华南东部中新生代火山岩型铀矿成矿规律,勘查模式及找矿远景

中新生代时期，华南东部地壳经历了挤压－松驰拉张－局部裂解的演化过程。相应地发育３期火山活动，构成初火山族回、主火山旋回和破火山旋回。破火山使回出现双峰式岩套，标志着已进入胚胎型裂谷演化阶段。火山岩型铀矿具有破火山族回成矿、破火山旋回活动带控矿、二次迭加富集特性，可称其为破火山系列新不整合脉型铀矿。划分为体型、层型和脉型３种形态类型和相应的勘查模式。华南东部破火山系列新不整合脉型铀矿具有巨大的找矿潜力，在花岗岩基底上发育的破火山旋回构造－岩浆杂岩区，是今后寻找大型铀矿的有利靶区。     

山东五莲七宝山破火山口的研究

本文首次研究了七宝山破火山口,对破火山口特征作了全面论述,尤其是发现破火山口产有两套火山——侵入杂岩,粗安质火山侵入杂岩和英安流纹质火山侵入杂岩,前者为慢源岩浆经破火山口中心式喷发形成,后者为陆壳同熔岩浆在破火山口演化晚期经火山复活作用产生。     

570矿床控制因素及富矿形成条件

570矿床地质背景是破火山旋回边缘活动带;矿床定位要素是受破火山断裂系统构造结控制的隐爆角砾岩筒;隐爆加断陷组成的聚矿结构,是富矿形成的主要条件;隐爆角砾岩筒与次火山花岗岩浆侵位组成的热泵汲取效应,是矿床基本成因模式。矿床扩大方向是在探索隐爆角砾岩筒深部的同时,沿边缘活动带,在破火山断裂系统构造结处寻找新的隐爆角砾岩筒。     

江西东乡赛阳关破火山口的特征及演化

赛阳关破火山口火山活动具多期次性,以多相火山一次火山侵入相为特点。火山喷发物成份的规律变化,表明岩浆源呈层状垂直分带。破火山口的塌陷具不均一性,明显偏向东南一侧,其演化过程为:中心式熔岩溢流,揭开火山活动的序幕;沿环状裂隙强烈的火山灰流喷发,进入破火山口发育阶段;以及由此而产生的沉陷。     

浙江省庆元破火山地球物理地球化学特征及地质意义

庆元破火山以中心式仙桃山岩体为中心,高、中、低温成矿元素异常依次由内向外分布。它们各自拥有不同的空间展布,矿物组成,结构构造,围岩蚀变和伴生元素特征。通过地球物理与地球化学有机结合,深入探讨破火山的空间分布特征,可以开拓寻找不同类型的矿产资源及矿产资源远景评价的思路。     

九华山复式杂岩体的构成及主要特征

九华山复式杂岩体由东堡岩体、上菥荻岩体和天台岩体三部分构成。它们之间呈不同形式的侵入接触。各岩体的空间分布、岩浆演化及内部构造等特征均显示它们的独立性。在岩石学、地球化学等方面三者均有明显区别，定位机制也各具特色，东堡岩体以顶蚀作用为主，上菥荻岩体为破火山口沉陷式，天白岩体则为岩墙扩张式定位。     

Mineralized and unmineralized calderas in Spain; Part II, evolution of the Rodalquilar caldera complex and associated gold-alunite deposits

The Rodalquilar caldera complex is located in the western part of the Cabo de Gata volcanic field in southeastern Spain and is the first documented example of epithermal gold-alunite mineralization within a caldera in Europe. The Rodalquilar caldera is an oval collapse structure having a maximum diameter of 8 km and formed at 11 Ma from eruption of the Cinto ash-flow tuff. The oval Lomilla caldera, with a diameter of 2 km, is nested within the central resurgent dome of the older Rodalquilar caldera. The Lomilla caldera resulted from the eruption of the Lazaras ash-flow tuff which was ponded within the moat of the Rodalquilar caldera. The last phase of volcanic activity in the caldera complex was the emplacement of hornblende andesite flows and intrusions. This magmatic event resulted in structural doming of the caldera, opening of fractures and faults, and provided the heat source for the large hydrothermal systems which deposited quartz-alunite type gold deposits and base metal vein systems. The gold-alunite deposits are enclosed in areas of intense acid sulfate alteration and localized in ring and radial faults and fractures present in the east wall of the Lomilla caldera. Like other acid-sulfate type deposits, the Rodalquilar gold-alunite deposits are closely related in time and space to porphyritic, intermediate composition magma emplaced along caldera structures but unrelated to the caldera forming magmatic system.     

A Proposal of Caldera-Related Genesis for the Roseki Deposits in the Mitsuishi Mining Area, Southwest Japan

Abstract: Geology of the largest Roseki (pyrophyllite–clay)–mineralized, Mitsuishi mining area was re–examined, and a composite caldera model (Wake caldera) was proposed. Evidence for the caldera formation is (1) Existence of huge volume of rhyolitic tuffs in the mining area, (2) A basin structure in rhyolitic tuffs surrounded by the Permo-Triassic basement rocks, (3) Arc-like distribution of the Roseki deposits along the eastern edge of the proposed caldera, (4) Tectonic disturbance and intrusive bodies along the caldera wall, and (5) Presence of meso– and mega-breccias at the bottom of the caldera wall. The proposed caldera, sizing NNW-SSE 23 km by ENE-WSW 15 km, may have younger, Inner caldera (15 by 15 km), defined by Lower Member of the late Cretaceous rhyolitic tuffs, thus composite in character. The Roseki deposits were formed after the Inner caldera collapse by hydrothermal fluids ascended through the caldera wall, then spread into the permeable horizon. This caldera proposal bears a significant change in the regional exploration strategy for the Roseki deposits.     

庐枞火山喷流、潜火山气液叠加改造型铁硫矿床的定位控制

该类型矿床形成过程，主要可划分为火山喷流沉积和潜火山气液叠加改造两大成矿、蚀变期。从破火山口演化规律入手，分析研究了环形火山构造对矿床形成的制约作用。     

Caldera-related volcanic rocks in the Shammar Group, northern Arabian Shield

Volcanic formations of the ca 630-620 Ma old Shammar Group in the Tuluhah area in the northern Arabian Shield occupy an oval area some 8×12 km. They overlie sedimentary rift-fill of the Kuara Formation and are interpreted as related to the formation of a caldera, here named the Awad Caldera. The earliest of the volcanic formations, the Dabsah Tuff, is more than 450 m thick in the south and wedges out in the north. It is composed of silicic, medial to proximal pyroclastic flow rocks that record an eruption during which an initial caldera is interpreted to have formed by probably trapdoor-style collapse. The Nijab Basalt, more than 200 m thick and present as flows overlying the Kuara Formation to the north of the caldera, is presumed to have originated outside the study area during an interval between periods of silicic volcanic activity, and to have flowed onto the Dabsah Tuff in the first-stage caldera. The succeeding Mindassa Megabreccia contains large rafts of the older Shammar rocks, mainly Nijab Basalt, in a tuff matrix, and is regarded as probably a caldera collapse and fallback megabreccia formed during a silicic eruption that led to the second stage of caldera development. The megabreccia is overlain by the post-collapse Sutayih Tuff, more than 450 m thick, composed of proximal pyroclastic flow units.