Heavy mineral stratigraphy of sediments from the southern outer shelf of the East China Sea since the last glaciation using fuzzy C-means cluster method

Correspondence analysis and fuzzy C-means cluster methods were used to divide the stratigraphy of heavy mineral assemblages,and the sediment sources and depositional dynamics of the environment reconstructed.The assemblages were taken from marine sediments from the late Pleistocene to the Holocene in Core Q43 situated on the outer shelf of the East China Sea.Based on the variable boundaries of the mineral assemblage at 63 and 228 cmbsf (cm below sea floor),the core might have previously been divided into th...     

Provenance of Sediments Filling a Paleo-Channel that Formed on the Western Yellow Sea Continental Shelf During the Last Glacial Period

Several buried paleo-channels are located on the continental shelf of the western Yellow Sea. Research on the paleochannels is significant for both theoretical studies and practical applications. In this paper, we analyse and discuss the mineralogy of sediments in a core (SYS-0803) recovered from a buried paleo-channel on the continental shelf of the western Yellow Sea. The aim is to determine the provenance of sediments that fill the paleo-channel. The heavy mineral assemblage of sediments in the core consists of schistose minerals, common hornblende, epidote, and ilmenite. The light mineral assemblage consists of plagioclase, quartz, lithic fragments, and K-feldspar. Analysis of the compositional maturity of the sand fraction revealed a quartz/feldspar ratio of < 1. A relatively high percentage of smectite is recorded throughout the entire paleo-channel fill, with the greatest percentage in the middle to lower parts. The detrital mineral assemblage and clay mineral content indicate that the paleo-channel sediments were sourced mainly from the Huanghe River during the last glacial period.     

Distribution and provenance of detrital minerals in southern coast of Shandong Peninsula

Detrital minerals of 137 offshore and 22 river sediment samples collected from Qingdao coastal areas have been analyzed. Four mineral assemblage provinces can be classified by Q-mode cluster analysis. Factor analysis identifies two major factors that account for the total variability in most common minerals: 1) based on the relationship of quartz, hornblende, actinolite, micas, and authigenic pyrite, 41.55% of the variability is related to sediment sources; 2) based on the relationship of epidote, garnet, sphere, and ilmenite, 23.21% can be related to strong hydrodynamic conditions that control transport and sedimentation. By comparing mineral compositions of river waters in the study area, the following four mineral provenances can be identified. The Qingdao-Laoshan nearshore area has a quartz-feldspar-epidote-hornblende-limenite-limonite-sphene assemblage, which is largely attributed to relict sediment and coastal erosion. The Jimo-Haiyang nearshore area has a quartz-feldspar-hornblende-epidote-limonite-mica-actinolite assemblage, derived largely from the Wulong River and Rushan River, and is also affected by the Huanghe River, while the Qianliyan Island area in the deeper offshore area separated by a mud belt has a similar assemblage. The Haiyang-Rushan nearshore area has a quartz-feldspar-hornblende-epidote-micas-limonite assemblage, indicating multiple sources from the Rushan River, the Wulong River, the Huanghe River, and coastal erosion. The central area, located in an eddy center, has a mica-authigenic pyrite-hornblende-quartzfeldspar assemblage, indicating multiple sources dominated by Huanghe River distal sediments.     

鲁西白彦组砾岩中重矿物组合特征及其物源指示意义

白彦砾岩主要分布在剥蚀低山、丘陵斜坡地带和山麓地带寒武—奥陶纪碳酸盐岩中的岩溶地貌的溶蚀沟、溶蚀槽及洞穴等负地形中,以燧石角砾为主,砾岩中的重矿物主要为金刚石、黄铁矿、赤铁矿、磁铁矿、褐铁矿、锆石、金红石、绿帘石、磷灰石、电气石;其中重矿物的种类和重量在区域砾岩点上分布差距较大,其中赤铁矿、磁铁矿、褐铁矿分布范围最大,含量最多。重矿物组合ZTR指数分析一般在0.2～0.8之间,最低为0.00,局部达到1.0～2.0;最高值在费县南西为15.95。金刚石含量最高可达64.61mg/m~3,低者只有0.164mg/m~3,北部金刚石矿物的含量自中段向两端逐渐降低;南带则呈自中心向四周环形扩散。从重矿物相对含量和重矿物组合ZTR指数来判断金刚石矿物的物源供应来源应在泗水县和白彦镇一带。     

Heavy Minerals in Shelf Sediments off Fujian-Zhejiang Coast of the East China Sea: Their Provenance and Geological Application

