试论陆核边缘凹沟与火山沉积铁矿的原始面貌

迁安古陆核位于华北地台山海关台凸的中部,是迁安隆起的核心部份,在大致呈卵形的迁安古陆核两侧边缘,分布着弧形褶皱带。一、迁安古陆核及边缘褶皱带迁安古陆核的面积火约为平方公里,而其边缘弧形褶皱带的面积大约为400—500平方公里。     

白云鄂博花岗岩稀土配分型式的初步研究

白云鄂博花岗岩的稀土配分型式 该花岗岩出露于白云鄂博矿的东部和东南部。侵入于白云鄂博群中,引起围岩不同程度和不同性质的蚀变。在地质构造位置上处于内蒙台背斜向内蒙褶皱带过渡的的中间地带,多沿东西方向分布,受断裂控制。     

四川饮用天然矿泉水的基本特征

四川矿泉水在川西地区主要分布在盆周山区，且多集中在前龙门山，在川东地区则主要分布于川东褶皱束。矿泉水受构造断裂、活动断裂构造蚀变带及褶皱控制明显，或沿深大断裂深部循环，或沿褶皱层间裂隙、构造裂隙向倾伏方向富集、运移、承压出露。矿泉水类型较为单一，以锶、偏硅酸及其复合型为主，多为淡矿泉水，应注意寻找锌、硒、碘等稀有类型的矿泉水。     

浅析碎裂蚀变花岗岩型铀矿床的特点和形成条件

碎裂蚀变花岗岩型铀矿床是当前我国找矿的主攻方向之一，它具有大碎裂带、以交代作用为特征的大蚀变带。低品位大矿量易浸出的特点。该类型矿床形成的主要地质条件是：地台边缘活动带或褶皱带的花岗岩隆起区；受非造山的大复式花岗岩基内自变质作用发育的小岩体和双断裂夹持区或断裂构造结的双重控制；酸交代或碱交代蚀变发育区；红层不整合覆盖、负地形、表生叠加富集区。同时，强调了在找矿过程中要加强地浸试验和经济技术评价。     

陕西省山阳县王家坪金矿成因探讨

<正>王家坪金矿大地构造位于秦岭褶皱系南秦岭印支褶皱带凤县-镇安褶皱束,山阳-凤镇断裂和镇安-板岩镇断裂之间。区域岩浆活动剧烈,山阳-凤镇断裂两侧有晚元古代-加里东期花岗岩、印支期酸性岩和印支期岩浆活动伴生产物的纳长角砾岩出露。本文在综合利用前人资料基础上,对王家坪金矿地     

花岗岩成因和大地构造演化

基于中国地质资料和构造演化序列,作者将花岗岩石划分成三大类型和十三个亚类,它们分别是: 地槽阶段的花岗质岩石:早期(1)大洋岛弧M型花岗质岩石;晚期(2)褶皱带轴部S型花岗质岩石(褶皱变质重熔型);(3)沿造山带两侧发育的韧性剪切带S型花岗岩(断裂-变质型);(4)大陆边缘或岛弧Ⅰ型花岗质岩石;(5)造山期后沿着断裂带分布的高层位侵入型花岗岩(断裂-重熔型)和A型花岗岩。活化阶段(地洼阶段)的花岗质岩石:(1)地拱中的S型花岗质岩石;(2)地拱边缘混熔型花岗质岩石;(3)地拱内Ⅰ型花岗质岩石;(4)活化晚期阶段裂谷A型花岗质岩石。回返活化型花岗质岩石:(1)沿着韧性剪切带发育的S型花岗质岩(断裂-变质型);(2)混熔型花岗岩岩石;(3)A型花岗质岩石。     

一种解析正圆锥状褶皱和复杂环带的方法——三点法

圆锥状褶皱是与圆柱状褶皱几何特征不同但又有一定联系的构造,在自然界并不少见,不仅可以出现于圆柱状褶皱的尾端,而且常见于多期构造变形迭加的地区。作者在辽宁省鞍本地区进行变质岩构造解析时,也遇到了多个不同尺度的圆锥状褶皱。     

