共查询到20条相似文献，搜索用时 31 毫秒
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传统型铂族矿产，系指与镁铁质岩浆成矿作用有关的铂族矿产资源。华力西运动时期，扬子地台西南缘沿超壳深断裂带发生的大陆裂谷作用，为来自上地幔的镁铁质(拉斑玄武岩质)岩浆的上涌和侵位提供了极为有利的前提条件。含铂基性超基性岩的时空分布，受到大陆裂谷作用的主要发生发展时期和裂谷活动带的控制。通过对典型矿床特征及其成矿作用的探讨，论述了扬子地台西南缘主要的铂族矿床类型；并从四维成矿的角度，阐述了对区域成矿规律的一些基本认识。 相似文献
3.
高岭石对重金属离子的吸附机理及其溶液的pH条件 总被引：14，自引：0，他引：14
高岭石对Cu^2+,Pb^2+离子的吸附实验及高岭石的溶解实验表明,高岭石对重金属离子的吸附有别于石英单一表面配位模式,离子交换和表面配位模式并存,并随溶液pH由酸性往碱性的变化发生规律性的演替：pH<6.5时主要表现为外圈层配位的离子交换吸附,且在pH<4时由于受到高岭石表层中铝的高溶出及溶液中较高离子强度的影响,高岭石对Cu^2+,Pb^2+离子的吸附率较低,pH为5～6时由于高岭石端面的荷电性为近中性,吸附率则有明显的提升并且表现为一个吸附平台;pH>6.5时离子交换和表面配位均为重要吸附机制,pH再升高时沉淀机制则起着重要作用。研究表明,pH调控高岭石-水界面溶解与质子化-去质子化反应过程,并影响着Cu^2+,Pb^2+离子的吸附行为。最后采用Sverjensky(1993)表面配位的物理模型对吸附结果作了描述。 相似文献
4.
根据不同比例尺的区域地质调查成果以及综合研究资料,吉林省中部早中生代火山事件地层可初步作如下划分:晚三叠大酱缸组沉积期自早而晚有:星星哨火山事件(229.5～227.5 Ma),官马火山事件(222±10)Ma,西土山火山事件(210±19)Ma;早侏罗世板石顶子组沉积期有:双丫子东山火山事件(195.04±5.01)Ma,官马金矿火山事件(193.6 Ma);早侏罗世太阳岭组沉积期有:未命名火山事件1(188.0±19.0)Ma,未命名火山事件2(184.0±1.1)Ma,北大湖火山事件(179.4±1.1)Ma,二道沟火山事件(174.0±34)Ma。 相似文献
5.
The absolute stereochemistry of pristane in a sample of contemporary marine Zooplankton, Messel shale (Germany) and Djatibarang (Java) crude has been determined by gas Chromatographic methods. The relative stereochemistry in Irati shale (Brazil), Green River (U.S.) crude, Halibut (Australia) crude has also been determined, and confirmed for a sample of the Green River shale. The stereoisomer distributions indicate a loss of stereospecificity of the phytol-derived 6(R),10(S) pristane with increasing geological maturation. For example, the least mature geological sample, the Eocene Messel shale, contains solely the 6(R),10(S) isomer, whereas a mature sample, Djatibarang crude, contains 50% of the 6(R),10(S) isomer and 25% of each of the 6(R),10(R) and 6(S),10(S) isomers. 相似文献
6.
冲江铜矿位于世界三大斑岩成矿域的特提斯-喜马拉雅成矿域,其大地构造位置属冈底斯-念青唐古拉构造带的冈底斯陆缘火山-岩浆弧中部。矿区含矿岩体与非含矿岩体的岩性相同,很难通过肉眼或常规分析方法把它们区分开来。热释光测试结果表明,矿区岩石的热释光曲线有单峰和双峰两种,矿化主要发生在具单峰的似斑状二长花岗岩中。岩石矿化程度越强,热释光总积分强度值越小。另外,高岭土化对岩石天然热释光有叠加作用,具高岭土化的岩石明显具有更高的热释光值,且高岭土化与矿化成负相关。因此,热释光值可作为判断矿化的一个岩石标型。石英粒度统计也表明,含矿岩体的石英粒度曲线呈韵律式变化,而不含矿的岩石粒度曲线呈渐进式变化。故岩石中的石英粒度也可作为矿化的一个矿物标型。 相似文献
7.
