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1.
福建沿海堆晶辉长岩的Sm-Nd年龄及意义 总被引：1，自引：1，他引：0
本文测定了福建沿海莆田戴前山堆晶角闪辉长岩的Sm-Nd同位素年龄,由堆晶角闪辉长岩、斜长石和角闪石得到的全岩-矿物Sm-Nd内部等时线年龄为95±2Ma,记录了戴前山堆晶角闪辉长岩的结晶年龄。该年龄可能反映了辉长岩是碰撞造山带中的同构造侵入岩。 相似文献
2.
博克图南部的变质堆晶角闪辉长岩锆石U-Pb年龄测定结果为2096±36Ma,表明本区的变质堆晶角闪辉长岩形成于古元古代.结合岩石化学及岩石地球化学特征研究表明,岩石可能形成于俯冲环境,是造山作用过程中弧岩浆活动的早期产物,标志着区内一个新的构造岩浆旋回的开始,不能作为古元古代末期大陆裂解的产物. 相似文献
3.
四顶黑山岩体主要由超镁铁质岩和镁铁质岩组成。超镁铁质岩由橄榄岩、角闪橄榄岩、辉橄岩、辉石岩等组成;镁铁质岩由辉长岩、角闪辉长岩、橄榄辉长岩等组成。本次对辉长岩进行了全岩Sm-Nd同位素分析,得到的等时线年龄为327±9.0Ma,初始εNd（t）=＋3.97,表明镁铁质—超镁铁质岩中辉长岩形成于早石炭世末。属于富集地幔向亏损地幔过渡类型。这一年龄的确定,为探讨北山—天山结合部晚古生代镁铁质—超镁铁质岩的成因机制和该区的区域地质演化提供了有效的年代学依据。 相似文献
4.
牛鼻子梁岩体位于柴达木地块的北缘,出露面积约8 km2,平面形态呈长条状,主要由斜长二辉橄榄岩、斜长单辉橄榄岩、角闪二辉橄榄岩、角闪橄榄岩、角闪橄榄二辉岩、黑云母化二辉岩、角闪辉石岩、橄榄辉石角闪石岩、角闪橄榄辉长岩、细粒辉长岩、似斑状辉长岩、暗色辉长岩、辉长岩、淡色辉长岩、石英闪长岩和英云闪长岩组成。文章通过岩石学、矿物学、地球化学研究,得到锆石U-Pb年龄为(361.5±1.2)Ma,Sm-Nd等时线年龄为(347±26)Ma。研究认为,牛鼻子梁基性-超基性岩体含矿岩石产于大陆边缘环境。岩体形成于泥盆纪晚期。岩浆分异充分,岩石类型丰富,岩浆演化过程中主要发生了橄榄石和斜长石的分离结晶/堆晶作用。岩体的母岩浆应属于拉斑玄武岩质岩浆。从目前发现的矿化情况来看,牛鼻子梁基性-超基性杂岩体为含矿岩体,有很好的找矿前景。 相似文献
5.
牛鼻子梁镁铁质-超镁铁质杂岩体岩石特征 总被引：1，自引：1，他引：0
牛鼻子梁岩体位于柴达木地块的北缘,出露面积约8 km2,平面形态呈长条状,主要由斜长二辉橄榄岩、斜长单辉橄榄岩、角闪二辉橄榄岩、角闪橄榄岩、角闪橄榄二辉岩、黑云母化二辉岩、角闪辉石岩、橄榄辉石角闪石岩、角闪橄榄辉长岩、细粒辉长岩、似斑状辉长岩、暗色辉长岩、辉长岩、淡色辉长岩、石英闪长岩和英云闪长岩组成。文章通过岩石学、矿物学、地球化学研究,得到锆石U-Pb年龄为（361.5±1.2） Ma,Sm-Nd等时线年龄为（347±26） Ma。研究认为,牛鼻子梁基性-超基性岩体含矿岩石产于大陆边缘环境。岩体形成于泥盆纪晚期。岩浆分异充分,岩石类型丰富,岩浆演化过程中主要发生了橄榄石和斜长石的分离结晶/堆晶作用。岩体的母岩浆应属于拉斑玄武岩质岩浆。从目前发现的矿化情况来看,牛鼻子梁基性-超基性杂岩体为含矿岩体,有很好的找矿前景。 相似文献
6.
