内蒙古金矿床的成因类型划分

将内蒙古已知金矿划分为5大类型20个矿床亚类：即重熔岩浆热液金矿、变质热液金矿、沉积变质热液金矿、火山-次火山热液金矿、砂金矿。对各类型金矿床的地质成因特征进行了初步探讨。     

内蒙古金矿床的成因类型划分

将内蒙古已知金矿划分为5大类型20个矿床亚类:即重熔岩浆热液金矿、变质热液金矿、沉积变质热液金矿、火山-次火山热液金矿、砂金矿.对各类型金矿床的地质成因特征进行了初步探讨.     

冀东地区金矿地质特征及其成因

讨论了冀东地区已知金矿类型及其地质特征、矿体分布规律及其成因,并与印度的科拉尔金矿作了对比。认为冀东地区的金矿不是典型的绿岩型金矿,而是与基性火山岩有成因联系的沉积变质-变质热液-重熔岩浆热液等不同成因类型的金矿床。     

沂水县王家庄子矿区金矿床地质特征

沂水县王家庄子金矿处于沂水汤头断裂带中段东侧,矿体赋存于其次级EW向和近SN向断裂构造中,赋矿围岩为紫苏花岗闪长岩和二长花岗岩。矿床成因类型为中低温重熔岩浆热液型金矿。     

山东省莱州市三山岛金矿床地质特征及成因探讨

莱州—招远地区是我国最重要的金矿资源基地,截止目前已发现的各类金矿床（点）200余处,其中大、中型金矿床20余处,已探明的储量占全国的1/4.三山岛金矿床是区内著名的“焦家式”金矿的典型代表之一.文章通过对三山岛金矿床地质特征研究表明,矿体地质特征与控矿断裂构造特征相一致,矿床成因属于重熔岩浆期后中温热液交代矿床.     

山东西直格庄金矿矿床地质特征及其找矿指示意义

本文在区域成矿地质背景的基础上,详细论述了西直格庄金矿的控矿断裂特征、矿体地质特征和矿石特征及矿物成分等,并划分出4个蚀变矿化阶段。通过矿化类型、矿物组合等研究确定西直格庄金矿成因类型属于交代—重熔岩浆期后中低温热液沿破碎带交代型金矿床。通过金矿床成矿规律的分析进一步提出地层、岩性、构造、围岩蚀变等方面是该金矿深部及外围的找矿标志及方向。     

五龙金矿成因研究

五龙金矿是一大型脉状金矿床,金矿化与燕山期构造-岩浆活动密切相关,野外地质特征及大量岩石化学、地球化学及同位素资料表明,三股流岩体、脉岩和含金石英脉是古老含金矿源层重熔的产物,三者具有相同的来源。矿床成因类型为重熔岩浆热液金矿床。     

玲珑花岗质杂岩体形成的物理化学条件及其地质意义

胶东西北部是我国金矿的重要产区,招掖金矿带的形成与玲珑花岗质杂岩有密切的成因联系。玲珑花岗质杂岩是一个多期次形成的复式岩体,最终定位于燕山期。它主要由云山、崔召、玲珑片麻状花岗岩、郭家店（型）、郭家岭（型）岩体组成。本文研究了上述诸岩体形成的Ｔ、ｐ、ｆＯ２、ｆＨ２、ｐＨ２Ｏ条件及熔浆中的含水量。通过玲珑花岗质杂岩形成的物理化学条件研究得出：玲珑花岗质杂岩即不是区域变质作用中混合岩化的产物,也不是幔源岩浆分异、冷凝的产物,而是由太古宙、元古宙变质岩重熔交代所形成的原地半原地型花岗质杂岩体。玲珑花岗质杂岩,尤其是郭家岭型花岗岩对本区金矿的形成具有重要意义。重熔岩浆作用,热驱动下流体循环和含矿热液中水的浓缩（收缩）,是胶东金矿得以形成的主要原因。     

雪峰弧形构造带中段天明金矿地质特征及找矿标志

湖南省安化县天明金矿地处江南造山带雪峰弧形构造带中段,金矿成矿地质条件优越。在综合研究区域资料和勘查成果的基础上,根据地球物理、地球化学、遥感等地质资料,对比分析了天明金矿与邻区典型金矿的成矿地质环境、矿体展布、矿石特征及矿床成因特征,探讨了天明地区的成矿地质条件和找矿标志,并初步建立了天明地区金矿的成矿模式和综合找矿模型。天明金矿目前已揭露3条近EW向的破碎蚀变带,其成因类型为造山与重熔岩浆热液混合型金矿,且在垂向分带上显示出石英脉型—构造蚀变岩型的分带特征。研究成果可以为天明金矿及同类型金矿的找矿工作提供参考。     