To examine the composition and source variations of heavy minerals in the Fujian-Zhejiang mud belt(FZMB) over the past few hundred years, heavy minerals in 150 surficial sediment samples and two sediments cores collected from the southern FZMB were identified and analyzed. The results show that the mineral assemblage of hornblende-magnetite-epidote-chlorite is dominant in the study area. Based on the heavy mineral contents, the study area is divided into two mineral zones, namely a near-shore muddy sediment zone(zone Ⅰ) and an offshore mixed sediment zone(zone Ⅱ). The sediments from zone Ⅰ contains relatively abundant metallic minerals with proximal sediments from the Oujiang River and the Minjiang River as the primary component. The sediment from zone Ⅱ has relatively low content for minerals from the near-shore materials and is significantly affected by the Oujiang River sediments, and by the flaky minerals from the Yangtze River to a certain extent. The characteristics of heavy minerals in the cores may be affected by a variety of factors. Before the 20th century, under the influence of strong East Asian winter monsoon(EAWM), the sandy sediment in FZMB is significantly affected by the Oujiang River and the Yangtze River sediments, and relatively unaffected by near-shore terrigenous matter. In the 20th century, as the intensity of the Zhejiang-Fujian Coastal Current(ZFCC) decreased, the influence of the Minjiang coastal sand enhanced. Since the 1980s, as the collective effect of relatively weak EAWM and frequent storm surges and typhoons, the impact of the Minjiang River sediments on the FZMB sediments has increased considerably.     

Characteristics of Heavy Minerals and Quantitative Provenance Identification of Sediments from the Muddy Area Outside the Oujiang Estuary Since 5.8 kyr

The heavy mineral compositions of the sediments in core D04 with a length of 20.2 m from the muddy area outside the Oujiang Estuary along the coast of Zhejiang-Fujian Provinces have been analyzed. Core D04 can be divided into three units: DU1(0–7.4 m), DU2(7.4–11.4 m) and DU3(11.4–20.2 m). The results showed that the heavy minerals are authigenic pyrite(65.6%)– hornblende(16.0%) – epidote(4.6%) assemblages. The core sediments are mainly composed of clayey silt, which belongs to the clinoform deposit formed since 5.8 kyr, indicating a weak hydrodynamic environment. The deposition rates changed in the trend of high-low-high upward. Quantitative analysis shows that the core sediments were mainly from the suspended sediments of the Changjiang(Yangtze) River, accounting for 79.2%, with only 10.0% from Oujiang, and 10.8% from other provenance. The Oujiang-derived sediments were gradually increased from the bottom unit DU3(3.1%) to the top unit DU1(17.8%), but the Changjiang-derived sediments were gradually decreased. The source changes are closely related to the development of Yangtze River Delta and Wenzhou Bay, climate changes and human activities. During the period of 2.1–3.7 kyr, the sediment supply was greatly reduced due to the poor reclamation capacity of the river basins, resulting in a low deposition rate. Since 2 kyr, the enhancement of human activities in the Yangtze River Basin and the Oujiang River Basin led to more soils to be eroded and transported to the study area. Due to the short distance of the site of core D04 from the Oujiang River mouth, the study area received more Oujiang-derived sediments when upper unit(DU1) deposited than the lower units(DU2 and DU3).     

Features of clay minerals in the YSDP102 core on the continental shelf of the southeast Yellow Sea

Ninety-eight clay mineral samples from the YSDP102 core were analyzed by x-ray diffractometer to study the four clay minerals: illite, chlorite, kaolinite and smectite. Twenty-eight samples had been analyzed on the laser particle-siz eanalyzer to reveal the particle features of the sediments. Distribution of the clay minerals and the particle characteristics in the YSDP102 core show that the core experienced three different depositional periods and formed three different sedimentary intervals due to different sediment sources and different depositional environments. Features of the clay minerals and the heavy minerals in the YSDP102 core indicate that coarse-grained sediments and fine-grained sediments result from different sources. The Yellow Sea Warm Current has greatly influenced the sedimentary framework of this region since the current‘s formation.     

