含矿岩体和成矿母岩问题

学术界通常认为,岩体有含矿与不含矿之分。含矿岩体与矿床在时间上、空间上和成因上密切相关,是成矿的母岩。认为含矿的热液和成矿金属元素来自岩浆,是岩浆演化分离的晚期从岩浆中分异出来的,属于岩浆期后矿床。笔者的研究表明,花岗质成分的含矿岩体与成矿在时间上和空间上可能有关,但是,不可能成因上有关,含矿岩体也不是成矿的母岩。含矿岩体本质上是一个二元概念,是岩体+蚀变的产物。叠加了蚀变和矿化的岩体就是含矿岩体,没有叠加蚀变和矿化的岩体就是不含矿岩体。花岗质岩浆与热液是两个体系,不是一个体系。成矿所需要的大量的水和金属元素不是来自含矿岩体,而是来自下地壳深部;含矿岩体本身的水和矿化元素也不是来自岩浆,也是来自深部。含矿岩体大体上相当于成矿围岩,不过这个围岩不是沉积岩和变质岩而是花岗岩。实践表明,区分含矿岩体和不含矿岩体从理论上说是不科学的,从方法上说是非常困难的,从找矿实践上说是无益的。笔者指出,虽然含矿岩体存在上述诟病,但是,含矿岩体毕竟是事实,含矿岩体的术语仍然是可以用的,不过,应当重新认识含矿岩体问题,并赋予含矿岩体以新意。     

工程岩体物理场

摘 要　 从岩体的空隙度、强度、变形和渗透性等几个方面说明了岩体的性质受应力状态的 影响情况。这种影响是空间位置的函数‚具有随机场的特点。据此‚提出了工程岩体物理场 的概念。针对岩体性质所具有的这种 “场” 的特点‚认为目前岩体工程中的一些工作方法‚ 如原位试验点的布置、试验数据的统计等‚应相应地作某些改进。 关键词     

吉林红旗岭地区含矿与不含矿岩体的地质地球化学对比

吉林红旗岭地区是我国岩浆型铜镍硫化物矿床的主要矿化集中区之一。在区内已发现的镁铁质一超镁铁质岩体中，有的含有铜镍矿床或铜镍矿化，有的则不含矿。通过本区含矿与不含矿岩体的形成时代、岩石组合、橄榄石矿物成分、岩石化学成分和微量元素组合特征的对比，建立起镁铁质-超镁铁质岩体含镍性的评价标志，为隐伏岩体和新发现岩体含矿性的评价提供了理论依据。     

含矿岩体的评价标志：以太行山北段四个岩体为例

本文以太行山北段四个花岗岩岩体为例，探讨了含矿岩体的评价标志。指出，含矿岩体评价的岩石学、矿物学及地球化学标志。认为，热液脉型矿床的成矿作用直接与岩浆活动密切相关。因此，找矿与岩体的含矿性评价是不可分割的整体。     

宁芜和庐枞盆地含矿岩体地球化学特征对比

宁芜和庐枞盆地是长江中下游地区重要的铁矿产区,两盆地内含矿岩体的岩石学和地球化学特征既具有一定的相似性又表现出一定的差异性。文章对两个盆地内主要含矿岩体的岩相学、主量元素、微量元素、稀土元素、Sr-Nd同位素和锆石Hf同位素等进行对比研究,以期进一步探讨两盆地中成矿岩体的差异。镜下观察结果显示宁芜和庐枞盆地主要含矿岩体具有相同的矿物组合,主量元素特征表明这些岩体具有中硅、富钾和高镁的特点,均为中—基性火成岩。与宁芜盆地含矿岩体相比,庐枞盆地含矿岩体的∑REE、∑LREE和∑HREE含量均较高,明显富集Th、U等大离子亲石元素,具有明显的Eu负异常,说明庐枞盆地含矿岩体的地壳物质较多。两个盆地含矿岩体的Sr-Nd同位素组成指示岩体均来源于富集地幔,庐枞盆地含矿岩体较低的锆石Hf同位素组成说明在岩浆侵入和演化过程中可能有更多的地壳物质加入,导致岩浆的粘稠度降低,更有利于庐枞盆地铁矿的形成。     

铜镍矿床勘查中岩体含矿性的地球化学评价

本文在详细研究铜镍矿床地球化学特征的同时,较系统深入地进行了岩体含矿性研究,较全面地提出了岩体含矿性的定性、定量评价标志及判断矿体剥蚀程度的评价标志,并在应用中取得了较好地质效果.     

