黔北务川瓦厂坪铝土矿床元素迁移规律研究

黔北务正道地区铝土矿矿床属古风化壳沉积型,成矿母岩具多源性,但主要来源于下覆的中下志留统韩家店组。本文依据Grant提出的质量平衡方程和图解法,对瓦厂坪矿床在成矿过程中元素迁移的富集、贫化（亏损）规律进行了定量研究。结果表明,主要成矿母岩韩家店组砂、页岩一中间产物铝土质页岩、粘土岩是主要元素A12O3、TiO2显著富集...     

Nature and origins of granitic regolith in bauxite mine floors in the Darling Range,Western Australia

Chemical and physical weathering of primary minerals during the formation of laterite profiles in the Darling Range has formed distinct secondary mineral and morphological zones in the regolith. Erosion and human activity such as mining have exposed large areas of lateritic regolith, and its classification is important for land management, especially for mine rehabilitation. Preserved rock fabrics within regolith may enable the identification of parent rock type and degree of weathering, thus providing explanations for variations in important physical properties such as the strength and water retention of regolith. Feldspar, quartz, biotite and muscovite in porphyritic and fine-grained monzogranite in lateritic profiles have weathered via a series of gradational changes to form saprolite and pedolith consisting of kaolin, quartz, iron oxides, muscovite and gibbsite. Local reorganisation in the upper regolith or pedoplasmation zone has included illuviation of kaolin, which may be iron oxide-stained and which has disrupted the preserved rock fabric of saprock and saprolite. Quartz grain- or matrix-supported fabrics have developed, with greater pedoplasmation resulting in a quartz-grain-supported fabric. The recognition of these processes enables the use of gibbsite grainsize and distribution in regolith to infer original feldspar grainsize. Muscovite-rich or muscovite-deficient kaolin matrix indicates where plagioclase or alkali feldspar, respectively, was present in the parent rock. In some regolith, cementing by iron oxides has faithfully preserved rock fabric. The recognition of these various regolith types provides a basis for identifying the parent materials of lateritic regolith developed from granitic and doleritic rocks. Rock fabric is sometimes preserved in iron oxide-cemented bauxite mine floor regolith (Zh) due to the pseudomorphic gibbsite grains and iron oxide cement which forms a porous, rigid fabric. Plagioclase-rich granitoid is more likely to have weathered to dense clay-rich regolith (Zp), whereas albite and alkali feldspar have weathered to quartz-rich regolith (Zm) with the random orientation of quartz grains indicating that substantial reorganisation of rock fabric has occurred. It is possible to predict the response of regolith materials exposed in mine floors to management practices including ripping and re-vegetation, thus allowing targeted use of deep-ripping and planting density based on regolith type.     

鄂尔多斯盆地延安地区奥陶系风化壳古地貌恢复

鄂尔多斯盆地东南部延安地区奥陶系马家沟组顶部发育风化壳岩溶储层,因古地貌代表了地层沉积和成岩作用的背景,因而在储层的形成和演化过程中具有重要意义。在区域构造背景和地层展布的基础上,综合利用残余厚度法和印模法,并结合铝土岩厚度分布和古沟槽识别结果,准确恢复出延安地区奥陶系风化壳古地貌分布格局。结果显示,延安地区西南部表现为古岩溶高地,中部大部分地区表现为古岩溶斜坡,东部属岩溶斜坡与岩溶盆地之间的过渡带。古地貌格局和古沟槽的分布影响了储层的形成、发育和天然气的富集。延安地区岩溶古高地、靠近侵蚀古沟槽的斜坡位置含气性较好,可能与大气水淋滤等因素导致的储层发育程度、物性好坏、不整合面之上盖层的封盖性等因素有关。     

Analysis of ASTER data for mapping bauxite rich pockets within high altitude lateritic bauxite,Jharkhand, India