桂东地区金矿硫同位素地质特征及找矿意义

桂东地区发育三种成因类型的金矿,各类金矿的硫同位素组成有明显差异。本文计算了共生硫化物沉淀时的同位素平衡温度,并根据各类金矿的硫同位素组成特征,探讨了硫的来源,认为硫源应以深源重(同)熔岩浆热液为主,部分来自地层。同时还研究了硫同位素组成的空间变化规律及对矿床深部及外围的找矿意义。     

Structure and organization of submarine basaltic flows: sheet flow transformation into pillow lavas in shallow submarine environments

Distal pillows occur associated with a sheet flow and megapillows in the me?akoz outcrops of the Basque–Cantabrian Basin (N Spain). Basaltic volcanic rocks are interbedded with Turonian sediments and depict typical features of shallow submarine emissions. An exceptional basaltic flow displays four types of morphology: (1) sheet lava with columnar jointing, (2) welded columnar breccia, (3) megapillows, and (4) pillow lavas with sparse megapillows. The field data from me?akoz combined with experimental and field data from the literature for similar volcanic facies can be integrated into a new propagation model for the transition from sheet flows to pillow lavas in underwater environments. At near vent high emission rates, lava flows develop a thin crust immediately after its emplacement and break at the front under the magma pressure allowing for the massive propagation of lava as a sheet flow. Increased cooling promotes thickening of the lava outer crust far from the vent while continuous supply of fresh magma increases the pressure onto the thick crust until its rupture. The lava emitted in small volumes from the flow front promotes the formation of megapillows and pillow lavas that are later on covered by the advancing sheet flow. The lava flow freezes progressively toward more distal parts, gradually increasing its viscosity until it stops. The crust temporarily holds the residual melt pressure increasing the volume of the flow distal section by inflation. Finally, the internal magma pressure breaks the crust and liberates lava at moderate-to-low flow rates producing pillows, while lava drainage inside the inflated sheet flow produces lava tunnels and gravitational collapse of the roofs by hydrostatic pressure to form breccias nurtured by columnar lava fragments.     

松辽盆地营城组火山岩冷却单元及地层结构分析

火山岩冷却单元的识别是火山岩地层和岩相研究的重要环节。松辽盆地东南缘露头区和徐家围子断陷营城组火山岩剖面的剖析显示,冷却单元主要存在4种主要的单元类型:碎屑岩型、熔岩型、碎屑岩+熔岩型和熔岩+碎屑岩型。碎屑岩型和熔岩型是端元类型,分别反映蒸汽喷发和岩浆喷发的作用过程;碎屑岩+熔岩型是基本组合单元类型,反映蒸汽-岩浆喷发的连续作用过程;熔岩+碎屑岩型属于改造的或特殊机制的类型。冷却单元本身及其堆叠具有相的意义,是火山岩地层的基本成因地层单元,因此成为解释火山岩地层结构、了解形成与保存过程的重要基础。通过火山岩冷却单元识别与叠置分析,构建了松辽盆地徐家围子断陷营城组一段的地层结构。     

浙江新昌早白垩世复合岩流中的岩浆混合作用

浙江新昌拔茅地区早白垩世复合岩流中各种火山岩（Ｒｂ－Ｓｒ等时线年龄为９６．３Ｍａ）属高钾钙碱性岩系，在其中发现了中生代火山活动中岩浆混合作用的确凿证据，岩相学及地球化学研究表明，这种复合岩流中的安山质岩浆是由同时代橄榄拉斑玄武岩浆和流纹岩浆相互混合而形成的。     

Crystal Clusters, Feldspar Glomerocrysts, and Magma Envelopes in the Atascosa Lookout Lava Flow, Southern Arizona, USA: Recorders of Magmatic Events