两类岩浆的小岩体成大矿

小岩体岩浆矿床作为中国岩浆硫化物矿床的主要类型，越来越受到人们的关注。小岩体成大矿不仅在镁铁-超镁铁岩中如此，在中酸性岩中亦是如此。作者进一步定义了2类岩浆成大矿的小岩体规模即岩体的最大变化截面积可以大到n(n<10) km² ，小到0.00n km²，一般在1 km²左右或更小。提出了2类小岩体成大矿的主要机制和九种成矿类型，镁铁-超镁铁岩是深部熔离-贯入成矿机制（3种类型：深熔-复式贯入，深熔-脉冲式贯入，深熔-单式贯入），中酸性岩是头部气、液、矿质聚集成矿机制（6种类型：前锋式小岩体，斑岩小岩体，夕卡岩-斑岩小岩体，复式斑岩小岩体，单式小岩体，复式小岩体）。强调“小岩体成大矿”对新一轮岩浆矿床勘查具有重要意义，同时指出未涉及或未深入涉及的小岩体成大矿的空间还相当广阔，如铀矿、铁矿、金矿等等，还需要进一步研究和探索。     

大冶铁矿东露天采场边坡岩体力学参数研究

介绍了三十多年来在大冶铁矿东露天采场南、北帮边坡岩体中进行的岩体抗剪强度现场测试方法、技术及试验结果,并汇总出一套历次为边坡稳定性分析采用的抗剪强度参数值,为岩体力学参数数据库增加了大量信息。     

红旗岭―茶尖岭矿带部分含矿岩体时代认识——从陆壳、岩石圈角度认识含矿镁铁-超镁铁质岩体时代

红旗岭―茶尖岭矿带发育镁铁-超镁铁岩体(岩墙群)及铜镍硫化物矿床。关于该矿带含矿岩体时代的观点包括华力西期和印支期。含铜镍硫化物矿床的镁铁-超镁铁岩体(岩墙群)发育要件:初始成熟陆壳、较薄的岩石圈、拉张应力背景,三者缺一不可。只有符合地质事实、符合矿带含铜镍矿镁铁-超镁铁岩体(岩墙群)发育要件的同位素定年数据,才能代表含矿岩体的成岩成矿时代。红旗岭—茶尖岭矿带印支期不具备含矿镁铁-超镁铁岩体(岩墙群)产出的要件。华力西期350Ma,矿带具备红旗岭1号、7号含中、大型铜镍硫化物矿床的镁铁-超镁铁岩体产出的要件,理应代表1号、7号岩体时代;华力西期258Ma,矿带具备茶尖岭包括1号、6号、新6号等含小型铜镍硫化物矿床的镁铁-超镁铁质岩体产出的要件,均代表茶尖岭矿区的镁铁-超镁铁岩体的时代。     

