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Search Results: 1 - 10 of 5450 matches for " ultramafic complex "
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The age of the Gaojiacun mafic-ultramafic intrusive complex in the Yanbian area, Sichuan Province: Geochronological constraints by U-Pb dating of single zircon grains and40Ar/39Ar dating of hornblende
Weiguang Zhu,Hailin Deng,Bingguang Liu,Chaoyang Li,Yu Qin,Yaonan Luo,Zhide Li,Daohui Pi
Chinese Science Bulletin , 2004, DOI: 10.1007/BF03184040
Abstract: The Gaojiacun mafic-ultramafic intrusive complex in the Yanbian area, Sichuan Province, is a stratiform intrusive body that has undergone intensive magmatic differentiation. This intrusive body involves two magmatic accumulating cycles. Systematic U-Pb dating of single zircon grains and40Ar/39Ar dating of hornblende were conducted, and the results showed that the age of hornblende gabbro, which was formed at the main phase of intrusion of the Gaojiacun intrusive complex, is 840–5 Ma, casting doubt on the concept of “Yanbian Ophiolite”. It is believed that the formation of the Gaojiacun intrusive complex seems to be related to a super-mantle plume underneath the super-continent Rodinia. The above research results are helpful for us to get a better understanding of the characteristics of Neoproterozoic tectonic evolution of the Yanbian area in Sichuan Province.
Geología y geofísica del cuerpo máfico-ultramáfico Las Ca?as, Provincia de San Luis
Ortiz Súarez,Ariel; Morosini,Augusto; Ulacco,Humberto; Carungo Durán,Andrés;
Serie correlaci?3n geol?3gica , 2012,
Abstract: las ca?as is an elongated stock located to the ne of san luis province. its structure is concordant with that of the country rock and has a size of 800 m wide by 2 km long, located in schists belonging to the las aguadas metamorphic complex (conlara metamorphic complex) with n 20o - 30o schistosity and an eastward high angle dip. the predominant facies is a gabbro that shows magmatic stratification and contains ultramafic sectors of up to 50 m in diameter; in some cases the rock is a pyroxenic hornblendite formed by poikilitic amphibole crystals with inclusions of clinopyroxene, altered olivine and opaque minerals. these rocks show alteration and mineralization of ni, cr, fe, zn and platinum group elements. the geomagnetic terrestrial survey reveals an anomaly in the mineralized zone that coincides with the ultramafic rocks, with positive and negative peaks of 1955 and -480 nt that are close to each other. contrasts of approximately 500 in nt amplitude characterize the igneous body without mineralization, whereas the metamorphic host rocks rarely exceed 100 nt. the geochemical features indicate that the las ca?as body is formed by two groups of rocks, one with high values of mgo and the other predominantly tholeitic, with the former case possessing between 2 and 22 ppb of pt or pd.
Metamorphic evolution and U-Pb zircon SHRIMP geochronology of the Belizário ultramafic amphibolite, Encantadas Complex, southernmost Brazil
Hartmann, Léo A.;Santos, Jo?o O.S.;Leite, Jayme A.D.;Porcher, Carla C.;Mcnaughton, Neal J.;
Anais da Academia Brasileira de Ciências , 2003, DOI: 10.1590/S0001-37652003000300010
Abstract: the integrated investigation of metamorphism and zircon u-pb shrimp geochronology of the belizário ultramafic amphibolite from southernmost brazil leads to a better understanding of the processes involved in the generation of the encantadas complex. magmatic evidence of the magnesian basalt or pyroxenite protolith is only preserved in cores of zircon crystals, which are dated at 2257 ± 12 ma. amphibolite facies metamorphism m1 formed voluminous hornblende in the investigated rock possibly at 1989 ± 21 ma. this ultramafic rock was re-metamorphosed at 702±21 ma during a greenschist facies eventm2; the assemblage actinolite + oligoclase + microcline + epidote + titanite + monazite formed by alteration of hornblende. the metamorphic events are probably related to the encantadas orogeny (2257±12 ma) and camboriú orogeny (~ 1989 ma) of the trans-amazonian cycle, followed by an orogenic event (702±21 ma) of the brasiliano cycle. the intervening cratonic period (2000-700 ma) corresponds to the existence of the supercontinent atlantica, known regionally as the rio de la plata craton.
Metamorphic evolution and U-Pb zircon SHRIMP geochronology of the Belizário ultramafic amphibolite, Encantadas Complex, southernmost Brazil
Hartmann Léo A.,Santos Jo?o O.S.,Leite Jayme A.D.,Porcher Carla C.
Anais da Academia Brasileira de Ciências , 2003,
Abstract: The integrated investigation of metamorphism and zircon U-Pb SHRIMP geochronology of the Belizário ultramafic amphibolite from southernmost Brazil leads to a better understanding of the processes involved in the generation of the Encantadas Complex. Magmatic evidence of the magnesian basalt or pyroxenite protolith is only preserved in cores of zircon crystals, which are dated at 2257 ± 12 Ma. Amphibolite facies metamorphism M1 formed voluminous hornblende in the investigated rock possibly at 1989 ± 21 Ma. This ultramafic rock was re-metamorphosed at 702±21 Ma during a greenschist facies eventM2; the assemblage actinolite + oligoclase + microcline + epidote + titanite + monazite formed by alteration of hornblende. The metamorphic events are probably related to the Encantadas Orogeny (2257±12 Ma) and Camboriú Orogeny (~ 1989 Ma) of the Trans-Amazonian Cycle, followed by an orogenic event (702±21 Ma) of the Brasiliano Cycle. The intervening cratonic period (2000-700 Ma) corresponds to the existence of the Supercontinent Atlantica, known regionally as the Rio de la Plata Craton.
THE EAST XINJIANG-TYPE MAFIC-ULTRAMAFIC COMPLEXES IN OROGENIC ENVIRONMENTS
造山带环境中的东疆型镁铁—超镁铁杂岩

