共查询到19条相似文献，搜索用时 171 毫秒
1.
二叠纪是地球演化历史进程中的重要一环,并在我国华南地区中二叠统茅口组（孤峰组）地层中普遍沉积一套层状硅质岩,它们可能与中、晚二叠世系列重大地质事件之间有着密切的成因联系。笔者等以位于扬子地块西南缘的贵州纳雍营盘茅口组硅质岩作为研究对象,通过对硅质岩元素地球化学组成进行研究发现,硅质岩Al/(A1＋Fe＋Mn）值以及多项成因判别图解等指示其形成过程中有明显的热水物质输入,具有热水成因硅质岩的特征。结合区域古地理特征,以及硅质岩Ce/Ce*、(La/Ce）N值等综合分析,认为硅质岩形成于黔中台沟内的深水环境。综合考虑区域范围内中二叠世硅质岩研究成果,并分析纳雍营盘硅质岩与峨眉山玄武岩空间关系及峨眉地幔柱活动历史,认为峨眉地幔柱早期海底火山活动可能对包括营盘在内的华南地区中二叠世晚期硅质岩沉积具有重要控制作用。 相似文献
2.
一个热水沉积锑矿床——以贵州晴隆大厂锑矿床为例 总被引：2，自引：1，他引：1
笔者通过对晴隆大厂锑矿床实地调查研究,不仅发现辉锑矿在"大厂层"岩石压实、固结成岩阶段结晶低温热水沉积成因的直接标志,而且还对"大厂层"空间分布、垂向结构、组成特征、矿化阶段、形成环境和成矿时间等进行了初步研究,认为该矿床是中二叠世末期峨眉地幔柱活动早期局限海湾浅水环境低温热水域成岩成矿作用叠加而形成的热水沉积型锑矿床. 相似文献
3.
地幔柱构造的沉积及环境响应——以峨眉地幔柱为例 总被引：3，自引：1，他引：2
通过对上扬子板块西北部中二叠统地层、岩性、古生物及地球化学特征,并结合前人研究资料分析认为,受峨眉地幔柱活动而形成的穹窿状地壳隆升影响,四川盆地中二叠世地貌特征表现为西南部较高,向东及东北方向平缓降低,其中不发育陡斜坡及斜坡转折带。该古地貌特征与区域海平面升降共同控制和影响了研究区古地理格局及演化,形成了受峨眉地幔柱活动控制的缓坡型碳酸盐岩台地。中二叠世岩性、古生物及地球化学特征对峨眉地幔柱活动均有相应的响应,根据穹窿状水下隆起不同部位沉积的岩性、古生物组合、沉积构造以及地球化学特征,四川盆地中二叠世总体表现为西南部环境开阔,水体动荡,发育开阔台地亚相,向东及北东方向逐渐过渡为浅缓坡亚相和深缓坡亚相发育区。开阔台地及浅缓坡环境中生物最为丰富,古串珠虫(Palaeotextularia)组合和翁格达藻(Ungdarella)组合分布于开阔台地,而浅缓坡环境的代表主要为米齐藻(Mizzia)-假蠕孔藻(Pseudovermoporella)组合、球旋虫(Glomospira)-始毛盘虫(Eolasiodiscus)组合及节房虫(Nodosarinae)组合等,向东及东北方向生物逐渐减少,至深缓坡环境,仅在其上部有少量分布。微量元素的丰度变化也反映了古环境特征,从开阔台地至深缓坡,沉积环境逐渐从氧化向还原环境变化,Ba、Sr、V、Cu等微量元素的平均丰度值逐渐增大。 相似文献
4.
通过1：50 000区域地质调查,发现云南省会泽县一带灯影组中普遍发育硅质岩。本文通过硅质岩岩石学特征和地球化学特征分析,重点探讨了灯影组各段硅质岩的成因机制和沉积环境。结果表明：震旦系-寒武系灯影组下段硅质岩中相对富集Al和Ti,总稀土（ΣREE）相对较高,Ce呈负异常,Eu呈正异常;中段硅质岩中相对富集Ca和Mg,总稀土较低,LREE>HREE,Ce呈负异常,Eu呈正异常;上段硅质岩总稀土较低,LREE>HREE,Ce大部分呈负异常,Eu呈正负异常。综合硅质岩岩石学、地球化学特征,并结合震旦纪区域地质构造演化,认为研究区内下段硅质岩表现为正常海水沉积、中段硅质岩表现为典型热水沉积、上段表现出正常海水沉积受热水沉积影响的特征。硅质岩形成于复杂大陆边缘的浅海陆棚环境。 相似文献
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6.
