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1.
Anil B. VALSANGKAR 《《地质学报》英文版》2011,85(4):814-825
Grain size and clay mineral distribution up to 45 cm depth in the silty clay sediments from 26 box cores from 10°to 16°S along four longitudes(73.5°-76.5°E)were studied for understanding spatial variability in the Central Indian Basin(CIB).It was observed that the average sand content in the basin is 3.8%,which decreases systematically and longitudinally to 0.3%towards south.The average illite and chlorite major clay mineral abundance also decrease southwards along the four longitudes from 10°S,and show ... 相似文献
2.
本文对太平洋ＣＣ区（Ｃｌａｒｉｏｎ－ＣｈｐｐｅｔｏｎＺｏｎｅ）多金属结核富集区的结核丰度、品位（Ｍｎ、Ｃｕ、Ｃｏ、Ｎｉ）进行了详细的地质统计学分析、获得了较好的实验变差图。分析结果表明光滑型结核富集区的丰度变程为５０～６０ｋｍ，结核水平分布连续性好，丰度稳定而变化小，结核中Ｍｎ、Ｃｕ、Ｃｏ、Ｎｉ四种金属元素变程为８０～１００ｋｍ，各向异性和空穴效应现象不明显；粗糙型结核富集区丰度变程为４０～５０ｋｍ，结核中Ｃｏ、Ｎｉ、Ｍｎ变差图拟合较困难，它们的变程约１００ｋｍ，大多数变差图形表现出有漂移、穴穴效应和各向异性现象，结合其它实际调查资料分析，影响变差函数稳健性的主要因素是粗糙型结核贫富分布不均且变化大。克立格法和算术平均法两种方法计算得出的结核资源量误差一般为１%～２%。最大误差不超过７%，这与以往的分析结果基本一致。研究结果表明，结核丰度采样间距为２８ｋｍ×２８ｋｍ，结核资源估计误差:光滑型结核区为２９.４５%的资源估计误差下降到１４.５９%，粗糙型结核区为３６.０７%；采样间距缩小到１３ｋｍ×１３ｋｍ，光滑型结核区的资源估计误差下降到１４.５９%，而粗造型结核区资源估计误差仍有２３.０１%。 相似文献
3.
Fifty buried manganese nodules at different depth intervals were recovered in 12 sediment cores from the Central Indian Ocean Basin (CIOB). A maximum of 15 buried nodules were encountered in one sediment core (AAS-22/GC-07) and the deepest nodule was recovered at 5.50 m below seafloor in core AAS-04/GC-5A. Approximately 80% of the buried nodules are small in size (2 cm diameter) in contrast to the Atlantic Ocean and Peru Basin (Pacific Ocean) where the majority of the buried nodules are large, 8 cm and >6 cm, respectively. Buried nodule size decreases with core depth and this distribution appears to be similar to the phenomenon of “Brazil Nut Effect”. Buried nodules exhibit both smooth and rough surface textures and are ellipsoidal, elongated, rounded, sub rounded, irregular and polynucleated. Buried nodules from siliceous ooze are enriched in Mn, Cu, Ni, Zn, Mo, Ga, V and Rb whereas those from red clay are enriched in Fe, Co, Ti, U, Th, Y, Cr, Nb and Rare Earth Elements (REE). Buried nodules from siliceous ooze suggest their formation under hydrogenetic, early digenetic and diagenetic processes whereas those from red clay are of hydrogenetic origin.REE are enriched more than 1.5 times in buried nodules from red clay compared to siliceous ooze. However, the mode of incorporation of REE into buried nodules from both sedimentary environments is by a single authigenic phase consisting of Fe–Ti–P. Shale-normalized REE patterns and Ce anomalies suggest that nodules from siliceous ooze formed under more oxidizing conditions than those from red clay. Nodules buried at depths between 1.5 and 2.5 m are diagenetic (Mn/Fe ratio 10–15), formed in highly oxic environments (large positive Ce anomalies) and record aeolian dust (high Eu anomalies). Chemical composition, surface texture and morphology of buried nodules are similar to those of surface nodules from the same basin. Furthermore, buried nodule compositions do not exhibit any distinct patterns within the core depth, suggesting that buried nodules neither grow nor dissolve after their burial in the sediment column. 相似文献
4.