Review of Microstructural Evidence of Magmatic and Solid-State Flow 总被引：13，自引：0，他引：13
R.H. Vernon 《Visual Geosciences》2000,5(2):1-23
Evidence of magmatic flow includes: (a) parallel to sub-parallel alignment of elongate euhedral crystals (e.g., of feldspar or hornblende) that are not internally deformed, (b) imbrication (‘tiling’) of elongate euhedral crystals that are not internally deformed, (c) insufficient solid-state strain in regions between aligned or imbricated crystals to accommodate phenocryst rotation, (d) elongation of microgranitoid enclaves without plastic deformation of the minerals, (e) magmatic flow foliations and elongate microgranitoid enclaves deflected around xenoliths, and (f) schlieren layering (if due to flow sorting) in the absence of plastic deformation of the minerals involved. These features are consistent with rotation of crystals in a much weaker medium, namely a melt phase, at a stage when the magma has become viscous enough to preserve the alignment.Evidence of solid-state flow includes: (a) internal deformation and recrystallization of grains, (b) recrystallized “tails,” (c) elongation of recrystallized aggregates (e.g. of quartz and mica), (d) grainsize reduction, (e) fine-grained folia anastomosing around less deformed relics, (f) microcline twinning, (g) myrmekite, (h) flame perthite, (i) boudinage of strong minerals, typically with recrystallized aggregates of weaker minerals (e.g. quartz and mica) between the boudins, (j) foliation passing through, rather than around enclaves, and (k) heterogeneous strain with local mylonitic zones.Several criteria suggest “submagmatic flow,” including recrystallized feldspar, inferred transitions from magmatic imbrication to solid-state S/C arrangements, evidence of c-slip in quartz, and especially evidence of migration of residual melt into lower-pressure sites.Recent experimental studies indicate that a change from grain-supported flow to suspension flow typically occurs in deforming magmas at melt contents of between 20% to 40%, and that large amounts of strain may accumulate in magmas without being recorded by the final fabric. At lower melt percentages, perhaps as low as a few percent, depending on the minerals and their shapes, strain may be accommodated by: (a) melt-assisted grain-boundary sliding, (b) contact-melting assisted grain-boundary migration, (c) strain partitioning into melt-rich zones, (d) intracrystalline plastic deformation (c-slip in quartz indicating plastic deformation at temperatures near the granite solidus), and (f) transfer of melt to sites of low mean stress. The only indication of strain in the absence of crystal plasticity may be an alignment of crystals. Moreover, magmatic flow microstructures may be destroyed by fracturing, crystal plasticity and recrystallization before the magma reaches its solidus.Many rocks show evidence of solid-state flow superimposed on magmatic flow. Evidence of magmatic flow is commonly preserved in deformed felsic metamorphic rocks: for example the alignment of rectangular K-feldspar megacrysts and of microgranitoid enclaves. However, absence of alignment does not preclude a magmatic origin for K-feldspar megacrysts in felsic gneisses, as magmatic flow may cease before the magma becomes viscous enough to preserve an alignment. 相似文献
8.