Gu Lianxing,Zhu Jianlin,Guo Jichun,Liao Jinjuan,Yan Zhenfu,Yan Hao,
顾连兴
,王金珠

岩石学报 , 1994,
Abstract: 新疆东部黄山-镜儿泉一带产有大-中型铜镍矿床的镁铁-超镁铁岩体是中石炭统弧后盆地引张环境下的热侵位产物,主要岩石类型有橄榄岩、辉橄岩、橄辉岩、二辉岩、辉长苏长岩、苏长辉长岩、辉长岩、橄长岩、辉长岩和闪长岩等;其超镁铁岩相对富铁.不具变质组构,并具橄榄石+斜方辉石+单斜辉石+角闪石±斜长石矿物组合;岩石化学以富硅、贫碱、贫铝、贫钙为特征,并具拉斑玄武岩系演化趋势。这些岩体是造山带杂岩体的一种新类型,可称为东疆型。
Petrological and mineralogical characteristics of Hongshishan mafic-ultramafic complex in Beishan area, Xinjiang: Implications for assimilation and fractional crystallization
新疆北山地区红石山镁铁-超镁铁岩体的岩石矿物学特征:对同化混染和结晶分异过程的启示

SU BenXun,QIN KeZhang,SUN He,TANG DongMei,XIAO QingHua,CAO MingJian,
苏本勋
,秦克章,孙赫,唐冬梅,肖庆华,曹明坚