《International Geology Review》2012,54(1):49-57
AbstractThe Antarctic Bottom Water (AABW) current plays a crucial role in storing and transporting heat, water, and nutrients around the world. However, it is impossible to monitor AABW in the Plio-Pleistocene by direct measurement. Hence, abyssal erosion was usually chosen as an effective indicator of the presence of the AABW in the Indian and Eastern Pacific Oceans during that period. Here, we report a high-resolution magnetostratigraphy of a gravity core, the JL7KGC-01A from the south of the Mariana Trench, northwest Pacific Ocean. The main results are as follows: (1) polarity data suggest that the sequence recorded the late Gauss chron to the early Brunhes chron, including the Jaramillo, Cobb Mountain, and Olduvai normal subchrons; (2) the sedimentary processes in the study area since 2.9 Ma show three stages of sedimentation: 83 cm/Ma during 2.9–1.2 Ma, 183 cm/Ma during 1.2–0.7 Ma, and no sedimentation since ~0.7 Ma; (3) the area south of the Mariana Trench experienced a significant change in the deposition rate at 1.2 Ma, which could be correlated with the intensified desertification in inland Asia, and experienced a prominent depositional hiatus since the early middle Pleistocene, which likely resulted from the enhanced/expanded AABW. Based on these new polarity data and comparisons with previous studies around the Pacific Ocean, we therefore propose that the AABW experienced a notable change during the early–mid Pleistocene transition. 相似文献
5.
Layers from one manganese nodule dredged from the Philippine Sea(16°56'N, 129°48'E; water depth, 5700 m) and 45 bulk nodules from offshore Minami-Torishima Island, Japan(23°3'N, 153°22'E; water depth, 1200 m) were analyzed chemically and their origin is discussed based on geochemical constraints. In general, Cu, Ni, Zn and Mo tend to increase with increasing Mn content, while Co, Pb, Ba, V, Sc, Th, and the rare earth elements(REEs) show less variation with increasing Mn content. Nodule 42 H from the Philippine Sea has an average Mn/Fe ratio close to 1 and shows a positive Ce anomaly, suggesting a predominant hydrogenous origin. Profiles of 230Th230 ex and Thex/232 Th ratios in the outer ~0.3 mm of nodule 42 H indicate a steady growth rate of ~1.7 mm/Myr. Nodule E30 from offshore Minami-Torishima is characterized by lower Mn, Fe, Mn/Fe(0.53) and Mo/V(0.2) ratios but higher P and Cu/Ni(0.31) ratio relative to other nodules from that area. The Ce content of E30 is unusually low(82 ppm) when compared with other nodules from the area and it is the only nodule analyzed with a negative Ce anomaly(-0.64). Based on the geochemical data we suggest that most nodules from offshore Minami-Torishima are primarily of hydrogenous origin except E30, which is dominated by hydrothermal input, and E45, which has about a 35% hydrothermal contribution. 相似文献
6.
Tourmaline nodules from Capo Bianco aplite (Elba Island,Italy): an example of diffusion limited aggregation growth in a magmatic system 总被引：1，自引：0，他引：1
The morphology of tourmaline nodules occurring in the Capo Bianco aplite (Elba Island, Italy) is studied. Outcrop features
indicate that tourmaline nodules are the product of magmatic crystallization, as they are aligned along flow fields developed
within the magmatic hosting mass. Mesoscopic observations indicate that nodule morphologies are very variable, from rounded
to dendritic. Morphometric analyses show that tourmaline nodules are fractals and that fractal dimension quantifies their
degree of irregularity. Numerical simulations of nodule growth are performed by using a Diffusion-Limited Aggregation process.