《吉林大学学报(地球科学版)》2015,(Z1)
川东南地区中二叠统茅口组发育结核状、条带状的硅质岩,研究该区的硅质岩成因对川东南茅口组沉积古环境的还原有着重要意义。研究区位于四川盆地东南,属于上扬子地台中部。在研究区内选取北东—南西走向七跃山断裂两侧的武隆江口、石柱打风坳、彭水庞溪等茅口组剖面作为研究对象,通过对武隆江口、石柱打风坳、彭水庞溪三个发育硅质岩的茅口组剖面进行野外剖面实测采样、室内薄片观察和地球化学主量元素、稀土元素分析发现,Al-Fe-Mn三角图解显示武隆剖面硅质岩表现为热液、生物双重成因的影响,石柱和彭水剖面显示主要受到生物成因的影响,经过δCe、Y/Ho值和Fe2O3/Ti O2-Al2O3/(Al2O3+Fe2O3)、LaN/CeN-Al2O3/(Al2O3+Fe2O3)图解等地化分析,认为武隆江口的茅口组硅质岩主要为热液来源,夹杂了少量陆源影响,硅质岩的成因机理以热液成因为主,交代成因和生物成因为辅;石柱和彭水的茅口组硅质岩是以生物为主要来源的生物成因硅质岩,同时部分样品表现出具有少量热液影响的特点。武隆和彭水硅质岩形成于离岸较近的大陆边缘环境,石柱的硅质岩形成于离岸较远的台盆或台洼环境。结合上扬子地区中二叠世沉积环境,推测峨眉山玄武岩是该区热液硅质的主要来源,经过同生断裂(七跃山断裂)运移至川东南地区海底与海水混合成为硅质的主要物源。 相似文献
7.
滇东南麻栗坡位于右江盆地西南缘,该处蛇绿岩被认为是古特提斯洋壳的遗迹,对蛇绿岩所代表八布洋的研究是全面了解右江盆地与华南西南缘古特提斯构造演化的重要环节。研究区广泛发育一套夹有硅质岩的深水相沉积,对麻栗坡八布和西牛堡中—下二叠统他披组硅质岩的地球化学特征研究表明:硅质岩Al/(Al+Fe+Mn)值为0.43~0.70,Al2O3/TiO2值为25.5~44.8,Eu/Eu*值为0.81~1.02,为非热液成因硅质岩。硅质岩Ce/Ce*值分别为0.67~1.29和0.77~1.18,Y/Ho值分别为28.84~31.23和26.41~28.91,形成于大陆边缘环境。结合其他地区硅质岩地球化学特征,认为早—中二叠世八布洋盆的西南缘可能为活动大陆边缘,其洋壳的俯冲方向为南西向。 相似文献
8.
东吴运动性质的厘定及其时空演变规律 总被引：16，自引：0，他引：16
东吴运动是华南地区二叠纪影响较大的一次地壳运动, 然而对其涵义、起始时间、构造界面位置、影响范围和运动属性等方面一直存在争议.通过对上扬子茅口组对比、不整合面特征和岩浆活动等方面的研究, 结合对华南地区二叠纪的地层、沉积及岩相古地理等综合分析, 对东吴运动的性质、地球动力学背景和时空演变规律进行了探讨.认为茅口末期峨眉山地幔柱上升引起的地壳抬升、峨眉山玄武岩的喷发和东吴运动这三者之间存在成因联系; 上扬子中晚二叠世之间的东吴运动是峨眉山地幔柱上升所造成的地壳快速差异抬升.东吴运动具有明显的时空演变规律, 空间上西强东弱、南强北弱, 时间上西早东晚、南早北晚.下扬子及华南地块可能不存在东吴运动, 其中晚二叠世的沉积作用主要受华夏古陆控制. 相似文献
9.