太行山南段西安里早白垩世角闪辉长岩的成因: 锆石U-Pb年龄、Hf同位素和岩石地球化学证据 总被引：2，自引：0，他引：2
介绍了太行山南段西安里岩体角闪辉长岩的锆石U-Pb年代学、锆石Hf同位素以及岩石地球化学资料, 以便对该类岩石的成因给予制约.西安里岩体主要由一套含橄榄石角闪辉长岩-角闪闪长岩-闪长岩构成.角闪辉长岩中的锆石自形程度较高, 内部结构均匀, 呈条痕状吸收, Th/U值介于1.44~2.85之间, 表现出岩浆成因特征, 其206Pb/238U年龄介于135~127 Ma之间, 15个点的加权平均年龄为131±1 Ma, 即角闪辉长岩形成于早白垩世; 锆石的εHf(t)值介于-23.5~-19.2之间.角闪辉长岩中SiO2=50.27%~50.89%, Mg#=0.76~0.78, Na2O/K2O=2.18~2.37, 富含过渡族元素Sc (19.2~20.3)×10-6、Cr (939~1 050)×10-6、Co (54.6~58.2)×10-6、Ni (645~718)×10-6.同时角闪辉长岩相对富含大离子亲石元素(LILEs, 如Cs、Ba、Sr)和轻稀土元素(LREEs)、强烈亏损高场强元素(HFSEs, 如Nb、Ta、Zr、Hf)和重稀土元素(HREEs).结合角闪辉长岩中纯橄岩包体和橄榄石捕虏晶的矿物化学和地球化学研究, 认为西安里角闪辉长岩是拆沉的陆壳物质熔融的熔体与地幔橄榄岩反应的产物. 相似文献
7.
《地学前缘》2017,(6):80-97
似斑状角闪辉长岩类是东天山镁铁-超镁铁杂岩的一部分,以含有嵌晶角闪石为特征,其中部分岩体的似斑状角闪辉长岩赋存铁钛氧化物矿床。为探讨东天山似斑状角闪辉长岩类和铁钛氧化物矿床形成的内在成因关系,本次研究对二红洼、牛毛泉和香山西似斑状角闪辉长岩类的斜长石、单斜辉石、斜方辉石以及嵌晶角闪石进行了系统的电子探针成分分析,并对其形成物理化学条件进行了探讨。结果表明,东天山似斑状角闪辉长岩类的母岩浆氧逸度变化范围为NNO-0.37~NNO+1.15,和攀西地区最大的红格岩体的氧逸度一致,侵入于中下地壳,深度介于8.9~15.7km,结晶温度大于914℃。东天山似斑状角闪辉长岩中铁钛氧化物矿床的富集得益于母岩浆的高氧逸度,但铁钛氧化物矿床的形成和规模则受控于各个岩体的岩浆演化程度。二红洼、牛毛泉和香山西的岩浆的演化程度系统增高,演化程度最低的二红洼岩体并未形成铁钛氧化物矿床,而分异演化程度逐渐增高的牛毛泉和香山西似斑状角闪辉长岩类则分别形成了本区一个小型的和一个大型的铁钛氧化物矿床。 相似文献
8.
出露于西南天山特克斯县东南的小哈拉军山辉长岩体主要由角闪辉长岩和含磁铁矿辉长岩组成。角闪辉长岩主要由单斜辉石、角闪石和斜长石组成;含磁铁矿辉长岩主要由斜长石和磁铁矿组成。这两类岩石都含少量方解石。这些方解石均呈独立矿物出现,且与长石、单斜辉石或黑云母平衡共生。这些方解石是原生碳酸盐矿物（不是后期热液蚀变的产物）。两类岩石属于钙碱性系列,富集轻稀土元素,亏损重稀土元素,轻重稀土之间的分异比较明显,但不显示Eu异常。辉长岩相对富集大离子亲石元素而亏损高场强元素。岩石学和地球化学研究表明,小哈拉军山辉长岩是碳酸盐化地幔极低程度部分熔融的产物,斜长石堆晶过程对岩浆演化起重要作用。 相似文献
9.
石人嶂钨矿区发育的角闪辉长岩与钨矿密切共生,研究该矿区对认识粤北地区区域地质演化、深部岩浆信息以及区域基性岩与成钨作用关系研究意义重大,但到目前为止,尚未开展相关系统的研究。文章报道了角闪辉长岩的锆石和磷灰石U-Pb年代学、地球化学资料。磷灰石U-Pb年龄指示角闪辉长岩的结晶年龄为（171±14） Ma,形成于燕山早期晚阶段古太平洋板块俯冲背景下的岩石圈伸展的构造环境,其中,锆石为捕获锆石,具有3组年龄,分别记录了区域古元古代陆核增生,新元古代古华南板块的聚合和裂解,早中生代华南板块与华北板块,印支地块聚合的后造山伸展等多起构造事件。角闪辉长岩具有低Si、K、Mn,高Ca、Fe、Mg、Na、Ti的特征,富集Rb、Ta、Zr、Ti等,亏损Ba、Nb、Sr、Hf、Be、Cs、U、Th等元素,表明其源区具有E-MORB型富集地幔的属性。角闪辉长岩的形成主要受控于软流圈地幔的部分熔融。同时,由于角闪辉长岩的高氧逸度的特征及其较石人嶂钨矿成矿更早,角闪辉长岩的存在可能主要是为后期的钨矿化的叠加提供部分Ca、Fe等元素,并为富矿流体的运移提供通道。 相似文献
10.