The presence in natural samples of nodules with different morphologies is explained by considering a chaotic magmatic system
characterized by a complex interplay between growth rate in different dynamical regions, latent heat of crystallization, and
local convection dynamics. It is suggested that higher growth rates correspond to growth of tourmaline nodules in dynamical
regions where the transfer of nutrients is very efficient. In such conditions, the latent heat released by the growing nodule
is high, inducing strong local convection dynamics, destabilizing the nodule interface, and promoting the formation of dendritic
morphologies. On the contrary, the growth of nodules in dynamical regions characterized by weak transfer of nutrients is inhibited
leading to weak local convection dynamics and, consequently, to the formation of rounded morphologies. 相似文献
7.
Prosenjit Ghosh S. K. Bhattacharya A. M. Dayal J. R. Trivedi M. Ebihara M. M. Sarin A. Chakrabarti 《Journal of Earth System Science》2002,111(2):87-93
Syngenetic carbonate nodules constitute an interesting feature of the glaciogene sediments of various Talchir basins in peninsular
India. Petrographic, cathodoluminescence and sedimentary results suggest that many of these nodules contain primary carbonate
precipitates whose geochemical signatures can be used for determining environment of deposition and provenance of the sediments
and drainage source. Several nodules were collected from Gondwana basins of east-central India and analyzed for stable carbon
and oxygen isotope ratios, REE and trace element composition, and Sr isotope ratio. The mean δ18O and δ13C values of the calcites in the nodules are — 19.5% and-9.7% (w.r.t. PDB) respectively suggesting a freshwater environment
(probably lacustrine) for formation of these objects. Trace element ratios (Eu/Eu * and La/Yb) of the nodule samples show
that the source of the sediments in the Damodar valley basin was the granites, gneisses and intrusives in the Chotanagpur
region. The sediments in the Mahanadi valley were derived from granulites, charnockites and granites of the eastern ghat region.
The Sr concentration of the carbonate phase of the nodules is low, ranging from 10–60 ng/g. The87Sr/86Sr ratios of the samples from the west Bokaro basin and Ramgarh basin vary from 0.735 to 0.748 (mean: 0.739) and from 0.726
to 0.733 (mean: 0.730) respectively. These values are consistent with our proposition that water of these basins drained through
the granitic rocks of the Chotanagpur region. In contrast, the87Sr/86Sr ratios of the samples from the Talchir basin (Type area) of Mahanadi valley vary from 0.718 to 0.723 (mean: 0.719). These87Sr/86Sr ratios are close to those of the granulites in the adjoining eastern ghat belt suggesting that area as the drainage source. 相似文献
8.
湖南省民乐-古丈地区锰矿位于上扬子地块东南缘之武陵台陷的半局限浅海盆地中,为典型的海相沉积型锰矿床。区内主要有民乐和古丈2个锰矿产地,位于松桃成锰盆地的中东部,与贵州道坨锰矿、杨立掌锰矿处于同一断陷槽中,成矿地质条件较好,找矿潜力较大。通过对区内锰矿床（点）成矿地质特征、古构造、岩相古地理等综合分析,总结区域锰矿成矿规律和找矿方向,为上扬子地块东南缘南华系锰矿找矿突破提供依据。 相似文献
9.