豫西寨凹隐伏岩体对周边银多金属矿的控矿作用

总结了寨凹地区的地质背景、寨凹隐伏岩体的地球物理特征和成矿特征，探讨了该隐伏岩体对区内银多金属矿的控矿作用，建立了成矿模式并指出了找矿方向。     

华北克拉通东缘金岭杂岩体岩浆源区及构造背景:来自岩相学、岩石地球化学及年代学的证据

金岭杂岩体由细粒黑云角闪闪长岩、中细粒黑云角闪闪长岩、中细粒黑云角闪二长闪长岩和细粒角闪二长闪长岩组成,是鲁西地区典型矽卡岩型富铁矿(金岭铁矿)控矿岩体。本次研究对细粒黑云角闪闪长岩和细粒角闪二长闪长岩进行了锆石LA‐ICP‐MS U‐Pb定年,其结果分别为129.2±3.2 Ma和132.8±1.2 Ma,表明该杂岩体的侵位时代为早白垩世。样品SiO2、K2O和Na2O含量分别介于54.17%~63.73%、1.92%~4.76%和3.10%~5.41%之间,K2O/Na2O为0.58~0.94,A/CNK为0.60~0.93,具有轻稀土富集,重稀土亏损的右倾型稀土配分模式,轻、重稀土分馏程度中等((La/Yb)N=9.94~23.49),Eu异常不明显(δEu=0.84~1.10),具中—弱负Ce异常(δCe=0.56~0.92)。样品以富集大离子亲石元素(Ba、K、U、Pb等)、亏损高场强元素(Nb、Ta、Ti)以及高Sr/Y为特征。金岭杂岩体为燕山晚期岩浆活动产物,属准铝质高钾钙碱性系列,岩浆主要来源于富集岩石圈地幔的部分熔融,并在岩浆上升侵位的过程中有地壳物质的同化混染。燕山晚期华北克拉通在古太平洋板块俯冲后后撤引起的板内伸展环境下,增厚陆壳减薄阶段,岩浆上侵就位形成金岭杂岩体。     

西藏日土县拉热拉新花岗岩体特征及构造环境

拉热拉新花岗岩体属于唐古拉-东达山花岗岩带西段羌塘花岗岩区的组成部分,岩石类型主要为黑云角闪闪长岩、黑云角闪石英闪长岩、黑云角闪石英二长岩、黑云花岗闪长岩、黑云二长花岗岩、黑云花岗岩。其地球化学特征表现为：富Si,K,贫Ti,Mg,Fe,Ca,铝饱和指数ACNK〈1．1,稀土元素球粒陨石标准化图式呈右倾斜的“V”字型,LREE富集,HREE相对亏损,铕亏损。其形成时代为早白垩世,为多期次同碰撞的同熔型花岗岩。     

Rare Earth Element and Trace Element Features of Gold-bearing Pyrite in the Jinshan Gold Deposit, Jiangxi Province

<正>Jinshan gold deposit is located in northeastern Jiangxi,South China,which is related to the ductile shear zone.It has a gold reserve of more than 200 tons,with 80%of gold occurring in pyrite. The LREE of gold-bearing pyrite is as higher as 171.664 ppm on average,with relatively higher light rare earth elements(LREE;159.556 ppm) and lower HREE(12.108 ppm).TheΣLREE/ΣHREE ratio is 12.612 and(La/Yb)_N is 11.765.These indicate that pyrite is rich in LREE.The(La/Sm)_N ratio is 3.758 and that of(Gd/Yb)_N is 1.695.These are obvious LREE fractionations.The rare earth element(REE) distribution patterns show obvious Eu anomaly with averageδEu values of 0.664,andδCe anomalies of 1.044.REE characteristics are similar to those of wall rocks(regional metamorphic rocks),but different from those of the Dexing granodiorite porphyry and Damaoshan biotite granite.These features indicate that the ore-forming materials in the Jinshan gold deposit derived from the wall rocks, and the ore-forming fluids derived from metamorphic water.The Co/Ni ratio(average value 0.38) of pyrite suggests that the Jinshan gold deposit formed under a medium-low temperature.It is inferred from the values of high-field strength elements,LREE,Hf/Sm,Nb/La,and Th/La of the pyrite that the ore-forming fluids of the Jinshan gold deposit derived from metamorphic water with ClF.     

Rare earth element signatures of economic and sub-economic porphyry copper systems in Urumieh–Dokhtar Magmatic Arc (UDMA), Iran

A wide variety of porphyry copper deposits have been reported along the Cenozoic Urumieh–Dokhtar magmatic arc in Iran. The formation of these deposits is attributed to closure of Neo-Tethys and the subsequent collisional tectonic regime during the Tertiary. This study presents whole-rock rare earth element (REE) data for the giant to small (Sarcheshmeh, Meiduk, Sungun, Darreh-Zerreshk, Dalli, Iju, Parkam and Ali-Abad) with sub-economic (Daraloo and Reagan) porphyry copper systems. The data indicate a temporal and geochemical evolution from sub-economic porphyry systems to economic deposits. All the economic and sub-economic porphyry copper systems exhibit LREE enrichment relative to HREE, whereas the economic deposits exhibit a relatively steep downward LREE to HREE profile, reflecting higher LREE abundance. The Eu anomalies vary from distinct negative in sub-economic deposits (Eu/Eu* = 0.28–0.70) to either markedly less negative or positive anomalies (Eu/Eu* = 0.45–1.67) in economic deposit. The economic porphyry deposits are characterized by relatively high La/Sm and Sm/Yb values, representing high crustal assimilation in a relatively thickened crust and provide insight into fractionation of hornblende with minor garnet in deep crustal parts (MASH zone). Compared with sub-economic deposits, the steep downward LREE to MREE and flatter to slightly upward MREE to HREE in economic deposits indicate hornblende involvement (magma evolution toward more volatile content). It seems that in an ongoing process of closure of Neo-Tethys, during compression and crustal shortening, the early Eocene–Oligocene sub-economic intrusions are followed by adakite-like hydrous Miocene (and younger) economic Cu-bearing intrusions.     

