西南暗色岩铜镍硫化物矿化岩体与峨眉山玄武岩的关系--以云南金宝山岩体为例   总被引：23，自引：0，他引：23  

陶琰罗泰义  高振敏朱丹 《地质论评》2004,50(1):9-15

内容提要本文以金宝山为典型实例,根据元素地球化学特征探讨了西南暗色岩铜镍硫化物矿化岩体与峨眉山玄武岩的关系。分析表明,金宝山超镁铁岩与低钛峨眉山玄武岩在元素地球化学特征上具有一致的岩浆成因属性,两者在成岩机制上互补,低钛峨眉山玄武岩普遍经历了橄榄石结晶分异和硫化物熔离亏损作用,金宝山成矿岩体则与低钛峨眉山玄武岩同源岩浆深部分异的堆晶相相对应,由堆晶橄榄石及熔离硫化物和部分残余熔体构成的“晶-糊”侵位形成,因此认为铜镍硫化物矿床成矿岩体与低钛峨眉山玄武岩为同源异相产物。  相似文献   

康滇地轴中段西缘二叠纪火山岩岩石地球化学特征   总被引：2，自引：0，他引：2  

陈玉禄  侯浩  杨更 《四川地质学报》1999,(1)

沿扬子地台西缘与松潘甘孜造山带东缘结合部中段两侧分布的二叠纪火山岩,分别代表攀西裂谷时期海相和陆相环境中的火山喷发产物。西部为海相高钾钙碱性—碱性拉斑玄武岩系列,东部为陆相低钾钙碱性拉斑玄武岩系列;两者的来源深度不一,前者较后者相对较深。  相似文献   

四川华蓥偏岩子晚二叠世玄武岩地球化学特征及其与峨眉山大火成岩省的成因关系     

刘冉  李亚  赵立可  王尉  李宏博  李常权  李博通 《岩石矿物学杂志》2022,41(1):1-17

四川华蓥偏岩子地区位于四川盆地中东部,新发现的晚二叠世玄武岩介于茅口组(下伏)和龙潭组(上覆)之间,可与峨眉山玄武岩进行对比.矿物学和地球化学研究表明,偏岩子玄武岩属于高钛亲碱性系列,具有OIB型的稀土元素和微量元素配分模式.偏岩子玄武岩基本未遭受地壳混染,单斜辉石的结晶温度为1405～1439℃,指示源区存在异常高温...  相似文献   

Detrital record of late-stage silicic volcanism in the Emeishan large igneous province     

《Gondwana Research》2020

Silicic volcanic rocks generally constitute a minor, but key product to track the magmatic evolution in mafic rock dominated large igneous provinces (LIPs). However, for their generally late-stage nature of the silicic volcanic rocks they have a poor preservation potential due to extensive post-eruption erosion. We track the eroded volcanic rocks from the ∼260 Ma Emeishan LIP by analyzing the provenance of the LIP-derived sedimentary rocks. Sandstones from a cored succession of the Late Permian Longtan Formation in the northern Youjiang Basin are rich in volcanic rock fragments, and associated mudstones have low Al₂O₃/TiO₂ ratios. Detrital zircon grains from the Longtan Formation display typical unimodal U–Pb age spectra with a prominent peak at ca. 260 Ma. These detrital zircons show an overall geochemical affinity akin to those crystallized from within-plate/anorogenic magmas. Such petrological and geochemical characteristics are consistent with a dominant source from the Emeishan volcanic rocks. Through the sampled succession, zircon grains of ∼260 Ma from the lower Longtan Formation generally display lower U/Yb (most < 0.5) and Th/Nb (most < 10) ratios and higher εHf(t) values (mostly in the range of +3 to +8) than those from the upper part. A similar sequential variation has also been observed in the Shaiwa Formation, which is an offshore time-equivalent unit to the Longtan Formation. These consistent temporal variations through the sedimentary successions in the Youjiang Basin are interpreted to reflect erosional unroofing of the Emeishan LIP during the Late Permian. These results, integrated with previous studies on the rhyolites and trachytes in Emeishan LIP, reveal a fractional crystallization dominated petrogenetic process with diminishing crustal assimilation for the late-stage silicic volcanism.  相似文献   

A new metallogenic model of the Panzhihua giant V–Ti–iron oxide deposit (Emeishan Large Igneous Province) based on high-Mg olivine-bearing wehrlite and new field evidence     