通过对安徽泾县-宣州地区中二叠统"嵇亭岭砾岩"中硅质岩、含角砾硅质岩和硅质角砾岩的岩石学和沉积地球化学分析,认为"嵇亭岭砾岩"为非构造成因异常沉积岩;相当于栖霞组本部灰岩段中上部-顶部灰岩段,时代为中二叠世祥播阶;为热水沉积硅质岩,距离热液通道的远近决定了其产出形态,距离越近,角砾越发育;中二叠世深部岩浆房上涌造成强烈的拉张断陷,形成了穹状隆起和一系列地堑与地垒构造,存在部分上涌的岩浆沿着地堑与地垒的断裂上涌,漫溢至海底乃至地表,上涌的岩浆与海水混合,使海水中硅质含量大幅度升高,发生一系列与热液相关的硅化作用和碳酸盐中硅的置换作用。 相似文献
10.
广西来宾蓬莱滩剖面中上二叠统硅质岩的地球化学特征及沉积背景 总被引：1，自引：0，他引：1
广西来宾地区中上二叠统广泛发育硅质岩,蓬莱滩剖面和铁桥剖面是本地区中上二叠统出露最好的剖面.本文对蓬莱滩剖面28件硅质岩(分别为中二叠统茅口组3件与上二叠统合山组25件)的主量和稀土元素进行了分析研究,并结合岩石学特征,认为:蓬莱滩剖面合山组硅质岩沉积于受到陆源物质影响的边缘海盆环境,它们的硅质主要来源于硅质生物,为生物成因;而其茅口组硅质岩则沉积于远离陆源物质影响的边缘海盆环境,它们的硅质主要来源于热液,为热液成因.通过与铁桥剖面的热液成因硅质岩的沉积背景对比研究,结果表明:中晚二叠世时期,来宾地区为富硅的边缘海盆环境,而陆源物质输入程度的差异是造成本地区形成不同成因硅质岩的主要因素. 相似文献
11.
F.Q. Zhang H.L. Chen X. Yu C.W. Dong S.F. Yang Y.M. Pang G.E. Batt 《Gondwana Research》2011,19(1):163-176
The Songliao Basin is characterized by episodic rifting and intense volcanism during its early development, and forms a key concealed part of the Late Mesozoic magmatic province of NE China. Few precise geochronological and geochemical data were previously available for the volcanic elements of this basin, restricting understanding of its geodynamic setting and evolution. We present new SHRIMP U–Pb zircon ages and geochemical data for the volcanic rocks from the northern Songliao Basin, which limit this volcanism to the Early Cretaceous period (115–109 Ma). Although dominated by rhyolite, the rocks cover a wide compositional spectrum encompassing trachyandesite, basaltic trachyandesite, trachyte and dacite. This suite exhibits a range of geochemical signatures characteristic of subduction-related genesis, falling into a high-K calc-alkaline series, with enrichment in large ion lithophile elements (LILE) and light rare earth elements (LREE), and weak depletion in high field strength elements (HFSE) and heavy rare earth elements (HREE). The suite also shares a common isotopic composition, consistent with derivation from partial melting of a single depleted mantle source. This Early Cretaceous volcanism occurred in an extensional back-arc setting associated with the subduction of the Paleo-Pacific plate, large scale upwelling of the asthenosphere, and intensive lithospheric thinning of the eastern continental margin of NE China which may have lasted until ca. 109 Ma. 相似文献
12.
华南地区印支期经历了强烈的构造运动和岩浆活动,印支期花岗岩的构造背景一直是地学界讨论的热点问题。本文对广西云开地区那蓬黑云母二长花岗岩体进行了详细的锆石年代学、地球化学特征及成因研究。结果显示：那蓬岩体LA-ICP-MS锆石U-Pb年龄加权平均值为（257.8 ±1.2） Ma,结晶年龄为晚二叠世;岩石主量元素具有富钾、富铝质特点,属于钙碱性岩石;微量元素主要富集大离子亲石元素（Rb、Th、U、K、Pb）,亏损高场强元素（Nb、Ta、Ti、Zr、Hf）和Ba、Sr元素;稀土元素特征表现为轻稀土元素相对富集,重稀土元素亏损,稀土元素球粒陨石配分曲线呈右倾型,具有较明显轻重稀土分馏特征和负铕异常（δEu=0.41~0.66）。地球化学特征指示了花岗岩的物质来源主要为古老地壳杂砂-泥质源岩部分熔融,构造环境有可能形成于板块碰撞环境的后造山阶段。 相似文献
13.
