The genesis of lateral accretion deposits in recent intertidal mudflat channels, Solway Firth, Scotland

ABSTRACT The pattern of lateral accretion on an intertidal point bar is a response to the suspended sediment concentrations to which it is exposed. In summer, high sediment concentrations occur only during shallow (ebb) channel flows; deposition therefore takes place mainly on the point bar toe. In winter, high concentrations obtain at all depths and deposition therefore occurs on the upper point bar slopes. Accretion of the point bar toe is limited by scouring resulting from the high rainfall runoff of winter. High suspended sediment concentrations have little effect, however, if flow velocities are too high to allow deposition. Deposition is dependent on the non-uniformity of curved channel flow and is often confined to the downstream (ebb-sense) portion of the point bar. The lateral accretion deposits form a series of wedge-shaped units. Each unit represents one year's deposition, bounded by erosion scarps produced during successive winters. The base of the point bar deposit shows a gradual aggradation, keeping pace with the build-up of the adjacent interchannel flats.     

泥石流堆积物的粒度分布及其分形结构

泥石流堆积物主要由砾石、砂砾、粉粒和粘粒组成,组成泥石流堆积物的颗粒级配变幅很大,从直径大于数十米的巨砾到肉眼难以看见的几微米的胶体微粒均有分布,大小颗粒粒径之比可达106~107。泥石流堆积物颗粒具有明显的自相似性和无标度区间。本文以小江流域多处泥石流堆积物为研究对象,采用图解法全面分析了泥石流堆积物的粒度组成特征,根据分形理论计算了泥石流堆积物颗粒的分维值,对泥石流堆积物的分形特征进行探讨,并与泥石流堆积物粒度特征相联系,发现分维很好的反映了泥石流堆积物颗粒组成及其粒度分布特征。将泥石流堆积物颗粒分维与泥石流的粘性、形成年代等性质相联系,以找出它们彼此之间的关系。     

Fractal-statistical analysis of grain-size distributions of debris-flow deposits and its geological implications

Breakage models and particle analyses have been widely used as tools for describing and interpreting various deposits and providing parameters for assessing the particle-size distribution of the deposits. Debris flows can be seen as a two-phase rheological fluid with a clay-fluid composition, and debris-flow deposits comprise mud, silt, sand, and boulders, with grain sizes ranging from less than one μm to more than several meters. As a consequence, according to fractal theory, the particles in debris-flow deposits have self-similarity in geometrical shape and scale invariance in size. In this paper, the fractal dimensions of particles in various debris-flow deposits are calculated and corresponding fractal features are determined based on fractal-statistical theory. The aims of the study are: to provide a quantitative grain parameter that reflects both the grain composition and grain-size distribution in debris-flow deposits; to compare the fractal dimensions of grains in different types of debris-flow deposits and the degree of self-organization of debris flows; as well as to discuss the geological implications of fractal dimensions and fractal features of particles in debris-flow deposits.     

与火山活动有关的热水沉积锰矿——以贵州二叠纪锰矿为例

贵州产于中二叠统茅口组第二段的锰矿、铁锰矿、含锰菱铁矿,均分布在茅口晚期黔中台沟内。东部遵义一带为碳酸盐锰矿床,西部宣威—水城一带主要为锰帽型次生氧化锰矿床。笔者目的在于探讨黔中台沟锰矿成矿条件,以期扩大找矿远景。研究表明,区内各类锰矿石和矿胚层岩石都是在热水中生成的,证据是：①有大量热水沉积的标志性矿物;②常量、微量元素及稀土元素均具有热水沉积的特征;③流体包裹体均一温度达90～275℃等。锰矿的形成可能与峨眉地幔柱演化的中晚期阶段密切相关。茅口期玄武岩的喷出活动,有利于黔中台沟内硅灰泥锰质组合的形成。东部遵义一带的锰矿,被严格限制在热水喷发形成的硅质角砾岩分布区内,结合其他特征等,说明该区锰矿形成可能与强烈的热水活动有关。     

Sandy-gravelly mass-flow deposits in an ice-marginal lake (Saalian,Leuvenumsche Beek Valley,Veluwe, the Netherlands), with emphasis on plug-flow deposits