The Atascosa Lookout trachyandesite lava flow is the youngestand most compositionally primitive unit in the middle TertiaryAtascosa–Tumacacori–Cerro Colorado volcanic complex(ATCC). The flow hosts a variety of objects of contrasting origin,including (1) clusters of plagioclase ± chromian diopside,magnesian augite, quartz, hornblende, and orthopyroxene; (2)amoeboid-shaped quartz-bearing enclaves; (3) plagioclase crystalswith a concentric interior zone of small melt inclusions (dustyplagioclase); (4) plagioclase crystals with cores filled withlarge melt inclusions (honeycomb plagioclase); (5) plagioclaseglomerocrysts. The groundmass of the trachyandesitic flow istrachydacite. Some crystal clusters, enclaves, and plagioclaseglomerocrysts are surrounded by diffuse envelopes of trachydacitehigher in K and Mg and lower in Si than the trachydacitic groundmassof the flow. This envelope material is interpreted as foreignmagma that engulfed these objects as it invaded their host magma.Both the crystal clusters and plagioclase glomerocrysts maybe the remains of cumulate crystal layers, disrupted by influxesof magma into their reservoirs. Crystals in the lava flow originatedin at least three distinct magmas and their hybrids. The groundmassof the lava flow preserves evidence for repeated infusion ofenvelope magma into the system. These influxes fueled the invasionof crystal clusters, plagioclase glomerocrysts, enclaves, andswirls of the envelope magma into the groundmass of the AtascosaLookout lava flow. Despite the compositional and textural varietyapparent in the lava flow, the magmas involved in its developmentmay have been genetically closely related. The collection offeatures in the lava flow resulted from the development of compositionallayers in the magma, accumulation of crystal-rich horizons,disturbance of the system by repeated magma influx, and minorcrustal assimilation. KEY WORDS: crystal clusters; enclaves; glomerocrysts; trachyandesite     

长英质富晶体火山岩成因——岩浆补给与晶粥再活化

火山是人类窥探深部岩浆系统的窗口。从全球范围来看,贫晶体富熔体的火山岩(尤其是玄武岩和流纹岩)大面积出露,而富晶体的长英质火山岩仅出露于破火山周围。长英质富晶体火山岩主要可分为两类：一类是成分和晶体含量均一的火山岩;另一类是成分和斑晶含量分带的火山岩。富晶体火山岩是冷储存晶粥接受岩浆反复补给后重熔、再活化,重新具备流动能力而喷发形成的,储库中先存物质的成分决定了再活化形成的富晶体火山岩的类型。富晶体火山岩的存在能够很好地解释岩浆储库具有较长的寿命而岩浆汇聚结晶的过程却是迅速的这种看似矛盾的现象。虽然近年来长英质富晶体火山岩的研究已经取得了明显的进展,但仍有许多问题亟待解决,如碎斑熔岩的成因,如何判别晶粥活化,晶粥再活化与火山喷发的关系,岩浆补给和晶粥活化的时间尺度等。对富晶体火山岩的进一步研究将有助于深入揭示熔体演化、运移、在浅部的聚集和喷发的机制,并可为建立更完善的长英质岩浆演化模型提供更多信息。     

Syn-eruptive breakdown of pyrrhotite: a record of magma fragmentation,air entrainment,and oxidation

Air entrainment in fragmented magmas controls the dynamics of volcanic eruptions. Pyroclast oxidation kinetics may be applied to quantify the degree of magma–air interaction. Pyrrhotite (Po) in volcanic rocks is often oxidized to form magnetite (Mt) and hematite (Hm), and its reaction mechanisms are well constrained. To test utilizing Po oxidation as a marker for magma–air interactions, we compared the occurrence of Po oxidation products from three different eruption styles during the Sakurajima 1914–1915 eruption. Pumices from the Plinian eruption include columnar-type Fe oxides (Mt with subordinate width of Hm) often accompanied by relict Po. This columnar type is also found in clastogenic lava, where it is almost completely oxidized to Hm. The effusive lava contains framboidal aggregates of subhedral to anhedral Mt crystals without Hm. The formation mechanisms of columnar and framboidal Fe oxides were estimated. The columnar type Fe oxides were formed syn-eruptively through gaseous reactions, as opposed to the melt in a magma chamber, as demonstrated by the Ti-free nature of the columnar Mt and its synchronous oxidation to Hm. By contrast, the framboidal type was formed in a melt with decreasing fS₂. The calculation of Hm growth in a conductively cooling pumice clast constrains the surface temperature of pumice in the eruption column. The paragenesis and oxidation degree of Po and Fe oxides are consistent with the eruption processes in terms of magma fragmentation, air entrainment, and welding, and can, therefore, be a responsive marker for the magma–air interaction.     