Aaron J. Slowey 《Geochimica et cosmochimica acta》2010,74(16):4693-9187
Mercury is a global contaminant of concern due to its transformation by microorganisms to form methylmercury, a toxic species that accumulates in biological tissues. The effect of dissolved organic matter (DOM) isolated from natural waters on reactions between mercury(II) (Hg) and sulfide (S(-II)) to form HgS(s) nanoparticles across a range of Hg and S(-II) concentrations was investigated. Hg was equilibrated with DOM, after which S(-II) was added. Dissolved Hg (Hgaq) was periodically quantified using ultracentrifugation and chemical analysis following the addition of S(-II). Particle size and identity were determined using dynamic light scattering and X-ray absorption spectroscopy. S(-II) reacts with Hg to form 20 to 200 nm aggregates consisting of 1-2 nm HgS(s) subunits that are more structurally disordered than metacinnabar in the presence of 2 × 10−9 to 8 × 10−6 M Hg and 10 (mg C) L−1 DOM. Some of the HgS(s) nanoparticle aggregates are subsequently dissolved by DOM and (re)precipitated by S(-II) over periods of hours to days. At least three fractions of Hg-DOM species were observed with respect to reactivity toward S(-II): 0.3 μmol reactive Hg per mmol C (60 percent), 0.1 μmol per mmol C (20 percent) that are kinetically hindered, and another 0.1 μmol Hg per mmol C (20 percent) that are inert to reaction with S(-II). Following an initial S(-II)-driven precipitation of HgS(s), HgS(s) was dissolved by DOM or organic sulfur compounds. HgS(s) formation during this second phase was counterintuitively favored by lower S(-II) concentrations, suggesting surface association of DOM moieties that are less capable of dissolving HgS(s). DOM partially inhibits HgS(s) formation and mediates reactions between Hg and S(-II) such that HgS(s) is susceptible to dissolution. These findings indicate that Hg accessibility to microorganisms could be controlled by kinetic (intermediate) species in the presence of S(-II) and DOM, undermining the premise that equilibrium Hg species distributions should correlate to the extent or rate of Hg methylation in soils and sediments. 相似文献
9.
Zhao Pengda 《中国地质大学学报(英文版)》1995,(1)
Ｇｅｏｌｏｇｉｃａｌ Ａｎｏｍａｌｙ ｏｆ Ｃｈｉｎａ￥ＺｈａｏＰｅｎｇｄａ（ＦａｃｕｌｔｙｏｆＥａｒｔｈＲｅｓｏｕｒｃｅｓ，ＣｈｉｎａＵｎｉｖｅｒｓｉｔｙｏｆＧｅｏｓｃｉｅｎｃｅｓ，Ｗｕｈａｎ４３００７４）ＷａｎｇＪｉｎｇｇｕｉ；ＲａｏＭｉｎｇｈｕ... 相似文献
10.
Origin of the difference in the distribution behavior of tellurium and selenium in a soil-water system 总被引：4，自引：0，他引：4
Teppei Harada 《Geochimica et cosmochimica acta》2008,72(5):1281-1294
The distribution behavior of tellurium (Te) between soil and water in a synthetic soil-water system was studied coupled with the speciation of Te both in soil and water phases by using X-ray absorption fine structure (XAFS) spectroscopy and a high-performance liquid chromatography connected to an ICP-MS (HPLC-ICP-MS), respectively. The results were compared with a similar data set for Se, which was simultaneously obtained in this study. The oxidation states and host phases of Te and Se in the soil samples were given by XAFS, while the oxidation states in water were given by HPLC-ICP-MS. It was found that both Te and Se in soil are mainly associated with Fe(III) hydroxides under oxic conditions. From the EXAFS analyses, the outer-sphere complex is important for the Se(VI) sorbed on Fe(III) hydroxides in soils, while Se(IV), Te(IV), and Te(VI) form inner-sphere complexes. Under reducing condition, it was found that Te(0) and Se(0) species were formed and that Se was more readily reduced to Se(0) than Te, as is predicted from their Eh-pH diagrams. The reduction process from hexavalent to zerovalent species was different between Se and Te, that is, the direct reduction from Se(VI) to Se(0) was observed for Se, while Te was reduced stepwise from Te(VI) to Te(0) via Te(IV). In terms of the distribution between soil and water, Se distribution to water was much higher than that of Te under wide redox conditions. For Se, selenate is the predominant species in water even under reducing condition due to the much higher solubility of Se(VI) than Se(IV). Furthermore, a much smaller distribution of Te in water was primarily due to the larger affinities of Te(IV) and Te(VI) to Fe(III) hydroxides than Se(VI), which originates from the formation of the inner-sphere complexes of Te(IV) and Te(VI) to Fe(III) hydroxides. 相似文献
11.