铜官山地区矽卡岩型铜金矿床稀土元素特征及其成因意义

铜官山地区不同成因类型的矽卡岩发育，各自对应着不同成因类型的铜金矿床，且具有不同的稀土元素分布模式及演化特征，提供了矽卡岩矿床多成因的信息。     

西准噶尔库什库都克石英闪长岩地球化学、年代学及地质意义

库什库都克石英闪长岩位于新疆西准噶尔的达尔布特晚古生代中酸性岩浆岩带中。通过LA-ICP-MS锆石U-Pb定 年,结合锆石阴极发光图像和U、Th元素特征,获得石英闪长岩的年龄为305.3±2.8 Ma（n=19,MSWD=0.17）,时代属晚石 炭世晚期（C2）。石英闪长岩呈半自形不等粒结构,块状构造,矿物成分主要为斜长石、石英、角闪石和黑云母等,局部发 育含柱状辉石的石英辉长闪长岩。岩石的SiO2含量为59.38%~63.37%,全碱变化于6.55%~7.51%;里特曼指数( σ )变化于 2.62~2.88,铝饱和指数(A/CNK值)介于0.83~0.90,为准铝质;岩石轻稀土富集且轻重稀土元素分馏明显,（La/Yb）N 为2.99~ 3.66,负Eu异常（δEu为0.64~0.79）;岩石相对富集Ba、Nd、Zr、K和LREE等元素,而相对亏损Rb、Nb、Th、Sr、P、Ti 和HREE等元素,属高钾钙碱性准铝质I型花岗岩类岩石。石英闪长岩地球化学特征表明其为上地壳变质玄武岩熔融的产 物,在岩浆演化过程中发生了以斜长石、辉石、金红石和磷灰石为主的分离结晶作用,而角闪石基本未发生分离结晶。区 域构造环境演化分析认为西准噶尔不仅在晚石炭世早期存在与俯冲作用相关的岛弧花岗岩,在晚石炭世晚期-早二叠世早 期也存在持续俯冲作用,在此环境下形成了与俯冲作用相关的岛弧型库什库都克石英闪长岩。     

Rare earth element geochemistry and petrogenesis of miles (IIE) silicate inclusions

An ion probe study of rare earth element (REE) geochemistry of silicate inclusions in the Miles IIE iron meteorite was carried out. Individual mineral phases among inclusions have distinct REE patterns and abundances. Most silicate grains have homogeneous REE abundances but show considerable intergrain variations between inclusions. A few pyroxene grains display normal igneous REE zoning. Phosphates (whitlockite and apatite) are highly enriched in REEs (50 to 2000 × CI) with a relatively light rare earth element (LREE)-enriched REE pattern. They usually occurred near the interfaces between inclusions and Fe host. In Miles, albitic glasses exhibit two distinctive REE patterns: a highly fractionated LREE-enriched (CI normalized La/Sm ∼15) pattern with a large positive Eu anomaly and a relatively heavy rare earth element (HREE)-enriched pattern (CI-normalized Lu/Gd ∼4) with a positive Eu anomaly and a negative Yb anomaly. The glass is generally depleted in REEs relative to CI chondrites.The bulk REE abundances for each inclusion, calculated from modal abundances, vary widely, from relatively depleted in REEs (0.1 to 3 × CI) with a fractionated HREE-enriched pattern to highly enriched in REEs (10 to 100 × CI) with a relatively LREE-enriched pattern. The estimated whole rock REE abundances for Miles are at ∼ 10 × CI with a relatively LREE-enriched pattern. This implies that Miles silicates could represent the product of a low degree (∼10%) partial melting of a chondritic source. Phenocrysts of pyroxene in pyroxene-glassy inclusions were not in equilibrium with coexisting albitic glass and they could have crystallized from a parental melt with REEs of ∼ 10 × CI. Albitic glass appears to have formed by remelting of preexisting feldspar + pyroxene + tridymite assemblage. Yb anomaly played an important role in differentiation processes of Miles silicate inclusions; however, its origin remains unsolved.The REE data from this study suggest that Miles, like Colomera and Weekeroo Station, formed when a molten Fe ball collided on a differentiated silicate regolith near the surface of an asteroid. Silicate fragments were mixed with molten Fe by the impact. Heat from molten Fe caused localized melting of feldspar + pyroxene + tridymite assemblage. The inclusions remained isolated from one another during subsequent rapid cooling.     