11.
Police, politics, and the right to the city 总被引：1，自引：0，他引：1
Mustafa Dikeç 《GeoJournal》2002,58(2-3):91-98
Space and spatiality have recently been at the core of debates concerning the political possibilities of the city. The arguments advanced in this paper might be seen as an attempt to contribute to these debates through a reflection on the spatiality of (in) justice, politics, and the right to the city. The case of French urban policy, with its focus on distressed urban areas, and the `suburban problem' in France are used as examples to make arguments more concrete. 相似文献
12.
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
13.
Influences of the unsaturated,saturated, and riparian zones on the transport of nitrate near the Merced River,California, USA 总被引：1，自引：0，他引：1
Joseph L. Domagalski Steven P. Phillips E. Randall Bayless Celia Zamora Carol Kendall Richard A. WildmanJr Janet G. Hering 《Hydrogeology Journal》2008,16(4):675-690
Transport and transformation of nitrate was evaluated along a 1-km groundwater transect from an almond orchard to the Merced River, California, USA, within an irrigated agricultural setting. As indicated by measurements of pore-water nitrate and modeling using the root zone water quality model, about 63% of the applied nitrogen was transported through a 6.5-m unsaturated zone. Transport times from recharge locations to the edge of a riparian zone ranged from approximately 6 months to greater than 100 years. This allowed for partial denitrification in horizons having mildly reducing conditions, and essentially no denitrification in horizons with oxidizing conditions. Transport times across a 50–100-m-wide riparian zone of less than a year to over 6 years and more strongly reducing conditions resulted in greater rates of denitrification. Isotopic measurements and concentrations of excess N2 in water were indicative of denitrification with the highest rates below the Merced River. Discharge of water and nitrate into the river was dependent on gradients driven by irrigation or river stage. The results suggest that the assimilative capacity for nitrate of the groundwater system, and particularly the riverbed, is limiting the nitrate load to the Merced River in the study area. 相似文献
14.
扬子北缘马元铅锌矿床闪锌矿微量元素及S-Pb-He-Ar-C同位素地球化学研究 总被引：7，自引：3，他引：4
马元铅锌矿床是近年扬子陆块北缘铅锌找矿的新突破。矿体呈层状、似层状产于碑坝隆起翼部震旦系灯影组角砾状白云岩层间构造带中,围岩蚀变很弱。矿石中硫化物以闪锌矿、方铅矿为主,中粗粒晶质结构,充填于白云岩角砾间。闪锌矿富集Cd、Ge、Ag,贫In、Tl、Se,Ga/In为6~132,Ge/In多1000,成矿温度以中-低温为主。金属硫化物ε~(34)S值相对集中,为12.9‰~19.4‰,平均为17.4‰,来自于海相硫酸盐的还原。铅同位素组成稳定,~(206)Pb/~(204)Pb为17.858~17.918:~(207)Pb/~(204)Pb为15.603~15.694;~(208)Pb/~(204)Pb为37.756~38.046,具有造山带和上地壳铅的特征,震旦系可能提供了金属成矿物质。闪锌矿中流体包裹体的~3He/~4He为0.03Ra~1.05Ra,~(40)Ar/~(36)Ar为326.1~765.1,~(38)Ar/~(36)Ar为0.183~0.204,表明成矿流体主要为地壳流体和饱和大气水(大气降水或海水)的混合。闪锌矿内流体包裹体挥发分δ~(13)C_(CH_4)值为-36.01‰~-28.80‰,δ~(13)C_(C_2H_6)值为-27.72‰~-22.44‰,δ~(13)C_(CO_2)值为-23.24‰~-9.68‰,表明有机流体参与了成矿作用。石英、方解石的H-O同位素结果表明具有海水和有机水混合的特征。可见,成矿流体具有两种流体混合的特征,一为蒸发海水与围岩反应所形成的盆地卤水,二为有机流体。推测矿区可能存在一个古油气藏,由于TSR生成一高硫气藏,为区内还原性有机流体的主要来源。当富含Pb、Zn等成矿物质的成矿流体运移至富含CH_4和H_2S的还原性流体的矿区角砾岩带时,两种流体混合,Pb、Zn等遇到H_2S发生反应而沉淀成矿,并伴生热液白云石等,形成了马元铅锌矿床。综上所述,我们认为马元矿床属MVT型铅锌矿床。 相似文献
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16.