花岗岩力学特性的温度效应试验研究 总被引：9，自引：0，他引：9
通过实时高温（常温～850 ℃）加载和高温（常温～1 200 ℃）后冷却再加载两种情况下的单轴压缩试验,对不同高温下花岗岩的力学性质进行了研究,分析了两种情况下单轴抗压强度、弹性模量、纵波波速、剪切滑移应变等随温度的变化规律,并研究了热-力耦合效应。研究结果表明：（1）在实时高温加载作用下单轴抗压强度和弹性模量随着温度升高而发生连续劣化;（2）高温作用冷却后再加载,花岗岩在常温～600 ℃区间峰值强度变化不大,800 ℃左右岩样强度突然降低;（3）纵波波速随加热温度的升高而逐渐降低;（4）剪切滑移应变在800 ℃之前相对较小,且变化不大,之后便迅速增大,表现出明显的塑性;（5）提出了热-力耦合因子的概念,并借助其提出了一维非线性热-力耦合本构模型,模型曲线和试验曲线较吻合。 相似文献
12.
Types and distribution of silver ore deposits in China 总被引：2，自引：0，他引：2
Silver is generally recovered as a by- and co-product along with Au, Pb, Zn, Cu, Sb, Bi, Hg, Sn and W from polymetallic and
gold mines in China. Chinese silver deposits can be classified into five principal types according to host rocks. These types
and their host rocks are: (1) marine volcanic-sedimentary rocks hosting (la) massive sulfide Pb-Zn-(Cu)-Ag ores and (1b) stratiform
Ag-(Au) ores; (2) continental volcanic-sedimentary rocks containing (2a) various polymetallic-silver veins and/or stockworks,
and (2b) Ag-(Au) veins in pyroclastic rocks; (3) rocks affected by metasomatic processes including (3a) complex Sn-polymetallic-Ag
ores, (3b) Pb-Zn-(Cu)-Ag skarns, (3c) associated W-Ag quartz veins and/or skarns, and (3d) Ag-(Au) zones and veins in altered
carbonate rocks; (4) metamorphic-intrusive rocks, principally Ag-(Au) veins in sheared and brecciated metamorphic rocks; and
(5) sedimentary rocks including (5a) stratiform Pb-Zn-Ag ores in carbonate rocks, (5b) Ag-V mantos in black shales, and (5c)
Cu-(Ag) layers in red sandstones. A sixth grouping includes gossans. The tectonic settings, geological features, and temporal
and spatial distribution of these different types of silver occurrences indicate that silver mineralization reflects to a
great extent the evolution of tectonic environments in China throughout geological time. Type 1 is generally developed in
association with several fold belts from the Caledonian to Yanshanian orogens, while types 2, 3 and 4 correlate with rejuvenation
of the eastern China continent during the Mesozoic period. The three subgroups of type 5 are recognized in different stages
and various sedimentry and diagenetic environments during the development of paraplatforms and fold belts. Type 6 results
from recent weathering of existing sulfide ores or protores.
Editorial handling: DR 相似文献
13.