In three pits in the Leuvenumsche Beek Valley (near Ermelo and Elspeet), massive and diffusely banded clean gravelly sands, found in association with sandy sediments showing some similarities to the Bouma sequence, were interpreted as originating from sediment gravity flows. The flows, which came to rest on a ca. 6° paleoslope, probably originated from slumping of parts of the ice-pushed ridges at either side of an ice-marginal lake.Major characteristic features in the three sand pits studied are U-shaped channel forms with a maximum depth and width of 10 × 25 rmm. The fills consist of sand and gravels, locally containing giant sand-clasts. The sediments just below the base of these channel-forms are commonly distorted and folded. Especially the massive more sandy fills are surrounded by a finer-grained diffusely bedded and inversely graded zone.These sedimentary features suggest that “rigid” sediment plugs sheared downslope, generating a finer-grained shear zone around the plug scouring a slide scar till its present semi-cylindrical form and preserving the steep sides (exceeding the angle of repose) of the channel-form by “freezing”.The U-shaped channel forms (plugged troughs) are locally overlain by shallower gently sided trough structures, with mainly diffusely banded infillings. Very shallow and often smaller troughs are found again on top of these massive and diffusely banded infillings. The sediments in these troughs consist of repetitions of two types of microsequences: (1) thickly bedded sequences of normally graded massive sands, near-horizontal stratifications, plane beds and cross-bedded sets; and (2) thinly bedded sequences of relatively thick units T_A and thin units T_C and T_D of the Bouma sequence.The repetitions of the microsequences are interpreted as flow pulsations. Upwards thinning of the sequence, together with a finer grain size may point to waning flow conditions. Their association with plugged troughs is suggestive of retrogressive flow-slides.     

Exhalative Sn and W deposits associated with mafic volcanism as precursors to Sn and W deposits associated with granites

Precambrian and Early Palaeozoic submarine exhalative Sn and W deposits are most commonly present in thick deep water sequences comprising pelites, carbonate, calcsilicate and cherty rocks, mafic volcanics and quartz-tourmaline rocks. The exhalative deposits are commonly low grade and, in places, the sequence is transgressed by granites with economic Sn or W mineralisation. These thick deep water sequences as components of sinking trenches are more likely than most other rocks to undergo high grade metamorphism and anatexis. Thus elements such as Sn, W, B, F, Mo, Bi, Li, Be and base metals associated with the exhalites rapidly partition into the anatectic melt, lower the liquidus and solidus, and are concentrated in the late stage aqueous fluids and residual melt fractions to form Sn or W deposits associated with highly fractionated granitic rocks.     

Intrusion-related gold deposits associated with tungsten-tin provinces

An under-recognized and economically important class of intrusion-related gold deposits, which occur within magmatic provinces best known for tungsten and/or tin mineralization, is described with reference to seven major deposits (Fort Knox, Mokrsko, Salave, Vasilkovskoe, Timbarra, Kidston and Kori Kollo). These gold deposits contain a metal suite that includes some combination of bismuth, tungsten, arsenic, tin, molybdenum, tellurium and antimony, and contrasts with that found in the more widely-developed gold-rich porphyry copper and related deposits. The gold deposits associated with tungsten and/or tin provinces are located in cratonic margins, in a landward or back-arc position relative to continental margin arcs (where recognized), or within continental collisional settings. The deposits are related genetically to felsic domes, stocks or plutons of intermediate oxidation state, both magnetite- and ilmenite-series magmas are represented. The intrusion-hosted gold deposits are most commonly of sheeted vein/veinlet type, although greisen-like, disseminated and breccia deposits are also described. Gold may also be concentrated more distally (1–3 km) with respect to the intrusions, where deposits may be of skarn, disseminated replacement or vein types. K-feldspar, albite and/or sericitic alteration assemblages, commonly including carbonate, accompany the gold mineralization. In sheeted vein deposits, alteration is normally restricted to narrow envelopes around veins, whereas more pervasive alteration occurs in greisen-like, disseminated and shallow (<3 km) deposits. The gold mineralization is commonly present with low total sulphide contents (<3%), mainly pyrite and lesser arsenopyrite. In several deposits, bismuth minerals are closely associated with gold, and bismuth-gold and tellurium-gold correlations exist. Most deposits contain tungsten, tin, molybdenum and antimony, although generally these do not correlate with gold; tungsten and molybdenum concentrations may increase with depth or may occur in separate zones. Base metals generally are present in minor amounts (e.g. <100 ppm Cu). The distinct spatial association with felsic intrusions, combined with the consistent metal signature, suggests a magmatic-hydrothermal origin. Fluid inclusions studies indicate the presence of high-salinity fluids in some deposits, and low-salinity and carbonic fluids in most deposits, similar to the composition of fluids in intrusion-related tungsten deposits. Variations in mineralization style largely reflect depth of formation and location relative to the intrusive centre. Several deposits in this class contain >100 tonnes (3 million oz) of gold, thereby highlighting the gold potential of intrusion-related deposits beyond the more traditionally explored gold and copper provinces in arc terranes. Received: 13 March 1998 / Accepted 14 January 1999     