《International Geology Review》2012,54(15):1721-1745

The Panzhihua layered intrusion hosts a giant V–Ti–iron oxide deposit with ore reserves estimated at 1333 Mt. Laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) U–Pb zircon dating of comagmatic anorthosite yields a crystallization age of 259.77 ± 0.79 million years, coeval with the Emeishan flood basalts. Recently, we identified a small wehrlite dike in microgabbroic rocks and marbles. The wehrlite consists of high-Mg olivine phenocrysts with up to 90.44 wt.% Fo. Incompatible element-normalized patterns between bulk wehrlite and clinopyroxenes in gabbro suggest that they are cogenetic. The Panzhihua parental magma is estimated to have been picritic (～10 wt.% FeO and ～16 wt.% MgO), produced by partial fusion of garnet peridotite. Much of the melting occurred in garnet-facies mantle at an initial melting temperature of about 1530°C and pressure of ～3.4 GPa, suggesting involvement of a mantle plume. The degree of partial melting was rather modest and could have been generated by plume–lithosphere interaction or ascending plume-derived melting contaminated by lithospheric mantle. Field relationships show sharp contacts between the massive ores and gabbro, between wehrlite and fine-grained gabbro, and between disseminated ores and gabbro. Considering the entire intrusion, which is locally cut by dikes or veins of anorthosite, together with the occurrence of a breccia made up of gabbro clasts cemented by disseminated ores, we suggest that different types of magmas were generated by liquid differentiation in a deeper-level chamber. This differentiation could have resulted from double-diffusive convection cells, with melt later intruding into a higher-level chamber, rather than by crystal settling or in situ growth on the floor of the intrusion. However, rhythmic layering produced by in situ crystallization only occurs in the middle of the Panzhihua intrusion and was caused by periodic fluctuation in water pressure.  相似文献   

Geochronology–geochemistry of the Cida bimodal intrusive complex,central Emeishan large igneous province,southwest China: petrogenesis and plume–lithosphere interaction     

《International Geology Review》2012,54(1):88-114

The Cida complex is situated in the Panxi region and is predominantly composed of mafic-ultramafic and syenitic rock units; minor amounts of intermediate rocks occupy the contact zone between the two major rock types. The intermediate unit is mineralogically heterogeneous and typically exhibits a mottled structure. Laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) U–Pb zircon dating shows that the mafic-ultramafic rocks and syenitic rocks formed almost coevally (243 ± 0.77 Ma and 240.5 ± 0.76 Ma, respectively). These ages may represent the end phase of the Emeishan large igneous province (ELIP) magmatism. Most of these three rock types possess alkaline and metaluminous affinities. The mafic-ultramafic, syenitic, and intermediate units have K₂O + Na₂O contents of 1.85–5.16, 6.55–10.46, and 9.55–11.54 wt.%, and SiO₂ contents of 40.06–46.70, 61.74–68.54, and 51.57–54.13 wt.%, respectively. The mafic-ultramafic unit displays ocean-island basalt (OIB)-like primitive-mantle-normalized incompatible element patterns, coupled with low initial ⁸⁷Sr/⁸⁶Sr ratios (0.7048–0.7064), positive ?_Nd(t) (0.32–2.23), and zircon ?_Hf(t) (4.53–14.17) values, consistent with a mafic plume-head origin, whereas one exceptional sample with negative ?_Nd(t) (–0.22) can be interpreted as due to the involvement of considerable amounts of enriched subcontinental lithospheric mantle. The relatively low (La/Yb) _N ratios (3.40–7.69) reflect a spinel-facies lherzolite source. The syenitic unit is characterized by enrichment in large ion lithophile elements (e.g. Rb, K, Pb) and light rare earth elements (LREEs), relative to high field strength elements (e.g. Nb, Ta, P, Ti) and heavy rare earth elements (HREEs), respectively. These features, together with their metaluminous affinities, low SiO₂ contents, lower initial ⁸⁷Sr/⁸⁶Sr ratios (0.7043), positive ?_Nd(t) (0.18), and zircon ?_Hf(t) (2.63–10.09) values as well as modelling of REEs, can be plausibly explained by crustal partial melting of juvenile basic materials beneath the Yangtze Block. In contrast, the field, petrographic observations, and geochemical signatures (e.g. the linear correlations between FeO* and MgO, K/Ba and Rb/Ba ratios) suggest that the intermediate unit may have resulted from magma mixing between the syenitic and basaltic magmas that in turn had evolved from a parental mafic-ultramafic liquid. Thus, the formation of the Cida complex can be attributed to the plume–lithosphere interaction plus partial melting of juvenile basic lower crust in response to heating of underplated plume-derived basaltic magma.  相似文献   

A correlation between the Large Igneous Provinces and mass extinctions: constraint on the end-Guadalupian mass extinction and the Emeishan LIP in South China,eastern Tethys     