河南大湖金钼矿床成矿物质来源的锶钕铅同位素约束 总被引：10，自引：6，他引：4
河南灵宝大湖金钼矿床位于小秦岭金矿田北缘,属典型的断控脉状矿床.前人较好研究了矿床流体包裹体和成矿年代,但对成矿物质来源研究薄弱.本文对16件矿石硫化物及5件赋矿围岩样品进行了Sr-Nd-Pb同位素分析,金属硫化物I_(Sr)=0.70470～0.71312,平均0.70854;(~(143)Nd/~(144)Nd)_i=0.51143-0.51215,平均0.51162;(~(206)Pb/~(204)Pb)_i=17.033～17.285,(~(207)Pb/~(204)Pb)_i=15.358～15.438,(~(208)Pb/~(204)Pb)_i=37.307-37.582,平均值分别是17.162,15.405,37.440.5件太华超群样品I_(Sr)=0.70947～0.73201,平均0.72294;(~(143)Nd/~(144)Nd)_i=0.51076～0.51133,平均0.51107;(~(206)Pb/~(204)Pb)_i=17.127～18.392,(~(207P)b/~(204)Pb)_i=15.416～15.604,(~(208)Pb/~(204)Pb)_i=37.498～37.814,平均值分别是17.547,15.470,37.616.Sr-Nd-Pb同位素特征表明成矿物质来源具壳幔混合特征,初始成矿流体可能来源于亏损的残余洋壳,并通过成矿过程的水岩相互作用与太华超群混合;据此认为,在218Ma年左右,秦岭地区的陆陆碰撞造山作用并没有结束,而仍在进行之中. 相似文献
14.
Metamorphism of the Crystalline Basement of Central Chile 总被引：1，自引：2，他引：1
The metamorphic basement of the Cordillera de la Costa, in CentralChile, consists mainly of slate, meta-sandstone, phyllite, andmica schist but contains small quantities of greenschist. Thegreater part of the basement is comprised in the Curepto series,and is characterized by dynamo-metamorphism whose intensityincreases westward. East of this is the smaller Nirivilo series,characterized by contact metamorphism whose intensity increaseseastward toward a granodiorite batholith. At the northern endof the metamorphic belt lies the Pichilemu series, in whichthe metamorphism is dynamo-thermal and increases in intensityto the east. The rocks in the first two areas are divisibleinto zones that trend north-north-east, essentially parallelto the margin of the batholith and to the Pacific coast; butin the Pichilemu area the zoning trends north-west. In the Cureptoseries three zones were distinguished; these are, in order fromeast to west: (1) a muscovite-chlorite(-albite) slate zone,(2) a muscovite-biotite(-albite) phyllite zone, and (3) a muscovite-chlorite-albite(±garnet) schist zone. The rocks in all three zones belongto the greenschist facies; the chlorite in the third zone isbelieved to be a product of H metasomatism. In the much narrowerNirivilo area no zones were mapped, but the following eastwardsuccession of critical assemblages was recognized: (1) muscovite-biotite-chlorite-albite;(2) muscovite-biotite-chlorite-andalusite-albite; (3) biotite-muscovite-andalusite-oligoclase;(4) biotite(± muscovite)-andalusite-sillimanite (or cordierite).The muscovite in the rocks that have undergone highgrade metamorphismis largely of metasomatic origin. Part of the sillimanite hasbeen formed at the expense of biotite and andalusite. In mostof the Nirivilo area the most strongly metamorphosed rocks areof the hornblende-hornfels facies, but small parts of that areamay contain rocks of the pyroxene-hornfels facies. The Pichilemuarea comprises the following zones and subzones: (1) a biotitezone, which includes (a) a muscovite-chlorite-biotite-albitesubzone and (b) a muscovite-biotite-albite subzone; (2) a garnet-oligoclasezone; (3) a staurolite-andalusite zone; (4) a muscovite-sillimanitezone; and (5) a sillimanite-orthoclase zone which includes (a)a sillimanite-orthoclase subzone and (b) a sillimanite-orthoclase-cordierite-almandinesubzone. Some thermal metamorphism is superimposed on the regionalmetamorphism. The facies grade from the greenschist to the granuliteor intermediate between the granulite and the amphibolite facies.The three series represent different pressure conditions: theNirivilo series corresponds to a low-pressure (contact) type,Pichilemu represents a low-pressure intermediate, dynamo-thermaltype, and Curepto is a dynamothermal, high-pressure intermediatetype series. The Curepto area was affected first, the Pichilemuarea next, and the Nirivilo area last. The metamorphism in allthree series is thought to have occurred during a single tectoniccycle within Late Paleozoic time, but it was probably interruptedby periods of erosional unloading. The width of the contactaureole is thought to have been determined by the irregularexpansion of the batholith. The analogy between the metamorphicseries of the Cordillera de la Costa and Miyashiro's circum-Pacificpaired belts is briefly discussed. 相似文献
15.