重庆市地下热水开发利用条件的初步研究

一.地下热水的地质环境本区位于新华夏系构造带四川沉降带中,分属川中褶带和川东褶带的接壤地区,川东 褶带为一系列北北东向展布的狭长的不对称的高幅度紧密褶皱,以华蓥山、铜锣峡及明月峡等背斜为主体的川东平行排列的隔挡式褶皱束,背斜紧凑,常发育有纵向断裂,据四川石油管理局地震勘探所获资料表明各高隆起背斜深部的断裂都很发育(图一)。向斜宽缓,断裂不发育。华蓥山以南构造分支,即由沥鼻峡、温塘峡及观音峡等背斜展布成帚状形式,轴线逐渐偏转呈南北向;西部合川、铜梁等地为红层分布区,褶皱平缓,背斜宽缓低平,断裂不发育。     

侧向挤压下粘土破裂实验及其地质含义

长期以来,许多学者(Chang,1984,1950;张文佑、钟嘉猷,1965;Tschlenko,1967)用粘土、松散材料或岩石做变形试验,研究破裂的形成和发展的特点,并与野外观察到的节理或破裂进行对比,取得了很大进展。诸如材料变形初期出现的吕德氏线、破裂的共轭性与褶皱构造的空间展布规律性、破裂形成过程从剪切开始到张性破裂完成(张文佑等,1983,1975),以及根据破裂的产出探讨区域构造应力场,从全球性断裂组系追溯岩石圈动力学和地壳运动力源等等。     

塔里木盆地北部构造转移形式及其成因

塔里木盆地北部褶皱－逆冲断层变形在平行于区域构造方向上通过构造转换而变化。构造转换形式包括纵向和横向两种。变形缩短程度沿走向保持均一或渐变时发生纵向转换，其中包括雁列式断裂间的转换和逆冲断层向其他构造的转换，横向转换变形缩短程度沿走向的突然变化。     

REE determination and REE distribution patterns in Meso-Cenozoic volcanic rocks of central-western liaoning province and their geotectonic implications

The REE distribution patterns in the Meso-Cenozoic volcanic rocks of central-western Liaoning Province are characterized by high LREE/HREE ratios. The REE distribution patterns in volcanic rocks ranging from Early Jurassic to Early Tertiary in this area are essentially the same. A comparison of (La/Yb) _N and (Ce/Yb) _N ratios in the rocks studied with those in oceancrustal basalts shows that the former rocks possess the characteristic values for the rift-geotectonic environment in the studied area.     

Experimental Study on the Effects of Organic Acids on the Dissolution of REE in the Weathering Crust of Granite

The results of REE leached by some organic acids with various concentrations and water/rock ratios for different durations from a mixed samples of the weathering crust of a granite in Gonghe,Guangdong,China,showed that:1)the contents of REE leached increase with increasing concentrations of the organic acids;2) the contents of REE leached by 0.01mol/L organic acids increase with increasing water/rock ration;3) the interaction between the organic acids and the samples enhances the pH value of the medium and the contents of REE leached tend to increase with decreasing pH value;and 4) compared with those leached by ammonia sulfate,the REE leached by the organic acids are characterized by a weaker negative C e anomaly,a stronger negative Eu anomaly,and lower(La/Sm)N and (Gd/Yb)N ratios,indicating that the organic acids have made contributions to the fractionation of REE in the weathering crust.     