产于钨锡矿区与岩浆作用有关的金矿床

通过七个典型的产于著名钨锡矿讴的金矿床实例，论述了该类金矿床与中度氧化态的花岗岩类有关，其金属组合为Bi,W,As,Sn,Mo,Te,Sb,其产出的大地构造环境包括克拉通边缘、陆缘、弧后盆地或陆陆碰撞带，主要矿化形式表现为脉状至网脉状，亦可见似云英岩化的浸染状和角砾状，其围岩蚀变有钾长石化、钠长石化和绢云母化，其包裹体大多数是低盐度且富合含CO2，但极个别是高盐度的。该类金矿床属贫硫化物型（＜3％），且主要为黄铁矿和毒砂。由于金与铋矿物紧密共性，因此，Au与Bi,Te吴正相关，而通常与W、Sn,Mo,Sb不相关。     

Primary and secondary niobium mineral deposits associated with carbonatites

This work reviews the character and origin of primary and supergene economic deposits of niobium associated with carbonatites. The Brazilian supergene deposits account for about 92% of the total worldwide production of Nb, with the primary St. Honoré carbonatite and other sources accounting for only for 7 and 1%, respectively. The emphasis of the review is upon the styles of Nb mineralization and the geological factors which lead to economic concentrations of Nb-bearing minerals. Primary economic deposits of Nb are associated principally with carbonatites found in diverse types of plutonic alkaline rock complexes. Primary magmas are principally those of the melilitite, nephelinite and aillikite clans. Although many primary niobium deposits are associated with carbonatites, ijolites and syenites in the same alkaline complexes can also contain significant Nb mineralization in the form of niobian titanite and diverse Nb–Zr-silicates (marianoite-wöhlerite); these potential sources of Nb have not as yet been explored or exploited. Primary Nb deposits can be regarded as large tonnage, low grade (typically < 1 wt.% Nb₂O₅) disseminated ore deposits. Niobium is hosted principally by diverse Na–Ca–U-pyrochlores, ferrocolumbite and fersmite. Every actual, and potential, primary Nb deposit is unique with respect to the varieties of pyrochlore present; extent of replacement by other minerals; and degree of alteration by deuteric/hydrothermal fluids. Within a given occurrence individual petrographically-defined units of carbonatite contain distinct suites of pyrochlore. Bulk rock analysis for Nb gives no indication of the style of mineralization and provides no information of use regarding beneficiation of the ore. Evaluation of any Nb deposit requires extensive definition drilling and detailed mineralogical studies. Primary Nb deposits result from the early crystallization of Nb-bearing minerals in magma chambers followed by crystal fractionation, magma mixing, and redistribution of Nb-minerals by density currents. Supergene Nb deposits occur in laterites formed by extensive weathering of primary carbonatites. The process results in the decomposition of apatite and magnetite, removal of soluble carbonates and physical concentration of resistant primary pyrochlore. Intense lateritization results initially in the replacement of primary pyrochlores by supergene, commonly Ba, Sr, K or Pb-bearing pyrochlores, and ultimately complete decomposition of pyrochlore and formation of Nb-bearing rutile, brookite, and anatase. The Nb contents of the laterites can be enriched up to 10 times or more above those of the primary carbonatite. Commonly, pyrochlores in laterites are fine grained and intimately intergrown with hematite, goethite and minerals of the crandallite group. The different styles of mineralization of primary and secondary Nb deposits require different methods of ore beneficiation.     