《International Geology Review》2012,54(16):1984-1999
The South Yellow Sea basin in eastern China has experienced a multi-stage tectonic evolution history. The major structures were created when the basin was a foreland basin during the Mesozoic. However the geological evolution of the basin has not yet been corroborated by direct evidence from the underlying basement rocks. Qianliyan Island in the southern Yellow Sea provides an opportunity to study the formation and evolution of the basin by means of direct geochronological and geochemical evidence. On Qianliyan Island, basement rocks are exposed that consist of granitic gneiss, felsic gneiss and minor mylonite, and lenses of eclogite. Major and trace element characteristics of these four types of gneiss indicate that they originated from crustal material, varying in composition from pelite to greywacke. SHRIMP U-Pb zircon dating results of a felsic gneiss sample show that this rock crystallized between 659 and 796 Ma and underwent a metamorphic overprint at 229 ± 4 Ma. This age pattern resembles that of gneisses from the ultra-high-pressure terrain in the Dabie–Sulu belt. We conclude that the study area was part of the northern margin of the Yangtze Block during the Neoproterozoic. Neoproterozoic magmatic activity occurred along this margin and the basement sequence underwent Triassic metamorphic overprint during the northward subduction of the Yangtze Block beneath the North China Block. We further conclude that the deformation associated with this metamorphic event led to the formation of the southern Yellow Sea foreland basin. 相似文献
10.
Sridhar D. IYER 《《地质学报》英文版》2005,79(1):77-86
1 IntroductionMetalliferous sediments and mounds occur in all majortectonic settings in the oceans (e.g., the Galapagos Rift,East Pacific Rise (EPR), Bauer Deep and Central Basin ofthe Pacific; Heath and Dymond, 1977). Further, massivesulphide deposits and high-temperature vents have beenreported along the mid-ocean ridges (MOR). In the IndianOcean, an inactive hydrothermal field and a hydrothermalplume site have been discovered along the Central IndianRidge (CIR). The SONNE Hydro… 相似文献
11.
R. I. Nedumov 《Lithology and Mineral Resources》2006,41(1):15-26
Conditions and scales of the accumulation of dissolved manganese in waters of marine basins with hydrosulfuric contamination
are considered. It is shown that the Kalamit ferromanganese nodule field, most probably, originated due to the delivery of
manganese from the hydrosulfuric zone of the Black Sea. Precisely this source converts the normal diagenetic process of material
redistribution into the ore process. It is demonstrated that the formation of ferromanganese nodules in the Black Sea represents
an embryonic manganese ore process. Its full-scale development seems to have taken place in the Early Oligocene Maikop basin
owing to the spatiotemporal coincidence of a series of favorable conditions. 相似文献
12.
The bottom of the magnetized crust determined from the spectral analysis of magnetic anomaly is interpreted as a level of the Curie point isotherm. A spectral analysis technique was used to estimate the depth of the magnetic anomalies sources (Curie point depth analysis) of the eastern shore of the Gulf of Suez, Egypt. The depth to the tops and centers of the magnetic anomalies are calculated by azimuthally averaged power spectrum method for the whole area. The results obtained suggests from this study showed that the average depth to the top of the crustal block ranges between 1.15 and 1.9 km, whereas the average depth to the center of the deepest crustal block ranges between 9.1 and 12.7 km. Curie point depths in the study area range between 14.5 km in the northwestern part of the study area and 26 km in the southeastern part of the study area. The results imply a high geothermal gradient (34.7 °C/km) and corresponding high heat flow value (72.87 mW/m2) in the northwestern part of the study area. The southeastern part of the study area displays a low geothermal gradient (24.26 °C/km) and low heat flow value (50.9 mW/m2). These results are consistent with the existence of the possible promising geothermal reservoir in the eastern shore of the Gulf of Suez especially at Hammam Faraun area. 相似文献
13.
随着全球经济的发展,世界各国都面临着严峻的资源危机,而开发利用深海固体矿产资源已成为许多国家的重要选择。人们越来越意识到,海洋已经成为实现新世纪人类社会经济可持续发展的重要空间。随着中国大洋调查的进展,有必要系统梳理世界国际海域深海多金属结核资源调查历程、研究现状及进展。深海多金属结核资源作为可能是海底分布最广、储量最大的金属资源,历来得到国际和国内学者的广泛关注。近几十年的调查和估算表明,全球海洋中大约覆盖了54×106km2的多金属结核,有商业开采潜力的资源量达75×109t。但是很多海域涉及到具体区域性的资源调查工作还有待开展,同时在新的理论认识如热液成因和生物化学作用在多金属结核形成过程中的影响以及如何使金属提取过程更加绿色环保和科学高效等学科已经逐渐成为各国学者关注的新方向。中国应该合理有效开展具有针对性的多金属结核调查,争取使中国在深海海域矿产资源的调查和开发工作中走在国际前列。 相似文献
14.