攀枝花二叠纪火山岩发育有玄武岩和粗面岩的基性和碱性两个端元,区域上明显缺失中间过渡类型。玄武岩SiO_2含量处于45.65%~49.32%范围内,粗面岩SiO_2含量介于64.39%~69.17%之间,构成经典的"双峰式"火山岩特征组合。两者均具有富Na、贫K、轻稀土富集、轻重稀土明显分馏的特征。特征微量元素Nb/Ta、Th/Ta、Th/U比值变化相对较小,玄武岩分别为15.16、2.70和4.13,粗面岩分别为15.40、2.55和4.12,显示两者具有相似的地球化学属性。微量元素特征显示,除了Ti和Y等少数高场强元素不协调以外,玄武岩与粗面岩绝大多数微量元素变化规律相似,且Rb、Ce、Y、Nb、Hf、Ta等元素与洋岛玄武岩(OIB)特征一致,说明它们具有地幔柱构造系统下的岩浆属性,岩浆源于石榴石二辉橄榄岩岩石圈地幔的部分熔融。结合前人资料,攀枝花二叠纪双峰式火山岩的厘定,不仅暗示了岩浆形成于拉张的裂谷构造环境,也为西南地区二叠纪峨眉山大火成岩地幔柱成因提供支撑。 相似文献
14.
黔西北上二叠统宣威组底部富铌多金属层地球化学特征研究 总被引：1，自引：0，他引：1
黔西北地区峨眉山玄武岩之上、宣威组之下广泛发育一套富铌铝土质黏土岩层,Nb含量最高可达571×10-6,但长期以来对铌富集的原因和形成机理研究较少。本文对威宁玉龙铌矿区富铌层位开展了矿物学和元素地球化学研究,结果表明,富铌铝土质黏土岩与下伏峨眉山玄武岩的Nb—Ta、Zr—Hf具有明显的相关性,两者的稀土元素球粒陨石标准化配分模式图也极为相似,均表现明显的右倾,暗示富铌铝土质黏土岩很可能为峨眉山高钛玄武岩风化的产物。元素质量平衡计算显示,峨眉山玄武岩向富铌铝土质黏土岩过渡,Nb、Zr、Al明显富集,REE等元素则相对贫化。矿物学观察表明,锐钛矿很可能是富铌铝土质黏土岩中Nb的重要载体矿物,锐钛矿风化后会引起Nb的明显富集。综合各项研究,认为峨眉山玄武岩的风化是形成富铌铝土质黏土岩的关键,富铌矿物榍石、锐钛矿等经表生风化很可能是引起铝土质黏土岩中Nb明显富集的重要途径。 相似文献
15.
Satoru Haraguchi Teruaki Ishii Jun-Ichi Kimura 《Contributions to Mineralogy and Petrology》2008,155(5):593-618
Analysis of middle and upper Eocene rocks from the IBM forearc, including the Ogasawara and Mariana Islands, help illuminate
early arc volcanism of the proto-IBM arc. Dredged volcanic rocks from the forearc are two-pyroxene basalt to andesite, and
may be divided into two groups, tholeiite and calc-alkaline, on the basis of mineralogy, petrography, and bulk chemistry.
Tholeiites are characterized by high HFSE contents, high crystallization temperatures, and low water contents. In contrast,
the calc-alkaline rocks are characterized by low HFSE contents, low crystallization temperatures, and higher water contents.
These characteristics indicate that magma genesis for the two series differed. The tholeiites resulted from high degrees of
partial melting of slightly depleted mantle under anhydrous conditions, whereas the calc-alkaline rocks were generated by
low degrees of melting of depleted mantle under hydrous conditions. We believe that differences in mantle depletion arose
from compositional layering and fluid zonations caused by MORB volcanism and slab dehydration, respectively.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
16.
赣西袁水坳陷卡林型金矿床稀土元素地球化学的研究 总被引：1，自引：0，他引：1
赣西卡林型金矿床各类岩矿石的稀土元素地球化学特征的研究表明,与卡林型金矿成矿有关的岩浆岩,其成因是过渡型地壳同熔型成因系列。成矿物质源于容矿围岩及基底地层,部分成矿物质源于下二叠统茅口组,属海底喷流沉积成因。 相似文献
17.