一个与火山碎屑岩和热液喷发有关的金矿床

泥堡金矿位于黔西南峨眉山玄武岩外缘的凝灰岩分布区,属微细浸染型矿床。文章通过对泥堡矿床的地层、岩石、构造、矿体、矿石等实地调查和综合解析,探讨其主要控矿因素和成矿作用,为今后寻找类似矿床提供参考和借鉴。研究结果表明,泥堡矿床最主要的金矿体产于茅口组与峨眉山玄武岩组之间的沉积间断面附近,是一个集矿源层、流体通道和容矿部位于一体的极具特色的成矿组合。在该区,P2-3β1-1底部富含有机质的凝灰岩,P2-3β1-1与大厂石英岩之间的热液喷发角砾岩,都是最主要的赋矿部位和容矿岩石。各种同位素和流体包裹体测试结果显示,黄铁矿中的硫与玄武岩中的硫可能都来自幔源;富含Si O2和K的低盐度、中低温成矿流体是地表水沿断裂深循环形成的;成矿时代属晚侏罗世(142Ma),是黔西南地区最早形成的金矿床之一。     

Geochemical alteration associated with the Selbaie copper-zinc-silver deposit

The object of this study is to establish the nature of geochemical alteration in the wall rocks of the Selbaie Cu-Zn-Ag deposit, and to ascertain whether bedrock geochemistry could be applied in exploration for deposits of this type. The Selbaie Cu-Zn-Ag deposit, in northwestern Quebec, is atypical of base-metal deposits in the Canadian Shield, as mineralization occurs in epigenetic veins and as disseminations in volcanic wall rocks, rather than as syngenetic massive sulfide bodies which have been the focus of extensive comparable studies in the past. The deposit comprises three mineralized zones in felsic tuffs and quartz porphyry. Two of these, the A1 and A2 zones, which are the focus of the present study consist of quartz-carbonate veins containing chalcopyrite, sphalerite, and pyrite, and accessory sulfide minerals. The B zone is not considered in this study. Samples of drill core were collected from sections crossing the A1 and A2 zones and analyzed for total Si, Al, Fe, Mg, Ca, Na, K, Ti, Mn, P, and S by X-ray fluorescence, and for aqua-regia-extractable Cu, Zn, Ni, Pb, Fe, and Mn by atomic absorption. Although the distribution of individual element concentrations is clearly related to bedrock type, rocks proximal to mineralization have higher SiO₂, Fe₂O₃, Cu, Zn, Fe, and S contents, and lower Al₂O₃ and K₂O contents, than rocks more distal from mineralization. MgO content shows an irregular distribution and may also increase toward mineralization. CaO and Na₂O contents are very low in all pyroclastic rocks.In order to take into account the effect of bedrock type, linear regression analysis was performed on the data to estimate the normal concentration of individual elements using SiO₂ contents as the predicted variable. Spatial distributions of residual values of element concentrations indicate that rocks close to mineralization have higher residual Fe₂O₃, Cu, Zn, Pb, and Fe contents, and lower residual Al₂O₃ and K₂O contents, compared to rocks more remote from mineralization. These distribution patterns are clearer than in the case of the single-element data but variations between element responses still exist in some instances. In an attempt to overcome the variation in patterns revealed by some element distributions, discriminant analysis was undertaken to see whether mineralized areas could be distinguished on the basis of an element association. Discriminant functions were calculated for data from areas adjacent to mineralization, and from areas remote from mineralization. Areal distribution of discriminant scores outlined an anomalous area extending up to 200 m beyond the mineralization. Petrographic studies of selected samples correlated high SiO₂ and low Al₂O₃ content with silicification in the most altered rocks adjacent to mineralization. High Fe₂O₃, MgO, and extractable Fe concentrations were found to occur in chlorite- and carbonate-rich zones. Samples rich in S, Cu, Zn, and b, and to a lesser extent Fe, were characterized by the presence of sulfides. High concentrations of Al₂O₃ and K₂O relative to that of SiO₂ are typical of sericitization. On this basis, the results demonstrate that anomalously high or low concentrations of element associations, revealed by discriminant analysis, occur in large coherent zones exceeding the size of the deposit. The procedure is potentially useful as an exploration guide for epigenetic disseminated and vein-type base-metal styles of mineralization as well as the syngenetic massive sulfide type of deposits that have been extensively studied in the past.     

Structural types of ore deposits associated with volcanic necks

Volcanic necks, with or without caldera, are classified into several subtypes, depending on shape, structure, genesis, differentiation, tectonics and other characteristics of the fillings, with attention to the associated orefields (if any), ore bodies or veins, and the kind of mineralization, such as U (± F), U-Mo, Au-Ag, Hg, F (± B), B-Sn (± Ag), Cu-B, polymetallic (± F), carbonatite-rare metals, hematite-magnetite, with examples drawn from different parts of the world. – IGR Staff.     