Alan L. Mayo Rachel M. Henderson David Tingey William Webber 《Hydrogeology Journal》2010,18(3):725-747
The 1,750-km2 endorheic Honey Lake basin (California–Nevada, USA) was part of the 22,000-km2 Pleistocene Lake Lahontan pluvial lake system which existed between 5,000 and 40,000 years BP. The basin consists of two subbasins separated by a low elevation divide. Groundwater in the western subbasin has a maximum total dissolved solids (TDS) content of only ～1,300 mg/L; however eastern subbasin groundwater has a maximum TDS of ～46,000 mg/L. This TDS distribution is unexpected because 94% of surface water TDS loading is to the western subbasin. In situ reactions and upwelling thermal groundwater contributing to groundwater chemistry were modeled using NETPATH. The TDS difference between the subbasins is attributed to post-Lake Lahontan isostatic rebound about 13,000 years ago. Prior to rebound the subbasins did not exist and the low point of the basin was in the eastern area where hydraulic isolation from the larger Lake Lahontan and frequent desiccation of the basin surface water resulted in evaporite mineral deposition in accumulating sediments. After rebound, the terminal sink for most surface water shifted to the western subbasin. Although most closed basins have not been impacted by isostatic rebound, results of this investigation demonstrate how tectonic evolution can impact the distribution of soluble minerals accumulating in shallow basins. 相似文献
15.
《International Geology Review》2012,54(14):1806-1824
In this article, we present in situ U–Pb and Lu–Hf isotope data for Upper Triassic detritus in the Sichuan region of northwestern South China, which was a foreland basin during the Late Triassic. The aim is to determine the provenance of sediments in the foreland basin and to constrain the evolution of the surrounding mountain belts. U–Pb age data for the Late Triassic detrital zircons generally show populations at 2.4–2.6 Ga, 1.7–1.9 Ga, 710–860 Ma, 410–460 Ma, and 210–300 Ma. By fitting the zircon data into the tectonic, sedimentologic, and palaeographic framework, we propose that the north Yangtze Block and South Qinling–Dabie Orogen were the important source areas of sediments in the northern part of the foreland basin, whereas the Longmen Shan thrust-fold belt was the main source region for detritus in other parts of the foreland basin. The South Qinling–Dabie Orogen could also have served as a physical barrier to block most detritus shed from the southern North China Block into the foreland basin during the sedimentation of the Xujiahe Formation. Our results also reveal that part of the flysch from the eastern margin of the Songpan–Ganzi region had been displaced into the Longmen Shan thrust-fold belt before the deposition of the foreland basin sediments. In addition, the Lu-Hf data indicate that Phanerozoic igneous rocks in central China show insignificant formation of the juvenile crust. 相似文献
16.
There are many tiny ferromanganese nodules that cannot be found and eliminated easily in Quaternary red clay in southern China. The existence of these tiny ferromanganese nodules may influence grain size analysis results. Therefore, this paper focuses on the effects of the ferromanganese nodules on the grain size analysis and the effects of hydrochloric acid (HCl) on removing these nodules. The experimental results showed that the nodules clearly influenced the results of grain size analysis. The tiny ferromanganese nodules increased the coarse fraction and show a low peak in the coarse fraction of >100 μm on the frequency curves. The addition of HCl in the pretreatment process of grain size analysis can eliminate the effects of these tiny nodules effectively. Additionally, the HCl reacts with clay minerals and causes a reduction of the <4 μm fraction. 相似文献
17.