REE geochemistry of the recent playa sediments from the Thar Desert, India: An implication to playa sediment provenance

The playas (saline lakes) situated in the Thar Desert, north-west India, provide prominent examples of alkaline brine and varying assemblages of detrital and evaporite mineralogy. The eastern margin of the desert is relatively semi-arid, whereas the central to western region is arid to hyper-arid in nature. Rare earth elements (REEs) systematics in the sediments of nine different playas of the Thar Desert were studied to understand the provenance of the sediments and the intensity of chemical weathering in the region. Based on the REE patterns, fractionation of light REE (LREE) (La/Sm)_N and heavy REE (HREE) (Gd/Yb)_N, and Eu anomaly (Eu/Eu*), the upper continental crust normalised playa sediments are divided into two different groups. The eastern margin playa sediments show homogeneous REE contents, relatively positive Eu anomaly and depleted HREE values, whereas the western arid core playa sediments have highly variable REE contents, relatively negative Eu anomaly and similarly fractioned LREE and HREE patterns. The dissimilarity in the degree of HREE fractionations both in the eastern and western playa sediments is attributed to the differential distribution of minerals, depending upon their resistance to chemical weathering. It is believed that the relatively higher abundance of REE bearing heavy minerals and the presence of higher amounts of evaporites influence the large variation of REE distribution and enriched HREE in the western playa sediments. Apart from the relatively higher abundance of heavy minerals, the presence of rock fragments of variable petrographic character and roundness mirror the lower rock–water interaction in the arid western region. The presence of well-rounded metamorphic rock fragments and minerals, sourced from the eastern margin Aravalli mountains, indicates that the playas of the entire desert get the detrital and dissolved material mainly from the Aravalli mountains. Additionally, the western playas receive sediments from their surrounding Proterozoic and Mesozoic formations. This interpretation is supported by the presence of angular rock fragments of basalt, rhyolite and limestone in the western playas.     

渝东南地区石牛栏组稀土元素地球化学特征及地质意义

渝东南地区的下志留统石牛栏组作为重要的油气储集层,研究其古环境变化、物质来源及物源区构造背景具有重要意义。本文采用稀土元素总量w(ΣREE)、REE配分模式、以及w(ΣLREE)/w(ΣHREE)、w(La)_N/w(Yb)_N、w(Ce)_N/w(Yb)_N、w(La)_N/w(Sm)_N、w(Gd)_N/w(Yb)_N、δEu、δCe、Ce_(anom)等特征值研究方法,对渝东南下志留统石牛栏组典型剖面的稀土元素特征及古海洋环境和物源进行深入研究。结果表明:石牛栏组灰岩稀土元素总量略低于大陆地壳平均值,轻稀土较为富集,重稀土亏损,铕明显负异常,铈负异常较微弱。w(ΣREE)证实了石牛栏组的沉积水体由浅缓慢变深再急剧变浅的变化过程。Eu负异常、Ce负异常和C_(eanom)值均揭示石牛栏组沉积时期海水具有弱还原性。REE的分异程度反映了石牛栏组从沉积早期到沉积晚期,沉积速率总体降低。稀土元素的比值特征及w(ΣREE)—w(La)/w(Yb)图解表明其物源源自雪峰山隆起,源岩主要为沉积岩。     

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.