Borosilicate alteration associated with U-Mo-Zn and Ag-Au-Zn deposits in volcanic rocks

Borosilicate alteration is developed in many uranium-molybdenum-zinc deposits in volcanic piles such as at Novazza (Italy), Novoveska Huta (Slovakia), Ben Lomond (Queensland, Australia), the Saar-Nahe basin (Germany), the Shengyuan district (China), and at many deposits in Russia. These uranium-molybdenum-zinc deposits share similar styles of alteration with silver-gold-zinc deposits in volcanic rocks, like those of the Humboldt Range (Nevada, USA), the Basin district (Montana, USA) and Equity Mine (British Columbia, Canada). In thick volcanic piles, fluid-rock interaction commonly develops under the influence of convective hydrothermal systems. In borosilicate-bearing systems the alteration is characterized by changes in borosilicate mineralogy and chemistry under mesothermal conditions. Zonal distribution of different compositions of tourmaline can be observed including regular increases of alkali deficiency in the X(3a) site from peripheral (chlorite-epidote-prehnite) to internal (sericite and/or pyrophyllite) alteration zones. In the central part of these systems tourmaline is absent and the alteration assemblage is characterized by an andalusitedumortierite-quartz association. Such changes in mineral assemblage are related to an increase in temperature from 250 to 350–400 °C and to decreases in pH and Eh, from the outer toward the inner parts of the hydrothermal system. The zonation of the borosilicate-bearing alteration systems is similar to that of aluminosilicate-bearing hydrothermal systems (muscovite, pyrophyllite, andalusite) developed in volcanic rocks. A kaolinite-alunitejasperoid assemblage is generally associated with the borosilicate alteration, and seems related to a late hydrothermal phase mainly located in graben structures.     

Ore deposits associated with mafic magmas in the Kaapvaal craton

Mafic and ultramafic magmatism played an important role in the 3.5 Ga long history of the Kaapvaal craton. The oldest (3.5 Ga) greenstone belts contain mafic and ultramafic volcanics that erupted in an oceanic environment, probably in oceanic plateaus. Then followed a series of continental flood basalts, from the ∼3.4 Ga old Commondale and Nondweni sequences, to the 180 Ma Karoo basalts. The history was dominated, however, by the emplacement, 2.1 Ga ago, of the Bushveld complex, an enormous layered ultramafic-mafic-felsic intrusion. Three types of ore deposits might be found in such a sequence: Ni-Cu-Fe sulfides in komatiites of the greenstone belts; “Noril'sk-type” Ni-Cu-PGE deposits in the Karoo and other flood basalts; and deposits of Cr, platinum-group elements (PGE) and V in the Bushveld and other layered intrusions. Only the latter are present. It is tempting to attribute the absence of komatiite-hosted deposits to the specific character of the ultramafic rocks in Kaapvaal greenstone belts, which are older that the 2.7 Ga komatiites that host deposits in Australia, Canada and Zimbabwe, and are of the less-common “Al-depleted” type. However, a review of mantle melting processes found no obvious connection between the character of the mantle melts and their capacity to form ore deposits. The lack of this type of deposit may be due to differences in the volcanic environment, or it may be fortuitous (the Barberton and other belts are small and could fit into deposit-free parts of the much larger Australian or Canadian belts). Still more puzzling is the absence of Noril'sk-type deposits. The Karoo and older flood basalt sequences appear to contain all the important elements of the volcanic sequences that host the Siberian deposits. It is now recognised that these deposits formed through the segregation of sulfide from magma flowing rapidly through conduits en route from deeper magma chambers to the surface. An exploration approach aimed at understanding the fluid dynamics of such systems seems warranted. Although the Bushveld intrusion has been studied for decades and its deposits are taken as type examples of magmatic mineralisation, the origin of its PGE deposits remains unclear. Opinion is divided on the relative importance of sulfide segregation from magma filling a large chamber at the time of emplacement, and the scavanging of PGE from fluids circulating through cumulates at a late magmatic stage. Answers to these questions may come from studies designed to gain a better understanding of the mechanisms through which the magma chamber filled and solidified. Received: 15 September 1996 / Accepted: 7 January 1997     

Vertical accretion of flood deposits and deeply stratified archaeological site formation in Central Maine,USA