Dynamic melting of the Precambrian mantle: evidence from rare earth elements of the amphibolites from the Nellore–Khammam Schist Belt, South India

The Nellore–Khammam Schist Belt (NKSB) in South India is a Precambrian greenstone belt sited between the Eastern Ghats Mobile Belt (EGMB) to the east and the Cratonic region to the west. The belt contains amphibolites, granite gneisses and metasediments including banded iron formations. Amphibolites occurring as dykes, sills and lenses—in and around an Archaean layered complex—form the focus of the present study. The amphibolites are tholeiitic in composition and are compositionally similar to Fe-rich mafic rocks of greenstone belts elsewhere. The NKSB tholeiites show highly variable incompatible trace element abundances for similar Mg#s, relatively constant compatible element concentrations, and uniform incompatible element ratios. Chondrite-normalized REE patterns of the tholeiites range from strongly LREE depleted ((La/Yb) _N = 0.19) to LREE enriched ((La/Yb) _N = 6.95). Constant (La/Ce) _N ratios but variable (La/Yb) _N values are characteristic geochemical traits of the tholeiites; the latter has resulted in crossing REE patterns especially at the HREE segment. Even for the most LREE depleted samples, the (La/Ce) _N ratios are > 1 and are similar to those of the LREE enriched samples. There is a systematic decrease in FeO^t, K₂O and P₂O₅, as well as Ce and other incompatible elements from the LREE enriched to the depleted samples without any variation in the incompatible element ratios and Mg#s. Neither batch and fractional melting, nor magma chamber processes can account for the non-correlation between the LREE enrichment and HREE concentrations. We suggest that dynamic melting of the upper mantle is responsible for these geochemical peculiarities of the NKSB tholeiites. Polybaric dynamic melting within a single mantle column with variable mineralogy is the likely mechanism for the derivation of NKSB tholeiitic melts. It is possible that the NKSB tholeiites are derived from a source with higher FeO/MgO than that of present day ridge basalts.     

Significance of quartz REE geochemistry, Shihu gold deposit, western Hebei Province, North China, using LA-ICP-MS

Rare earth element (REE) geochemistry on monomineral has been widely used in various fields of geosciences to reveal the origin of ore-forming materials and fluid. Quartz are ubiquitous mineral in the Shihu gold deposit that is situated in central shear zone of mesocenozoic Fuping metamorphic core complex in the middle-northern part of Taihang Mountains. Gold-bearing quartz veins are their most important industrial orebodies. Rare earth element abundances in quartz from the Shihu gold mine, as determined by laser ablation-indutively coupled plasma-mass spectrometry (LA-ICP-MS) analysis, are shown to be sensitive to identify barren quartz and mineralized quartz. Amounts of REE concentrations in barren quartz and mineralized quartz are 97 × 10⁻⁹ and 85 × 10⁻⁹, respectively. The average (La/Yb)_N and (La/Sm)_N ratios for the barren quartz are 0.25 and 0.13, and the ratios for mineralized quartz are 0.28 and 0.19, respectively. There is a pronounced positive correlation between (La/Yb)_N and (La/Sm)_N ratios. There is no obvious correlation between REE characteristics and sampling sites. The mineralized quartz show the most pronounced negative Ce anomalies, whereas weak negative Ce anomalies are typical of barren quartz vein. A negative Eu anomaly becomes more significant in mineralized quartz than barren quartz. δCe have a broadly positive correlation with δEu. Y/Ho ratio of barren quartz and mineralized quartz are ranging from 2.14–28.75, and from 1.28–9.92, respectively. The REE characteristics of quartz indicate that the ore-forming fluids of the gold deposit were derived from the deep fluid and its formation was dually controlled by Precambrian metamorphic basement and Mesozoic granitoids. The results significantly enhance the usefulness of quartz in tracing the sources of ore-forming fluid to discuss the genesis of the gold deposit, and as an indicator mineral in mineral exploration in Taihang mountain region.     

Petrogenetic significance of rare-earth element behavior in the basement rocks of southern Obudu Plateau, Bamenda Massif, southeastern Nigeria