A case study of long-term field performance of check-dams in mitigation of soil erosion in Jiangjia stream,China 总被引：3，自引：0，他引：3
This paper examines the long-term field performance of the check-dams in mitigation of soil erosion in the Duozhao catchment
of Jiangjia stream, southwest China. Since their construction between 1979 and 1982, the check-dams have been functioning
effectively. The examination is made via comparisons between the environmental conditions of the Duozhao catchment with its
adjacent Menqian catchment in the stream, because no check dams were constructed in the Menqian catchment. The examination
is based on recent field investigations and aerial photograph analyses, and covers four aspects: (a) bed gradients of catchment
channels; (b) stability of bank slopes; (c) rates of land erosion; and (d) vegetations on bank slopes. The field data demonstrate
that the check-dams have had the following good functions for mitigation of soil erosion: (1) restricting the channel depth
and lateral erosions, (2) protecting the channel erosion base, (3) reducing the bed gradients of debris-flow channels, (4)
fixing the channel bed, (5) stabilizing the bank slopes, as well as (6) facilitating the growth of vegetations.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
16.
塔里木盆地轮南低隆起早古生代油气藏形成的期次与时间研究 总被引：24，自引：0，他引：24
塔里木盆地轮南低隆起早古生代地层中发现有大量运移沥青及有机包裹体。本研究应用地质地球化学相结合的方法对该区沥青及有机包体进行了研究,探讨了其与油气运移与聚集的关系。结果表明这些沥青与有机包裹体可大致划分为三期 :这三期沥青反射率分别是 :1.2 0 %~ 1.35 %;0.80 %~ 0.95 %;<0.0 5 %;与之对应的三期有机包裹体特征是 :黄绿色荧光,共生盐水溶液包裹体均一温度为 80~ 90℃;绿色荧光,均一温度 6 0~ 70℃;兰绿色荧光,均一温度 10 5~ 15 0℃。沥青与有机包裹体是油气生成与运移的直接证据。轮南低隆起早古生代地层中这三期沥青与三期有机包裹体的大量发现,说明在该区曾出现过三次较大规模油气生成与运移。结合该区埋藏史,受热史推断出这三期油气运移与聚集发生在晚志留世-早泥盆世,白垩纪-早第三纪及晚第三纪。本研究成果为该区油气藏的成因研究提供了重要依据。 相似文献
17.
M. K. Singh 《Journal of the Geological Society of India》2011,77(1):35-41
The paper concerns mainly with properties of packing of the Proterozoic Chandarpur and Khairagarh sandstones of Chhattisgarh
Basin. An attempt has been made to decipher the nature of boundary between Chandarpur Group and overlying Raipur Group on
the basis of grain packing. For the purpose of study based on eight representative thin sections of Chandarpur and Khairagarh
sandstones, measurements of grain size distribution, types of grain contacts, packing density (Pd), packing proximity (Pp)
and linear regression analysis has been carried out. The relation of packing density with packing proximity of Khairagarh
sandstone shows positive correlation coefficient (r) with linear regression equation (y) and no clear trend in packing proximity
(Pp) vs grain size (Is) is observed whereas Chandarpur sandstone shows packing density increases and packing proximity decreases
with linear regression equation (y) and correlation coefficient (r). Chandarpur grain size tends to increase with packing
density (Pd) whereas packing proximity (Pp) increases but Khairagarh sandstone packing density (Pd) decrease with increase
of grain size (Is) and packing proximity (Pp) tends to increase with decrease in grain size. Above study indicates that packing
behaviour of Chandarpur sandstones and Khairagarh sandstones are entirely different. 相似文献
18.