Investigation of deeply stratified archaeological sites on the Piscataquis River in central Maine has revealed a continuous sequence of human occupation from ca. 10,000 yr B.P. to the near present. As an integrated aspect of the archaeological excavations, geomorphic features and surficial deposits were mapped from aerial photographs and field checked. Stratigraphic profiles were recorded from various locations and sediment column samples were collected and analyzed for grain size distribution in 1-cm vertical intervals from a 3-m deep excavation at the Sharrow site (ME 90-2D) to examine the flood deposits. Results include a general chronology of fluvial processes of the Piscataquis River since deglaciation and evidence of dominant vertical accretion of flood sediments on floodplain terraces throughout the Holocene epoch. This article defines an archaeologically significant but rarely recognized depositional regime characterized by a laterally controlled river channel and the exclusive vertical accretion of flood sediments. © 1994 John Wiley & Sons, Inc.     

Phosphate-rich deposits associated with the Mio-Pliocene unconformity in south-east Australia

Phosphates are present on the surface of the Mio-Pliocene unconformity in the Otway, Port Phillip and Gippsland basins of south-east Australia. The phosphates occur as lenticular lag deposits and include reworked phosphatic intraclasts, vertebrate bone and teeth. In situ phosphatized burrows are also found in sediments of Late Miocene and Early Pliocene age. The phosphatic intraclasts on the unconformity are interpreted as reworked phosphatized burrows derived from latest Miocene sediments (6 to 5 Ma). The phosphatization of these intraclasts is temporally related to the unconformity. The timing of phosphogenesis coincides with a period of transgression across the south-east Australian margin following Late Miocene uplift. This transgression is responsible for initial marine erosion of the underlying Miocene sequence, creation of a period of very slow sedimentation that was favourable to phosphate formation and subsequent deposition of the latest Miocene through to Pliocene sediments. The continental weathering of the uplifted highlands adjacent to the sedimentary basins, global phosphorus enrichment in the Late Miocene oceans and localized upwelling may all have contributed to phosphatization in south-eastern Australia.     

石膏矿床的地质特征及对硫化矿床的指示意义

从研究划分石膏矿化的成因类型入手,进行热液化学成分来源分析和岩石蚀变分带研究,结合典型矿床实例分析,总结出在碳酸盐岩中出现热液交代型石膏矿化体附近,往往伴生有金属硫化矿体或含硫化矿物丰富的岩石,该规律对寻找硫化物型金属自矿体的意义巨大.     

斜长岩体中Fe-Ti-P矿床的特征与成因

岩体型斜长岩为由90%以上斜长石组成的岩浆岩,具变压结晶的特点,仅形成于元古宙(2.1～0.9Ga),常赋存有Fe-Ti-P矿床。Fe-Ti-P矿体既呈整合层状也呈透镜状和席状等不规则形式产出;矿石类型有块状和侵染状,前者矿石矿物含量>70%,后者矿石矿物含量为20%～70%;矿物组成上,不同矿床稍有差别:部分矿床的Fe-Ti氧化物以钛磁铁矿为主、钛铁矿次之,而其他矿床则以赤钛铁矿为主、磁铁矿次之。一些矿床磷灰石含量较高,出现仅由Fe-Ti氧化物和磷灰石组成的铁钛磷灰岩。研究表明,Fe-Ti-P矿床由富Fe、Ti的岩浆演化形成,其母岩浆是在深部岩浆房中大量结晶斜长石后的残余岩浆。部分学者认为不同矿石经正常的结晶分异作用并堆晶形成,但该机制很难解释呈不规则状产出的矿石;其他学者则认为不混熔作用对矿石的富集(尤其是脉状、席状的铁钛磷灰岩)有重要作用,但该机制缺乏岩相学和地球化学方面的证据。河北大庙Fe-Ti-P矿体呈透镜状、席状等不连续地分布于斜长岩中,矿体不发育明显岩浆分层,但仍出现不同矿石的相带。依据详细的岩相学、矿体中矿物含量和成分的变化规律以及全岩地球化学特征,我们判断大庙矿床中不同矿石为堆晶矿物和晶隙流体的混合产物,它们由铁闪长质岩浆经结晶分异和堆晶作用形成,与不混熔作用关系不大。矿体不规则状产出的特点可能与岩浆动力分异作用有关,并伴随有小范围的亚固相迁移。