Khromykh S. V. Semenova D. V. Kotler P. D. Gurova A. V. Mikheev E. I. Perfilova A. A. 《Geotectonics》2020,54(4):510-528
Studies of volcanic rocks in orogenic troughs of Eastern Kazakhstan were carried out. The troughs were formed at late-orogenic stages of evolution of Hercynian Altai collision system. Volcanic rocks are represented by basalts, andesites, dacites and rhyolites. Based on geochemical and isotopic data, the basalts and andesites derived from mafic magmas that formed as a result of partial melting of garnet peridotites in the upper mantle under the orogen. U–Pb zircon data prove two volcanic stages: more-scaled Middle Carboniferous (~311 Ma) and less-scaled Early Permian (297–290 Ma). Basalts and andesites in lower parts of the orogenic troughs and independent dacite-rhyolite structures were formed at the Middle Carboniferous stage. Parental mafic magmas were formed as a result of partial melting of mantle substrates in local transtensional zones along large shear faults. The formation of dacites and rhyolites could have been caused by partial melting of crustal substrates under effect of mafic magmas. Transtensional movements in the lithosphere of orogenic belts may indicate the beginning of collapse of orogens. A smaller volume of basalts and andesites formed at the Early Permian stage. Geochemical data prove the independent episode of partial melting in upper mantle. Synchronous basalts and andesites also appeared at wide territory in Tian Shan, Central Kazakhstan, and Central and Southern Mongolia. Early Permian volcanism indicates general extension of the lithosphere at the postorogenic stages. Large-scaled Early Permian mafic and granitoid magmatism in Central Asia has been interpreted in recent years as the Tarim Large Igneous Province caused by Tarim mantle plume activity. Thus, the extension of the lithosphere and associated volcanism in the Early Permian can be an indicator of the onset of the plume–lithosphere interaction process.
相似文献18.
In the stratigraphic sequence of volcanic rocks in the Eastern Sikhote Alin, Maestrichtian-Danian predominantly andesitic volcanics are characterized by a boundary position between the Late Cretaceous subduction, mostly acid volcanic rocks and Cenozoic post-subduction basaltoids. Data on these rocks are important for elucidating the genesis of andesitic magmas, constraining and specifying the geodynamic evolutionary stages in this territory, and revealing the conditions under which the parental melts of these rocks were derived and evolved. Results of detailed mineralogical and geochemical studies, including ICP-MS analysis for trace elements point to a hybrid character of the andesitic volcanic rocks and an important role of fractional crystallization and crustal contamination in their genesis. Although geological evidence (variations in the style of volcanism, the composition of its products, and the character of their distribution) testifies to a change in the geodynamic environment in the Eastern Sikhote Alin in the Maestrichtian-Danian, geochemically the volcanics of this age range are typical subduction-related rocks with anomalously low concentrations of Nb and high contents of K, Ba, Rb, Pb, and U. The volcanic piles contain no adakites, which are indicators of the geodynamic environment in which slab windows are formed. The inconsistency between geological and geochemical indicators of the geodynamic environment suggests certain genetic features of the transitional magmatic series. The parental magmas of the andesitic volcanics were derived from the suprasubduction mantle wedge, which had been metasomatically recycled in the course of the dehydration and melting of the subducted oceanic slab. The increasing extension provided the possibility for the parental basaltic magmas to enter upper crustal levels, where they could interact with the host rocks and form hybrid andesitic melts. 相似文献
19.
大横路式钴矿床位于辽吉元古宙裂谷带中部的老岭金、多金属成矿带中 ,是国内近年来发现和查明的新类型钴矿床。该类矿床产于古元古代老岭群富硼、碳千枚岩夹石英岩 (硅质岩 )建造之中 ;矿体由含碳绢云千枚岩、含电气石绢云千枚岩、石英岩、电英岩组成 ,呈层状、鞍状产出 ,产状与围岩一致 ;矿石中钴呈独立矿物硫钴镍矿、辉钴矿、方钴矿和含钴黄铁矿等产出。通过对矿床层控特征、矿体产状与矿石组合、矿石沉积组构、容矿岩石地球化学、热水沉积岩、稀土元素及同位素组成等几方面的研究 ,证明该矿床具有明显的海底热水沉积成因特征 ,矿床受后期热液改造叠加强烈。从而提出大横路式钴矿床为海底热水沉积 -热液叠加改造型矿床 相似文献