岩石学报 , 2009,
Abstract: Fractional crystallization and assimilation constrain lithological composition and fraction, and play a key role in the formation of intrusive complex. Both processes can modify mineral compositions and the order of crystallization and have important significances for petrogenesis and associated metallogenesis. Hongshishan mafic-ultramafic complex in Beishan area (Xinjiang) displays gradual transition in lithology and mineral modal, which demonstrates fractional crystallization. Si, Na, Al, Ca in plagioclase and Si, Al, Ti, Ca, Mg in clinopyroxene have systematic variations and indicate assimilation in different extent. Whereas, olivine and spinel are not sensitive to assimilation process, but multiple magma injection in terms of Fo, Ni and Cr#, Ti contents. These assumptions inferred from mineral chemistry are consistent with those from whole rock compositional variations. Therefore, mineral chemistry is an alternative tool to trace magma evolution.
Petrological study for origin of Nanshanling garnet peridotite from Dabie Mountain
大别山南山岭石榴橄榄岩成因的岩石学研究

LU FengXiang,JIN ZhenMin,SANG LongKang,CHU LingLin,JIN ShuYan,
路凤香
,金振民,桑隆康,储玲林,金淑燕

岩石学报 , 2007,
Abstract: 大别山罗田穹隆东南侧的南山岭石榴橄榄岩岩体面积小(173×133m~2),由贵橄榄石(75%)。透辉石(10%)和镁铝石榴石(15%)组成。本文通过岩石学及地球化学研究,并与大别山的碧溪岭、毛屋、饶拔寨、芝麻坊岩体以及其他地区的基性岩浆杂岩体(如红格岩体、元宝山岩体、柴北缘岩体)、残留地幔块体(五大连池、鹤壁、山旺)等不同成因的超镁铁岩进行对比后认为,该岩体属于火成成因,是镁铁-超镁铁杂岩体的一部分。表现在:橄榄岩呈块状构造,矿物分布均匀未见定向排列,镜下呈现典型的火成结构;FeO~T含量高(21.36%),Mg~#(0.77)低,Mg Ni/Fe Mn(3.06)<7,V(175.5×10~(-6))含量高于地幔块体成因的橄榄岩;REE总量偏低,LREE弱富集,(La/Yb)_N=3.1,低于饶拔寨、芝麻坊等残留地幔块体成因的橄榄岩。南山岭橄榄岩在微量元素蛛网图中,具有Ba、U、Pb、Zr、Eu的正异常和Nb的负异常,石榴橄榄岩全岩以及透辉石单矿物都具有高~(87)Sr/86 Sr(0.7088,0.7086)和低ε_(Nd)(t)(-6.55~-6.01)的特征,尽管南山岭与碧溪岭岩体距离很近而且都属于火成成因,但岩石的结构构造、变质变形的印记、REE配分形式和同位素特征都有区别,表明二者的源区及演化经历不同,相比之下,南山岭岩浆源区地壳组分的作用更为明显。在ε_(Nd)(t)-(~(87)Sr/~(86)Sr)_t图解中南山岭橄榄岩的投点十分靠近大别山北麓120~130Ma侵位的祝家铺辉石岩-辉长岩岩体群的投点分布范围,暗示可能有与罗田穹窿西北侧祝家铺岩体群的岩浆活动相对应。
Geochemical constraints on petrogenesis of Hashatubei ultramafic complex,Inner Mongolia.
内蒙古哈沙图北超镁铁杂岩体成因的地球化学制约