山东省东平—汶上铁矿带西侧低缓磁异常区铁矿初步验证及意义——以李官屯隐伏低缓磁异常铁矿为例

研究区位于鲁西地区重要的东平—汶上铁矿带西侧,为低缓磁异常区。通过高磁测量、井中三分量磁测、钻探验证等手段,在梁山李官屯附近低缓磁异常区发现铁矿一处,矿床类型为条带状铁建造(BIF)型铁矿。该区下伏地层主要为新太古代泰山岩群山草峪组,岩性为黑云变粒岩,局部夹磁铁石英岩、磁铁角闪石英岩,矿石的主要组成矿物为磁铁矿、黄铁矿、黄铜矿。研究区山草峪组大面积分布,根据成矿时代、赋矿层位、含铁建造及岩石组合,结合成矿规律研究分析,梁山地区的大面积条带状分布的低缓磁异常区是寻找隐伏铁矿体的有利部位。     

The Mineral Composition and Sources of the Fine-Grained Sediments from the 49.6°E Hydrothermal Field at the SWIR

We used the X-ray diffraction method to determine systematically the mineral phases in bulk sediment samples and acid undissolved residuals of the fine-grained fraction of the surface sediments from the 49.6°E hydrothermal field at the Southwest Indian Ridge(SWIR)and discussed the mineral sources of the surface sediments.The results showed that the surface sediments in this region were composed of calcareous ooze,and calcite was the dominant mineral.The sediments also contained quartz,feldspar,clay minerals,pyroxene,sphalerite,barite,serpentine,and magnetite.The quartz,feldspar,and clay minerals were exogenous minerals that mainly originated from the Namib and Kalahari deserts in southern Africa.The pyroxene,serpentine,magnetite,sphalerite,calcite,and barite were endogenous minerals from weathering of seafloor basement rocks and seafloor hydrothermal activities.The sulfide particles in the sediments were mainly deposited from upwelling plumes.     

Stratigraphic Division Based on Minor Elements in the Sediment Core Q43 from the Outer Shelf of the East China Sea： Approached Through Correspondence Analysis and Fuzzy Cluster Analysis

The multivariate statistical techniques, principal component analysis, Q-mode factor analysis, correspondence analysis and fuzzy C-means clustering were applied to analyzing the datasets of minor element concentrations in sediment samples of a core collected from the outer shelf of the East China Sea. According to the analysis results, the sediment core Q43 can be divided into three strata with different features in minor elements. The first stratum (unit Ⅰ) is characterized by higher concentrations of V, Cr, Cd and Sc, which are active and inactive elements. The second stratum (unit Ⅱ) is controlled by ultrastable elements V, Ti, Cr, Th, Sc, Pb, etc. The third stratum (unit Ⅲ) is dominated by Ni, Co, Ba, Rb and Mn, which are authigenic and volcanogenic elements. The geochemical features of the core Q43 show environmental changes in the depositional process from the Late Pleistocene to Holocene.     

冈比亚河沿岸重矿物特征及其地质意义

冈比亚河沿岸重矿物以钛铁矿、金红石、锆石为其特征，并伴有自然金、铅族、铜族等矿物。它们主要来源于古老的变质岩区。冈比亚境内有望找到钛铁矿、金红石、锆石砂矿。酉部地区的滨海钛铁矿砂矿带，具有一定的工业价值。砂金异常主要分布在冈比亚东部地区，其重矿物来源于第四纪早期的一套冲─洪积砾砂层。     

ASTER数据的斑岩铜矿典型蚀变矿物组合信息提取方法 ——以秘鲁南部阿雷基帕省斑岩铜矿区为例

 本文利用美国地质勘查局(USGS)波谱数据库,重建了斑岩铜矿典型蚀变带主要蚀变矿物在ASTER卫星数据对应的反射率曲线,综合分析了主要蚀变矿物的波谱曲线特征,建立了ASTER数据B1、B4、B6、B7和B1、B3、B4、B8主成分分析模型,分别提取典型蚀变带中泥化-绢英岩化类和青磐岩化蚀变矿物组合信息,并以秘鲁南部阿雷基帕省斑岩铜矿区为例,利用研发的技术方法,分别提取了研究区白(绢)云母、高岭石、蒙脱石、明矾石和伊利石等泥化-绢英岩化类蚀变矿物组合信息,绿泥石、绿帘石和方解石等青磐岩化蚀变矿物组合信息。同时结合区域化探资料开展了斑岩铜矿靶区遥感综合找矿预测,经高分辨卫星图像验证,与已知斑岩铜矿床对比表明,本文的方法具有较好的效果。     

GRV 051523： A new eucrite

Grove Mountains (GRV) 051523 is a newly identified eucrite, consisting mainly of coarse-grained pyroxene (62.9 vol%) and plagioclase (34.2 vol%), with less abundant opaque minerals (2.7 vol%), minor silica and tiny FeO-rich olivine (Fa75). Coarse-grained pyroxenes show exsolution of augite lamellae in pigeonite or vice versa. Width of most exsolution lamellae in pyroxenes is 1-3 μm. Opaque minerals are mainly chromite, ilmenite and sulfides. The meteorite was heavily shocked, as indicated by breccias and melt veins. Coarse-grained pyroxenes commonly contain abundant tiny or needle-like chromite inclusions with orientation, probably due to heavy shock events. Pyroxenes in various petrographic occurrences exhibit highly homogeneous compositions, indicating that GRV 051523 experienced intense thermal metamorphism in the parent asteroid 4 Vesta. GRV 051523 is classified as Type 5-6. This new eucrite will have additional constraints on chemical composition, magmatic differentiation, multi-stage shock and thermal history of Vesta.     