Rock samples representing various igneous and metamorphic rocks of southern Obudu Plateau were analyzed for rare-earth element ( REE ) behavior by ICP-MS. Results of the analyses indicate a range of REE abundances and distinctive patterns from highly fraetionated patterns with negative Eu anomalies in granitic rocks to relatively low abundances and less REE fractionated flat patterns with little Eu anomaly in some paragneisses, schists, enderbites and dolerites to unfractionated patterns with positive Eu anomalies in some paragneisses and charnockites. Over all, there are low to high ∑ REE contents with negative to positive Eu anomalies. The ratios of different parameters, especially La/Yb and Ce/Yb, show behaviors consistent with crustal to mantle derivation. The heterogeneity of REE abundances and REE patterns reflects mantle to crustal petrogenetic variations of different rock suites on the Plateau. The LREE content is higher than the HREE content in the highly differentiated rocks, as evidenced by their La/Yb,Ce/Yb and La/Sm ratios, which are normally higher in residual products than in primary melts. The dominantly intermediate nature of the source rock of the orthogneisses is suggested by the generally low ∑ REE. The granites enriched in LREE and depleted in HREE and some of the charnockites with negative Eu anomalies were probably formed by partial melting and crystallization.     

Geochemistry and petrogenesis of granitoids of Lesser Himalayan crystallines,Western Arunachal Himalaya

Low to medium grade crystalline rocks locally known as Bomdila Group extensively covers the Lesser Himalayan region in Western Arunachal Himalaya. This Group consists dominantly of mylonitic gneisses of granitic composition of Palaeoproterozoic age, named as Bomdila mylonitic gneiss (BMG) and a small body of hornblende bearing granite of Mesoproterozoic age known as Salari granite (SG). The BMG is affinity to peraluminous (A/CNK > 1.1) with high content of SiO₂, K₂O/Na₂O ratio, normative corundum, high ratio of FeO^t/MgO in biotite (3.21–5.11) that shows characteristics of S-type granite whereas SG has granodiorite composition with high Na₂O, low K₂O, presence of hornblende, normative diopside, low A/CNK ratio (<1.1) and low FeO^t/MgO ratio in biotite (1.58–1.60) indicates metaluminous I-type granite affinity. The SG has more fractionated nature of REE [(Ce/Yb)_N = 9.06–18.53] and minor negative Eu anomalies [Eu_N/Eu* = 0.69–0.94] as compared to BMG which has less fractionation of REE [(Ce/Yb)_N = 5.95–9.16] and strong negative Eu anomalies [Eu_N/Eu* = 0.37–0.43]. Geochemical and petrological studies suggest that the SG and BMG are not genetically related; SG appears to have derived from igneous source whereas the BMG have been derived from sedimentary source, however these granitoids might have produced during the same thermal event.     

The origin of the acidic and basic rocks of the Tichka Massif,Morocco, based on rare earth elements

The Tichka Massif is one of many late-Paleozoic massifs emplaced in northwestern Africa. It consists of granitic pods surrounded by a complex assemblage of dioritic and gabbroic rocks. Previous workers have suggested an independent origin for the granitic and gabbroic rocks and this study evaluates this suggestion using REE data.The Ce/Yb ratio versus Ce plot for the gabbro shows a large Ce/Yb variation for small changes in Ce, whereas the granites show a linear increase of Ce/Yb with Ce. In the granites, the samples with the highest Ce/Yb ratio have the lowest SiO₂, whereas in the gabbros the Ce/Yb ratio is lowest in the low SiO₂ rocks. The diorites show a tightly clustered pattern.Based on the REE data the granite-diorite-gabbro sequence cannot be related by fractional crystallization. Partial melting of a garnet bearing mantle is consistent with the gabbroic trends. Partial melting of a crustal source with small amounts of apatite and abundant hornblende can produce the granitic rocks.     

Geochemistry of the Archean low- to high-grade transition zone,Southern India

The transition zone between Archean low- and high-grade rocks in southern India represents eroded crustal levels representative of 15–20 km. It is comprised chiefly of tonalitic gneisses with some varieties showing incipient charnockitization and of minor amounts of granitic gneiss and charnockite, both of which appear to have developed from the tonalitic gneisses.Tonalitic gneisses and charnockites are similar in major and trace elements composition while granitic gneisses are relatively enriched in Rb, K, Th, Ba and light rare earth element (REE) and depleted in Cr and Sc. All three rock types exhibit enriched light REE patterns with variable positive Eu anomalies. Total REE content decreases with increasing Eu/Eu and SiO₂ and with decreasing Fe₂O_3T and MgO in the tonalitic gneisses and charnockites.An internally consistent model for the production of the tonalitic gneisses involves partial melting of an enriched mafic source with variable ratios of hornblende to clinopyroxene. This source, in turn, is derived from an ultramafic mantle relatively enriched in incompatible elements. Granitic gneisses form from tonalitic gneisses by alkali metasomatism from chloride-bearing fluids with high H₂O/CO₂ ratios purged from the lower crust by CO₂, and charnockites are produced from tonalitic gneisses (and granitic gneisses) by ischochemical CO₂ metamorphism following the alkali metasomatism.     