In experiments designed to determine the manner in which copper is partitioned among selected phases that constitute geologic media, we have applied the five-step sequential extraction procedure of Chao and Theobald to the analysis of drill core, soils, and stream sediments of the Rio Vivi and Rio Tanama porphyry copper districts of Puerto Rico. The extraction procedure affords a convenient means of determining the trace-metal content of the following fractions: (1) Mn oxides and “reactive” Fe oxides; (2) “amorphous” Fe oxides; (3) “crystalline” Fe oxides; (4) sulfides and magnetite; and (5) silicates. An additional extraction between steps (1) and (2) was performed to determine organic-related copper in stream sediments.The experimental results indicate that apportionment of copper among phases constituting geologic media is a function of geochemical environment. Distinctive partitioning patterns were derived from the analysis of drill core from each of three geochemical zones: (a) the supergene zone of oxidation; (b) the supergene zone of enrichment; and (c) the hypogene zone; and similarly, from the analysis of; (d) soils on a weakly leached capping; (e) soils on a strongly leached capping; and (f) active stream sediment.The experimental results also show that geochemical contrasts (anomaly-to-background ratios) vary widely among the five fractions of each sampling medium investigated, and that at least one fraction of each medium provides substantially stronger contrast than does the bulk medium. Fraction (1) provides optimal contrast for stream sediments of the district; fraction (2) provides optimal contrast for soils on a weakly leached capping; fraction (3) provides optimal contrast for soils on a strongly leached capping.Selective extraction procedures appear to have important applications to the orientation and interpretive stages of geochemical exploration. Further investigation and testing of a similar nature are recommended. 相似文献
19.
湖光岩玛珥湖沉积物硅藻硅同位素环境示踪 总被引：2，自引：0，他引：2
硅是硅藻生长所必需的养分,硅藻在生长过程中从水体吸收主要以硅酸(H_4SiO_4)形式存在的溶解硅.硅藻δ~(30)Si_(distom)可反映硅藻吸收硅酸比例的变化,进一步可以反映湖区气候与环境变化.为探索湖泊沉积物硅藻δ~(30)Si_(distom)在指示湖泊古环境方面的潜力,我们测定了湖光岩玛珥湖沉积物硅藻硅同位素变化.研究结果表明,沉积物δ~(30)Si_(distom)变化与生物硅和有机碳含量变化呈显著相似性,可作为一种有效的古环境代用指标.同时,与已有温度记录的对比分析表明,两者具有很好一致性.较高的如δ~(30)Si_(distom)指示了温度较高的气候条件下硅藻对硅酸的利用率较高;当δ~(30)Si_(distom)较低时,对应着在温度较低的气候条件下硅藻对硅酸的利用率较低.目前,热带陆地区域古气候重建的方法中可用的温度代用指标很少,此项研究证明了δ~(30)Si_(distom)是一种很有潜力的古环境代用指标,有望在低纬度地区古温度重建中发挥重要作用,值得进一步深入研究. 相似文献
20.
M. A. Etheridge D. M. Ransom P. F. Williams C. J. L. Wilson 《Australian Journal of Earth Sciences》2013,60(4):465-470
The pre‐Devonian sedimentary and volcanic sequence exposed along the south coast of New South Wales has previously been divided into three stratigraphic groups: (1) Upper Ordovician graptolite‐bearing slate which is conformable with (2) interlayered thinly‐bedded greywacke and pelite of undifferentiated Ordovician age and (3) Cambrian successions of interlayered chert, pelite and volcanic rock at Bate‐mans Bay and Narooma. The main bases for this subdivision are a change in rock types between (1) and (2), and the unconformity between (2) and (3) formerly proposed on the basis of changes in rock type and fold style across the boundary. New structural data are presented which refute the presence of the unconformity, and conformity of (2) and (3) with the fossiliferous slates is established. 相似文献