邹城市古路口地区金刚石原生矿找矿前景探讨

古路口位于邹城市和滕州市的交界处,属于克拉通内部活动带,是金刚石成矿有利部位。区内发现金刚石储集层出土点4处,超基性苦橄岩管1处;已经查明的苦橄岩管,经激电测深及联合剖面测量,初步断定该岩管倾向SE,倾角较大,近乎直立。自然重砂样品中主要重砂矿物为赤褐铁矿、磁铁矿、锆石、绿帘石、金属球粒、金红石等,石榴子石含量少,2个样品石榴子石在20粒以上,其余含有石榴子石的样品均在10颗以下。经人工重砂样品鉴定,主要重矿物为铬透辉石、闪锌矿、方铅矿、黄铁矿、磁铁矿、铬铁矿等,对其中透辉石及铬铁矿各50颗进行电子探针分析,初步确定了属于S5组、S11组,具备对金刚石找矿的指示作用。该次激电中梯测量,圈定极化率异常2处,异常形态呈NW向近椭圆型,异常峰值达2.0以上,在视电阻率等值线平面图上,对应相对低阻区,推断为含金属矿化引起,局部视极化率升高视电阻率降低。各种找矿信息表明,该区具备金刚石原生矿成矿环境,易于开展金刚石原生矿的勘查研究工作。     

山东沂水县常庄钛铁矿地质特征及成因探讨

沂水县常庄钛铁矿床产于中细粒含钛磁铁矿辉石角闪石岩中,该岩体既是成矿母岩又是赋矿围岩。矿体长1 800 m,平均宽75 m,控制斜深344 m,平均品位TiO28.85%,品位变化系数为104%,TFe+TiO2平均品位28.24%,品位变化系数为102%。属品位变化较不均匀的矿体。该矿床具有矿体规模大,形态简单,易于开采之特点。通过对矿床地质特征的研究,认为该矿床属基性岩浆分异型钛铁矿床,其成矿时代为古元古代。     

Assemblage characteristics of clay minerals and its implications to evolution of eolian dust input to the Parece Vela Basin since 1.95 Ma

To understand the provenance and evolution of eolian input in the last 1.95 Ma in the Parece Vela Basin in the eastern Philippine Sea, the clay mineral assemblage of a gravity core PV090510 from the basin was investigated using paleogeomagnetic dating and X-ray diffraction. The assemblage of the core mainly consisted of smectite （-46%） and illite （-40%）, with some chlorite （-10%） and kaolinite （-4%）. Analysis of the provenance of these minerals suggested that smectite was mainly derived from volcanic rocks of the Mariana Arc, while illite, chlorite, and kaolinite were mainly transported as eolian dust by the East Asian monsoon from central Asia. We used the ratio of （illite＋chlorite＋kaolinite）/smectite as a proxy for Asian eolian input to the Parece Vela Basin since 1.95 Ma. This ratio followed glacial and interglacial cycles and was consistent with the intensity of the East Asian monsoon and aridity of central Asia since 1.95 Ma. The changes of the ratio reflected three different stages of the East Asian monsoon and provenance climate.     

Sediment Characteristics,Sources, and Transport Patterns in Kompong Som Bay,Cambodia: Indications from Grain Size and Heavy Minerals

In this paper, we analyzed the grain size and heavy mineral compositions of 52 surface sediment samples collected from the Kompong Som Bay of Cambodia and the adjacent rivers to depict the marine sedimentary environments and transport processes. Heavy minerals in sediments are dominated by authigenic pyrite, siderite, and tourmaline, with average percentages of 36.52%, 29.02%, and 10.94%, respectively. Two provinces can be divided according to the spatial similarity of minerals. The sediments from Province I, covered by silt grains in the northern bay, are characterized by autogenic pyrite, indicating a weakly reducing environment;whereas in Province II, covered by sand grains in the southern bay, the siderite-tourmaline-authigenic pyrite-zircon-hornblende assemblage occurs, indicating a mild reducing environment and locally oxidizing environment. Most of the sediments in the Kompong Som Bay are introduced from the Preak Piphot River and Srae Ambel River, except that some of them in the south areas come from coastal erosion. Generally, the sediments are difficult to be transported because of the low sediment loads entering the sea and weak hydrodynamic conditions. However, they are transported from the north to the south during the tide ebbing when the hydrodynamic force is much stronger. The sediment distribution and transport patterns are controlled by many factors, including submarine topography, hydrodynamic conditions, the southwest monsoon, land contours, and sediment supply.     