《International Geology Review》2012,54(10):1215-1233

ABSTRACT

Well-documented outcrops around the Emeishan Large Igneous Province (ELIP) in South China, eastern Tethys, encompassing the end-Guadalupian mass extinction have been investigated. Correlatable sections recording the event exhibit very similar lithological characters, positive-then-negative C isotope excursions and massive biotic demise. Detailed analyses of the fossil record and carbon isotopic variations were carried out on the Guadalupian–Wuchiapingian Boundary sections over the inner, middle, outer zones of the ELIP and its margin. Due to a pronounced decrease in marine habitat area and the environmental and ecological change over this part of the Tethys, the biota crisis records show the loss of numerous tropical invertebrate taxa, and exhibit fewer genera and smaller testing sizes and low productivity. The biota crisis was a sustainable and gradual reduction in diversity over the Capitanian. The associated carbon isotopic data reveal unusually high δ¹³C(carb) values before the late Capitanian, representing higher primary productivity (or buried rate) and more ¹³C-enriched CO₂ released by hydrothermal carbonate breakdown from the upper crust into the sediments at that time. Subsequently, an accelerated negative excursion across the boundary and the gradual excursion with low carbon isotope amplitude favours an increased influx of light ¹²C sourced by the volcanism around the eastern Tethys. The very similar time–space relation between the biota crisis and the Emeishan volcanism confirms that volcanic eruptions may have triggered the biota crisis event in South China. Intensive volcanism could result in detrimental environmental and ecological stresses, habitat loss, organic material splitting, or the emission of light carbon and thermal fluid (or aerosol), implying that the losses of the shallow-marine invertebrates either occurred geologically instantaneously or in a series of closely spaced crises coinciding with the initial phase of ELIP formation. These findings in South China may reveal the causal relation between mass extinctions and LIPs in a global context.  相似文献   

应用二维经验模分解(BEMD)法提取滇东Pt、Pd 元素地球化学异常     

菅贞贞  陈永清  赵彬彬 《地质通报》2012,31(5):799-806

应用二维经验模分解(BEMD)法从滇东Pt-Pd含量数据中提取2类Pt-Pd异常,即由二维内蕴模函数3(BIMF3)表征的区域Pt-Pd异常和由二维内蕴模函数2(BIMF2)表征的局部Pt-Pd异常。根据异常产出的地质特征,区域Pt-Pd异常可进一步划分为2个亚类：其一是位于受SN向小江断裂和NE向寻甸-宣威深大断裂控制的二叠纪峨眉山玄武岩分布区的异常,其特征是具有明显的浓集中心,异常强度大;其二是分布于研究区中南部的黑色岩系中的异常,异常强度弱。其中前者是滇东Pt-Pd找矿的有利地段。局部Pt-Pd异常可进一步划分为3个亚类：①分布于玄武岩区,受SN-NE向深大断裂与其次级断裂交会域控制的异常;②分布于不同地质时期黑色岩系中的异常;③哀牢山断裂北侧与基性、超基性侵入岩有关的异常。其中,分布于玄武岩区的Pt-Pd局部异常强度高、规模大,是进一步找寻Pt-Pd资源的远景地段。  相似文献   

云南中甸峨眉山玄武岩中超基性—基性岩包体的地幔流体微观踪迹及其熔离成矿意义   总被引：1，自引：0，他引：1  

易立文  刘显凡  邓江红  任科法  余少雄  赵甫峰  李春辉  黄玉蓬  董毅  邹金汐 《现代地质》2012,26(3):421-432

通过对中甸峨眉山玄武岩中超基性—基性岩包体的岩相学、电子探针、扫描电镜和能谱分析,发现在光学显微镜下呈黑色不透明的物质,在电子显微镜下表现为硅酸盐和尖晶石族氧化物为主的超显微隐晶—非晶质集合体。结合超微晶矿物晶体化学和元素地球化学分析认为,该物质是一种具熔浆和超临界性质及地幔流体属性的富铁(微晶)玻璃,是深部地质过程中,包含于幔源岩浆并与其同步运移但互不混熔的地幔流体作用遗留的微观踪迹物质。该地幔流体在伴随幔源岩浆的结晶成岩过程中,表现出由硅酸盐→尖晶石→磁铁矿→铬铁矿→钛铁矿的熔离作用,并相应触发主岩和包体岩石的交代蚀变和金属矿化,是推动和引发地壳中成岩成矿的重要动力源和物质源。由此进一步认识到,滇西地区上地幔发育峨眉地幔柱活动,为该区二叠纪之后的不同部位和不同矿种的内生多金属成矿提供了有利的深部地质背景条件。  相似文献   

云南金平勐拉峨眉山玄武岩型铜矿矿化规律   总被引：1，自引：0，他引：1  

杨昌毕  王明聪 《云南地质》2012,(2):177-181,158

赋矿的峨眉山玄武岩系以爆发相角砾状玄武岩为底,沉积相凝灰岩为顶,可明显划分为三大火山喷发旋回和三岩性段,每一喷发旋回分别对应Ⅰ、Ⅱ、Ⅲ铜矿化层,喷发旋回与铜矿(化)体(层)间存在明显的对应关系,工业矿体由后期含矿构造热液叠加再富集而成。  相似文献