I. M. Gorokhov M. A. Semikhatov M. M. Arakelyants E. A. Fallick N. N. Mel’nikov T. L. Turchenko T. A. Ivanovskaya T. S. Zaitseva E. P. Kutyavin 《Stratigraphy and Geological Correlation》2006,14(3):260-274
Clay subfractions (SFs) of <0.1, 0.1–0.2, 0.2–0.3, 0.3–0.6, 0.6–2 and 2–5 μm separated from Middle Riphean shales of the Debengda Formation are studied using the TEM, XRD, K-Ar and Rb-Sr isotopic methods. The oxygen and hydrogen isotope compositions in the SFs are studied as well. The low-temperature illite-smectite is dominant mineral in all the SFs except for the coarsest ones. The XRD, chemical and isotopic data imply that two generations of authigenic illite-smectite different in age are mixed in the SFs. The illite crystallinity index decreases in parallel with size diminishing of clay particles. As compared to coarser SFs, illite of fine-grained subfractions is enriched in Al relative to Fe and Mg, contains more K, and reveals higher K/Rb and Rb/Sr ratios. The Rb-Sr age calculated by means of the leachochron (“inner isochron”) method declines gradually from 1254-1272 Ma in the coarsest SFs to 1038-1044 Ma in finest ones, while the K-Ar age decreases simultaneously from 1225–1240 to 1080 Ma. The established positive correlation of δ18O and δD values with dimensions of clay particles in the SFs seems to be also consistent with the mixing systematics. The isotopic systematics along with data on mineral composition and morphology lead to the conclusion that mixedlayer illite-smectite was formed in the Debengda shales during two periods 1211–1272 and 1038–1080 Ma ago. The first period is likely close to the deposition time of sediments and corresponds to events of burial catagenesis, whereas the second one is correlative with the regional uplift and changes in hydrological regime during the pre-Khaipakh break in sedimentation. 相似文献
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18.
Over the past decade researchers working on the rocks of the Beaufort Group in the main Karoo Basin of South Africa have vastly increased our understanding of this important Permo-Triassic sequence. Many new fossil forms have been discovered, allowing for breakthroughs into the biodiversity, biogeography and biostratigraphy of the group. Taxonomic and phylogenetic advances are many and varied, and cover most of the vertebrate taxa, but with emphasis placed on the temnospondyl amphibians, archosauriforms and non-mammalian synapsids, in particular the anomodontia. Biostratigraphic breakthroughs have centered on the Middle Permian Eodicynodon and Tapinocephalus assemblage zones, the Late Permian Dicynodon Assemblage Zone, and the Triassic Lystrosaurus and Cynognathus assemblage zones. Correlation of these biozones with better dated sequences in Europe, Russia and China has allowed for many chronostratigraphic refinements, which are in turn vital for sequence stratigraphical analysis of the basin fill. Based on fossil data, both the lower (Ecca–Beaufort) and upper (Beaufort–Molteno) contacts of the group have been proved to be highly diachronous. The refined chronostratigraphic framework has also allowed for a better analysis of the basin evolution through time, particularly in terms of the correlation of external stimuli that affect basin sedimentation patterns. 相似文献
19.
Delivery of Trace Metals (Al,Fe, Mn,V, Co,Ni, Cu,Cd, Ag,Pb) from the Trinity River Watershed Towards the Ocean 总被引：2，自引：0，他引：2
The Trinity River (Texas, USA) contains in its watershed 23 different reservoir lakes, the largest one being Lake Livingston
situated in the lower Trinity River watershed and two potentially polluting metroplexes, Dallas and Houston. In order to determine
fluxes of nutrients and trace metals to Galveston Bay, a survey that included 24 discreet samples collected over a year and
at various stages of discharge was carried out during 2000–2001. Geochemical (i.e., sorption by Fe oxyhydroxides), biological
(i.e., seasonal uptake by sinking algae in Lake Livingston), and hydrological (i.e., dilution effects by increasing flow rates)
controls were found to be mainly responsible for variations in dissolved trace metal concentrations rather than pollution
sources. The Trinity River loads of suspended sediments and pollutant trace metals entering Galveston Bay at Anahuac were
<20% of those reaching Lake Livingston, and only a few percent of the total upstream trace metal load is entering the Gulf
of Mexico. Thus, during the transit through the 23 man-made lakes and an estuary, >96% of the pollutant trace metal load is
lost to sediments. 相似文献