鲁西太古代徂徠山杂岩体花岗质岩石成因探讨

鲁西太古代徂徕山杂岩体主要由片麻状花岗岩和钾长花岗岩构成,此外尚发育少量小规模的中粗粒、细粒闪长岩。本文着重讨论花岗质岩石的成因。徂徕山杂岩体岩石地球化学研究表明,片麻状花岗岩为深源(下地壳)花岗质岩浆侵位结晶的产物;钾长花岗岩是片麻状花岗岩在区域变质作用过程中部分熔融形成的,两者具有密切的成因联系。     

青藏高原东北缘尖扎盆地沉积物矿物特征及其古环境意义

应用X射线衍射对青藏髙原东北缘尖扎盆地加让剖面11.8~5.8 Ma的地层沉积物进行矿物分析,结果表明加让剖面沉积物矿物组分主要包括碎屑矿物、碳酸盐矿物和黏土矿物。其中,以碎屑矿物居多,主要是石英、斜长石、云母类矿物(白云母、黑云母),及少量尖晶石、辉石类矿物(普通辉石、锰钙辉石及顽火辉石等)、金红石、刚玉、磁铁矿、钛磁铁矿、榍石、霞石,偶见锆石、石榴子石、锐钛矿;碳酸盐矿物以方解石居为主,白云石占比较少;黏土矿物中,绿泥石占比最高,还有少量赤铁矿、蛭石和沸石。以全岩矿物指标研究为主,结合加让剖面沉积相演化特点,并以磁化率变化为参考,进行系统的矿物学研究,获得了尖扎盆地在11.8~5.8 Ma蕴含的古气候环境演化大致可分为4个阶段:11.8~10.0 Ma,气候干冷期;10.0~8.6 Ma,气候暖湿波动期;8.6~6.2 Ma,气候温暖湿润期;6.2~5.8 Ma,气候干冷期。在约10.0、8.6、7.2 Ma附近,主要矿物占比及组合特征有明显改变,当时的古环境状况发生急剧变化,可能揭示青藏高原东北缘在10~8 Ma期间广泛发生了一系列较强烈的构造运动,来源于周边山脉的剥蚀使得研究区沉积的近源物质增多,约7.2 Ma之后的古环境演化过程主要受青藏高原构造隆升以及全球气候变冷协同影响。     

Diagenetic control of magnetic susceptibility variation in Core MD98-2172 from the Eastern Timor Sea

Detailed mineral magnetic measurements, integrated with grain-size distribution and X-ray diffraction (XRD) analyses, were made on the marine sediments of Core MD98-2172, retrieved from the Eastern Timor Sea. Values of magnetic susceptibility in this core drop sharply down-core from ∼3.85 m deep below sediment/water interface and are very low at ∼5.35 m. However, both XRD and grain-size distribution results show no sudden change in terrigenous input during sedimentation. Mineral magnetic results indicate that the depth of ∼3.85 m may be an oxic/anoxic boundary. Therefore, the sediments below ∼3.85 m have been subjected to intense reductive diagenesis, whereas the sediments above ∼3.85 m are seldom affected. The magnetic properties of the sediments shallower than 3.85 m are dominated by pseudo-single domain (PSD) magnetite, with little down-core variation in its content and grain size. Below ∼3.85 m, the magnetic mineral assemblages that have survived in the sediments may record different stages of the reductive diagenesis: (1) the sediments from the 3.85–5.35 m interval are at the stage of iron oxide reduction; PSD magnetite is the major magnetic contributor, but it becomes less abundant and coarser down-core; (2) the sediments below ∼5.35 m are at the stage of sulphate reduction; ferrimagnetic minerals almost vanish and paramagnetic minerals contribute to down-core susceptibility variations, including pyrite as evidenced by high-temperature magnetic susceptibility measurements. However, the susceptibility variations below ∼5.35 m of Core MD98-2172 show obvious periodicity, despite the intense effect of reductive diagenesis. Furthermore, the down-core susceptibility variations are coincident with fluctuations in the quantity of fine detrital particles (<8 μm), which may come mainly from the advection of the Indonesia Throughflow (ITF) and/or river input from Timor. Therefore, for Core MD98-2172, susceptibility variation below ∼5.35 m, which potentially correspond to fluctuations in the quantity of fine particles, may record the histories of the development of the ITF and precipitation on Timor.