Bauxite deposits of Jharkhand in India are resulted from the lateritization process and therefore are often associated with the laterites. In the present study, ASTER (Advanced Space borne Thermal Emission and Reflection Radiometer) image is processed to delineate bauxite rich pockets within the laterites. In this regard, spectral signatures of lateritic bauxite samples are analyzed in the laboratory with reference to the spectral features of gibbsite (main mineral constituent of bauxite) and goethite (main mineral constituent of laterite) in VNIR–SWIR (visible-near infrared and short wave infrared) electromagnetic domain. The analysis of spectral signatures of lateritic bauxite samples helps in understanding the differences in the spectral features of bauxites and laterites. Based on these differences; ASTER data based relative band depth and simple ratio images are derived for spatial mapping of the bauxites developed within the lateritic province. In order to integrate the complementary information of different index image, an index based principal component (IPC) image is derived to incorporate the correlative information of these indices to delineate bauxite rich pockets. The occurrences of bauxite rich pockets derived from density sliced IPC image are further delimited by the topographic controls as it has been observed that the major bauxite occurrences of the area are controlled by slope and altitude. In addition to above, IPC image is draped over the digital elevation model (DEM) to illustrate how bauxite rich pockets are distributed with reference to the topographic variability of the terrain. Bauxite rich pockets delineated in the IPC image are also validated based on the known mine occurrences and existing geological map of the bauxite. It is also conceptually validated based on the spectral similarity of the bauxite pixels delineated in the IPC image with the ASTER convolved laboratory spectra of bauxite samples.     

广西邓广圩-太平铝土矿的控矿因素及找矿前景分析

邓广圩-太平铝土矿床赋存于第四系残坡积红土层中,有埋藏浅、规模大、分布广的特点.矿床受矿源层、地层岩性、构造、地貌、气候等因素控制.结合区域矿床对比,初步认为该矿床成因类型为堆积型三水铝土矿床.在矿床地质背景基础上,着重研究分析了矿床的控矿因素,认为该区具有较好的铝土矿成矿地质条件和找矿前景,是寻找大中型铝土矿的有利地区.     

New radiometric dates on the lowest stratigraphical section (TD1 to TD6) of Gran Dolina site (Atapuerca,Spain)

Ages based on independent methods, such as combined ESR-U series, luminescence, and magnetostratigraphic analyses have been obtained for the upper stratigraphical section of Gran Dolina site (TD6 to TD11 levels). However, the chronostratigraphical framework of this European Paleolithic key site remains incomplete because of its great antiquity and the lack of reliable methods. This paper provides new radiometric dates by electron spin resonance applied to optically bleached quartz grains for the whole stratigraphic sequence. The results agree with the previous chronostratigraphical framework for the upper part of the stratigraphical sequence. The ages for the Homo antecessor remains from TD6 layer range between 800 and 900 ka. The lowest layers attributed to endogenous sediments (TD1) could be contemporaneous with the Sima del Elefante TE9 human bearing layer dated to 1.2 Ma. The results suggest a human occupation of possibly more than 1 Ma at the Gran Dolina site. This study confirms moreover the potential of ESR dating method applied on quartz in karstic environment.     

堆积铝土矿中三水铝石成因探讨

堆积铝土矿中三水铝石成因探讨谌建国，刘云华（中国地质科学院宜昌地质矿产研究所，宜昌４４３００３）关键词堆积铝土矿，三水铝石－硬水铝石矿床，三水铝石成因，大气降水淋滤我国桂西至滇东广泛发育堆积型铝土矿，资源量很大。矿体是杂基支撑的角砾堆积物，砾石和基质...     

Geostatistical modelling of lateritic bauxite orebodies in Surinam: effect of the vertical dimension

Lateritic bauxite deposits in Surinam have until now been modelled in two dimensions. The samples collected by auger drill are composited into 1 m (3 ft) intervals and the accumulated grade per hole used as the input for statistical and geostatistical studies. The aim of the study presented in this paper is to quantify the information lost by working with accumulated grades. In other words, the third dimension is taken into account, by considering successive slices with a thickness of 1 m. The composition of the bauxite orebody is characterised by the loss on ignition (LOI), silica, titanium oxide, iron oxide and aluminium oxide contents.The average grade of silica increases significantly with depth, whereas the decrease in the average LOI is only minor. The statistical study indicates two populations for silica and LOI, at least for the fourth slice (at 3–4 m from the top of the orebody) and deeper. For iron oxide a significant decrease with depth is observed, but for each slice only one population could be distinguished. For titanium and aluminium oxide no significant variation with depth and no multi-populations are observed. All these observations are linked to the weathering process, which is the process of genesis of bauxite. The higher the samples are in the profile, the more intense the weathering has been, as indicated by the leaching of silica. These observations confirm that a horizontal zoning is present.For all five parameters studied, a spatial correlation in the horizontal plane is noted for the successive slices. The range of this correlation is on average 200–250 m, and a relative nugget of 35–80% is calculated depending on the parameter and the depth position.The study presented shows clearly that there is a variation with depth. By considering accumulated values, some of this information is lost. For example, for the accumulations of silica and iron oxide no spatial correlation is observed, whereas for the individual slices a distinct spatial correlation is present.