P. Halbach H.-J. Gursky M. M. Gursky R. Schmidt-Effing W. V. Maresch 《Mineralium Deposita》1992,27(2):153-160
Horizons of several types of Upper Jurassic to Lower Cretaceous manganese nodules occur locally in sequences of radiolarian cherts within the Nicoya Ophiolite Complex (NW Costa Rica). Field studies, X-ray diffraction analysis, petrographic, chemical and experimental studies give evidence of a sedimentary, early diagenetic origin of the nodules, in contrast to earlier suggestions. Smooth, discoidal, compact and very dense nodules with diameters of some mm to 9 cm dominate. They are characterized by braunite, hollandite, pyrolusite and quartz as well as 39–61% Mn, 0.9–1.6% Fe, 5–26% SiO2, 1.3–1.9% A12O3, 1.5–3.0% Ba, 460–5400 ppm Cu, 85–340 ppm Ni and 40–130 ppm Co, among others. It is suggested that the original mineralogy (todorokite?) was altered during thermometamorphic (braunite) and hydrothermal (hollandite, pyrolusite) events. Petrographic similarities between the fossil nodules and modern deep-sea nodules are striking. Using standard hydrothermal techniques in an experimental study it is shown that under special conditions, braunite can be produced from modern nodule material. 相似文献
18.
通过在中印度洋海盆结核区外的印度洋其他海域内收集到的298处多金属结核站位的分布、成分和赋存环境等地质特征,圈定了5处资源潜力区.文章对这些区域内海洋长周期沉积速率、底层水含氧量、底质类型、夏季海面平均生物生产力、底栖宏生物量密度、海底地形地貌特征和海底表层沉积物有机碳含量等数据信息进行加权评估,揭示各区域结核分布密度的高低状况,辅以结核主要有用组分含量的分类,确定了印度洋内各结核区资源潜力的划分标准.笔者认为加斯科因平原结核区为印度洋多金属结核高资源潜力区,马达加斯加海盆结核区和南澳大利亚海盆西部结核区为中等资源潜力区,克洛泽海盆结核区和南澳大利亚海盆东部结核区为低资源潜力区.未来在这些区域内,尤其是加斯科因平原结核区中有希望通过进一步调查研究,精确锁定具有更高资源潜力的次级面积结核勘探区,检验和完善资源潜力评估方法,精细量化揭示这些区域的资源潜力. 相似文献
19.
YAN Yi LIN Ge XIA Bin LI Zi''an LI Zhongcheng Key Laboratory of Marginal Sea Geology Guangzhou Institute of Geochemistry South China Sea Institute of Oceanology Guangzhou Institute of Geochemistry Chinese Academy of Sciences Wushan Guangzhou Guangdong Jidong Oil Gas Administration Tangshan Hebei 《《地质学报》英文版》2005,79(2):254-263
1 IntroductionThe Yan-Liao orogenic belt lies in the northern segmentof the North China Block (NCB) (Fig. 1). During Mesozoicto Cenozoic time, it experienced intense tectono-magmaticactivation, accompanied by the formation ofintracontinental basins and widespread magmatism and is avery important area to study continental dynamics andMeso-Cenozoic tectonic evolution in eastern China. Mostof previous work in this area has focused on the formationof basement, structural style and volcano-se… 相似文献
20.
A total of 1344 manganese nodules and 187 pelagic sediments from 9 areas in the North and the South Pacific were analyzed for U by the delayed-neutron counting technique. A strong positive correlation between U and Fe in nodules and sediments suggests a co-precipitative removal from sea water into the Fe-rich ferromanganese mineral phase δ -MnO2. Enrichment of U and Fe in nodules from the northwestern slopes of two submarine hills (U between 6 and 9 ppm) in the equatorial nodule belt is thought to be caused by directional bottom water flow creating elevated oxygenized conditions in areas opposed to the flow. Economically important nodule deposits from the nodule belt and the Peru Basin have generally low U contents, between 3 and 5 ppm. Insignificant resources of U of about 4 × 105 in the Pacific manganese nodules are estimated. 相似文献