ZHANG MingJie,WANG TingYin,GAO JunPing,LI LiMei,
张铭杰
,王廷印

岩石学报 , 2001,
Abstract: 哈沙图北超镁铁杂岩体位于华北克拉通西北缘,具小规模多岩相的特征,主要由蛇纹石化橄榄岩、橄榄二辉岩、角闪辉石岩、异剥辉石岩及石英闪长玢岩等组成的铁质超镁铁杂岩。岩体由两大系列岩石组成:第一系列岩石结晶粗大,具平坦型稀土元素分配模式,亏损Nb、Ta、Ti等高场强元素(HFSE)和Rb、Cs、Ba等大离子亲石元素(LILE),富集U和Rb,Zr,Hf及HREE等元素含量变化较大,为大陆地壳拉张环境下富集型岩石圈地幔较高程度熔融形成的岩浆经小规模分异后分期侵入原地结晶形成的,在每期岩浆结晶初期存在一定程度的堆晶作用。第二系列岩石呈致密太,磁铁矿含量较高,岩石风化表面呈黄褐色,亏损Rb、Cs、K、Ti,富集Nb、Ta、Pb、LREE,∑REE高,为初始洋壳下富集地幔较低程度熔融形成的岩浆结晶的产物。Nd同位素组成变化较小(^143Nd/^144Nd=0.5122-0.5124),两个系列岩石中分配系数相等的微量元素比值分别分布在两个区域,岩石地球化学特征表明,该岩体为一长寿命的岩浆通道中不同源区、不同构造环境中不同期岩浆的堆积物,岩浆源区为EM1型富集地幔;表明华北克拉通西北缘在古元古代以来存在长期的陆壳增生事件,经历了拉张减薄、初始洋壳演化阶段。
Zircon U-Pb age and the geochemistry of the Baishiquan mafic-ultramafic complex in the Eastern Tianshan,Xinjiang province:constraints on the closure of the Paleo-Asian Ocean.
新疆东天山白石泉铜镍矿床基性-超基性岩体锆石U-Pb同位素年龄、地球化学特征及其对古亚洲洋闭合时限的制约

MAO QiGui,
毛启贵
,肖文交,韩春明,孙敏,袁超,闫臻,李继亮,雍拥,张继恩

岩石学报 , 2006,
Abstract: 白石泉铜镍硫化物矿床位于中天山北缘,阿齐库都克-沙泉子断裂带南侧,产于同源侵入基性-超基性复式岩体中。采用锆石激光剥蚀法(LA-ICP-MS)获得矿化辉长岩中锆石U-Pb年龄为281.2±0.9Ma。辉长岩和橄榄岩的地球化学数据表明白石泉含矿杂岩体具高Mg特征。岩石富集大离子亲石元素(Rb、Ba、K、Sr)、LREE和高场强元素(U、Pb),而具有Ce负异常和亏损高场强元素(Th、Nb、Ta、Zr、Hf)的特征。这些表明白石泉含矿杂岩体具有幔源特征和岛弧岩浆特征。结合对白石泉岩体地质特征和区域地质背景的综合分析,本文推断白石泉岩体形成于岛弧环境或活动陆缘环境,即早二叠世期间在东天山地区还存在俯冲作用,因而古亚洲洋至少应在早二叠世晚期或以后才闭合。
Trace element geochemistry of Raobazhai ultramafic complex, North Dabie Mountain
大别山北部饶拔寨超镁铁岩体微量元素地球化学

ZHI XiaChen,JIN YongBin,MENG Qing,GA TianShan School of Earth,Space Science,University of Science,Technology of Chin,Hefei,China,
支霞臣
,靳永斌,孟庆,高天山

岩石学报 , 2004,
Abstract: The major and trace element compositions of 15 samples of 5 drill cores from Raobazhai ultramafic complex are reported here. The complex is composed of upper and lower parts. The ultramafic rocks are composted of predominantly harzburgite and subordinately dunite and lherzolite. It is deduced that the ultramafic complex is a part of sub-continental lithospheric mantle with different depletion of basaltic components by partial melting of fertile mantle in different degrees from the covariance among the major element compositions of the complex. Also, the complex experienced cryptical and modal mantle metasomatism that resulted in the enrichment of incompatible elements and formation of hydrated mineral phases such as amphibole and phlogopite after mantle partial melting. Comparing LREE and LILE enrichments, it is indicated that there exist two kinds of metasomatism by two different metamorphic agencies in the complex. The LREE enrichments were probably related with silicate melt from the asthenosphere by small degree partial melting, while the LILE (for example, Rb, Ba and K etc.) enrichments were probably related with the liquid from the subduction zone by devolatilization. The effect of metasomatism in lower part of the complex was stronger than that in upper part.
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