分矿质，介质，赋矿构造主要为西太平洋板块活动的所产生的ＳＮ向，ＮＥ向，甚至ＮＷ向的断裂或断裂破碎带，成矿期为燕山（早）期。 相似文献