Geochemistry and origin of massif-type anorthosites

Samples of Proterozoic anorthosite complexes from the Adirondack Mountains of New York, Burwash Area of Ontario, and the Nain Complex of Labrador, ranging in composition from anorthosite to anorthositic gabbro, have been analyzed for major elements, Rb, Sr, Ba and nine rare-earth elements (REE), in order to set limits on the compositions and origins of their parent magmas. Similar rock types from the different areas have similar major and trace element compositions. The anorthosites have high Sr/Ba ratios, low REE abundances (Ce about 10, Yb about 0.5–1.5 times chondrites) and large positive Eu anomalies. The associated anorthositic gabbros have lower Sr/Ba ratios, REE abundances nearly an order of magnitude higher than the anorthosites, and small to negligible positive Eu anomalies.Model calculations using the adcumulate rocks with the lowest REE abundances and published distribution coefficients yield parent liquids having REE abundances and patterns similar to those of the associated anorthositic gabbros with the highest REE abundances. Rocks with intermediate REE abundances are the result of incorporation of a liquid component by a plagioclase-rich cumulate similar to the adcumulate samples. The analytical data and model calculations both suggest parent liquids having compositions of 50–54% SiO₂, greater than 20% Al₂O₃, about 1% K₂O, atomic Mg/(Mg+Fe²⁺) ratios (Mg No.'s) of less than 0.4, 15–30 ppm Rb, 400–600 ppm Sr and 400–600 ppm Ba, 40–50 times chondrites for Ce and 8–10 times chondrites for Yb.The low atomic Mg/(Mg+Fe²⁺) values for these rocks combined with geophysical evidence suggesting there are not large quantities of ferromagnesian material at depth, indicate that the anorthositic masses are not products of fractional crystallization of mafic melt derived from melting of the mantle. Rather, it is suggested that they are a result of partial melting of tholeiitic compositions at depths shallower than the basalt-eclogite transformation, leaving a pyroxene-dominated residue.     

Rare earth elements in corals from the Isla de Sacrificios Reef,Veracruz, Mexico

Rare earth elements (REE) analysis was carried out in two coral species Diploria strigosa and Copophyllia natans from Isla de Sacrificios Reef (ISR) (19° 10′ 51.6″N; 96° 5′ 45.6″W) Veracruz, Mexico. Both corals were cut at the top, middle and bottom parts to detect possible differences in REE concentrations related to water masses and sediment inputs. An enrichment in heavy rare elements (HREE) compared to light rare elements (LREE) at the top of Diploria strigosa and Copophyllia natans, evidenced by (La/Lu)_SN <0.5, (La/Yb)_SN <0.5 and (Pr/Yb)_SN <0.5 is observed. This HREE enrichment in both corals is probably due to the high pH and CO₃^2? content in the seawater. A negative Ce anomaly is observed throughout Diploria strigosa and Copophyllia natans, probably linked with well oxygenated, highly oxidative modern shallow waters, and high nutrients related to suspended matter. Positive Eu anomalies in both corals are due to development of the ISR in shallow waters. Ce/Ce* vs. (Pr/Yb)_SN diagram suggests the input of terrigenous material, as all samples have Ce/Ce* and Pr/Yb values outside the seawater range signature. However, the Nd/Yb and (Nd/Yb)_SN suggest that the top of Diploria strigosa and Copophyllia natans are associated with coastal waters at about 50 m depth.