深层火山碎屑熔岩形成机理及其指相意义研究:以松辽盆地庆深气田为例

基于不同岩性、岩相条件从根本上决定了储集空间的发育程度与规模,所以找火山岩的储层集中表现为火山岩相、亚相的识别。文中以松辽盆地庆深气田为例,重点研究了深层火山碎屑熔岩形成机理及其在火山岩地质相和测井相识别中的意义。研究表明,火山碎屑熔岩类火山岩常见火山碎屑流、泡沫熔岩流、岩流自碎作用、近地表隐爆作用、再熔结(胶结)型5种成因类型,且不同成因火山碎屑熔岩具有明显不同的矿物岩石学特征和测井响应特征。根据其形成机理、矿物岩石学特征和FMI成像特征,认为上述5种成因类型的火山碎屑熔岩分别发育于爆发相热碎屑流亚相、介于爆发相和喷溢相之间的爆溢相、喷溢相、火山通道相隐爆角砾岩亚相、火山通道相火山颈亚相或近火山口相。该研究成果对于促进火山岩相、亚相的准确识别和优质储层的有效预测具有重要的指导意义。     

云南大红山哈母白祖熔岩铁矿矿床地质特征及成因探讨

哈母白祖熔岩铁矿位于大红山铁铜矿区东部.矿体均赋存于大红山群红山组变钠质熔岩、绿片岩中,呈层状、似层状、透镜状产出,矿石以磁铁矿为主。矿床的形成与古元古代的海相基性岩浆喷发作用关系密切,具有火山喷溢和火山喷发沉积的特点,后期又经历了区域变质作用的改造,是经过多次地质作用而形成的多成因复合型矿床,成因类型初步判断为火山岩浆喷溢-喷发沉积-变质改造复合成因矿床。     

金星薄饼状火山类比研究

金星薄饼状火山(陡边火山)是一类形貌非常独特的火山,有别于太阳系中其他的火山:近圆的底面轮廓、平坦的顶部和较大的顶底直径比.薄饼状火山被认为是高黏度岩浆喷发形成的,但是这一成因并不被广泛接受.火山的形貌特征主要取决于岩浆成分、喷发机制、重力和喷发环境(如大气压)等.因此,通过对比地球火山的形貌特征及形成机制可以为金星薄饼状火山的成因提供指示.我们利用底面不规则度(ii )、高径比(H/W B )、顶底直径比(W S/W B )、侧边最大坡度处的标准化高度(HS m a x )、顶部高径比(H S/W S )和喷发量(V )这些形貌参数定量地将地球表面的复式火山、盾形火山、火山锥、熔岩穹丘(Peleean 型和 Coulees 型)、海底平顶火山以及泥火山的形貌特征与金星薄饼状火山对比.Coulees型熔岩穹丘、海底平顶火山和泥火山的形貌特征与金星薄饼状火山有一定的相似性.Coulees型熔岩穹丘剖面形态与薄饼状火山最为相似,可能指示了薄饼状火山具有类似的成因机制,而海底平顶火山侧边的上凹特征可能指示了其与薄饼状火山完全不同的成因机制.因此,薄饼状火山可能是相对高黏度的岩浆以较高速率持续性喷发形成.     

The Petrology and Geochemistry of Oto-Zan Composite Lava Flow on Shodo-Shima Island, SW Japan: Remelting of a Solidified High-Mg Andesite Magma

The Oto-Zan lava in the Setouchi volcanic belt is composed ofphenocryst-poor, sparsely plagioclase-phyric andesites (sanukitoids)and forms a composite lava flow. The phenocryst assemblagesand element abundances change but Sr–Nd–Pb isotopiccompositions are constant throughout the lava flow. The sanukitoidat the base is a high-Mg andesite (HMA) and contains Mg- andNi-rich olivine and Cr-rich chromite, suggesting the emplacementof a mantle-derived hydrous (7 wt % H₂O) HMA magma. However,Oto-Zan sanukitoids contain little H₂O and are phenocryst-poor.The liquid lines of descent obtained for an Oto-Zan HMA at 0·3GPa in the presence of 0·7–2·1 wt % H₂Osuggest that mixing of an HMA magma with a differentiated felsicmelt can reasonably explain the petrographical and chemicalcharacteristics of Oto-Zan sanukitoids. We propose a model wherebya hydrous HMA magma crystallizes extensively within the crust,resulting in the formation of an HMA pluton and causing liberationof H₂O from the magma system. The HMA pluton, in which interstitialrhyolitic melts still remain, is then heated from the base byintrusion of a high-T basalt magma, forming an H₂O-deficientHMA magma at the base of the pluton. During ascent, this secondaryHMA magma entrains the overlying interstitial rhyolitic melt,resulting in variable self-mixing and formation of a zoned magmareservoir, comprising more felsic magmas upwards. More effectiveupwelling of more mafic, and hence less viscous, magmas througha propagated vent finally results in the emplacement of thecomposite lava flow. KEY WORDS: high-Mg andesite; sanukitoid; composite lava; solidification; remelting