Abundances of F,Cl S and P in Volcanic Magmas and Their Evolution,Wudalianchi

F, Cl, S and P were determined, using electron microprobe, in magmatic inclusions trapped within minerals and glass mesostasis from Wudalianchi volcanic rocks. The initial volcanic magma from Wudalianchi corresponds to the basanitic magma crystallized near the surface ( pressure < 91 Mpa ). The potential H₂O content of this magma is in the range 2 — 4 wt. %. The initial composition of volcanic magmas varies regularly from early to late volcanic events. From the Middle Pleistocene to the recent eruptions (1719 – 1721 yr.), the basicity of volcanic magma tends to increase, as reflected by an increase in MgO and CaO contents and by a progressive decrease in SiO₂ and K₂O contents. Meanwhile. from early (Q₂ ) to late (Q₃) episodic eruptions of the Middle Pleistocene, the initial concentrations of chlorine in volcanic magmas range from 1430 – 1930 ppm to 1700 ppm and decrease to 700 — 970 ppm for the first episodic eruption during the Holocene (Q ₄ ¹ ). The chlorine concentrations of volcanic magmas of recent eruption (Q ₄ ² ) are increased again to 2600 – 2870 ppm. A parallel evolution trend for phosphorus and chlorine concentrations in magmas has been certified: 1500 – 5970 ppm (Q₂)→ 3500 – 4210 ppm (Q₃)→ 1100– 3500 ppm (Q ₄ ¹ )→ 6800– 7900 ppm (Q ₄ ² ). The fluorine contents of volcanic magmas, from early to late volcanic events, show the same trend: 770 – 2470 ppm → 200–700 ppm → 700 – 800 ppm. During the crystallization-evolution of volcanic magmas, fluorine and phosphorus tend to be enriched in residual magmas as a result of crystal-melt differentiation. for example. the fluorine contents reach 5000– 6800 ppm and the phosphorus contents, 2.93wt.% in residual magmas. An appreciable amount of chlorine may be lost from water rich volcanic magmas prior to eruption as a result of degassing. Apparently, water serves as a gas carrier for the chlorine. The chlorine contents of residual magmas may decrease to 100 – 300 ppm. The volcanic magmas from Wudalianchi are poor in sulfur, normally ranging from 200 to 400ppm. On account of the behavior of sulfur in magmas and the strontium and oxygen isotopic analyses ((⁸⁷Sr /⁸⁶Sr)_i=0.70503– 0.70589; δ¹⁸O = + 5.50 – + 6.89 ‰ ), it can be considered that the basanitic magmas in the Wudalianchi volcanic area came from the upper mantle and have not yet been contaminated probably by continental crust materials.     

An Experimental Study on Picromerite Equilkibrium in the Five—Component Brine System K—Na—Mg—Cl—SO4—H2O

This paper presents the results of experiments on the physicochemical conditions for the formation of picaromerite in the five-component brine system K-Na-Mg-Cl-SO4-H2O and the process of isothermal evaporation-crystallization of picromerite from brines.The metastable phase fields of picromerite at 15,10 and 5℃and its stable equilibrium phase field at -5℃ have been established.In addition,the phase equilibrium relationships have also been established for other salt minerals.The lower limit of formation temperature of picromerite has been deduced on the basis of experi-mental results.The isothermal evaporation crystallization path of the invariant assemblage(point D) of picromerite,epsomite,sylvite and halite at 25,15,10 and 5℃ has been revealed.Furthermore,some controversial problems are approached concerning the 25℃“solar” diagram and the 25℃ metastable phase diagram of this system.     

Mantle Ichor HACONS—Its Geological Significance（Ⅱ）

The chemistry and migration patterns of the mantle ichor are discussed on a globle scale followed by evaluations of the significance of HACONSfluid with respect to various geological processes of fundamental interest.     

大田前峰硫多金属矿成因探讨

大田前峰硫、多金属矿的成矿地质条件在闽西南区多金属矿中具有广泛的代表性. 本人通过对矿石中某些矿物的标型特征和矿石结构构造进行研究.发现该区主要矿石矿物之一的磁黄铁矿具有三种同质多相变型:单斜相、斜方相、六方相。矿物相转变反映了成矿物理化学条件的改变。由特征矿物组合的演化过程入手并结合地质特征,初步认为该区硫、多金属矿主要是沉积变质、热液改造叠加型的层控矿床。     

福建银场硫多金属矿床中的银

<正> 硫多金属矿床是福建省硫的主要来源,随着地质工作的深入,部分硫多金属矿床(尤其是硫铅锌矿床)已成为索取银矿的主要对象。一、地质概况银场硫多金属矿床位于闽西南坳陷之大田龙岩次级坳陷中段东缘,政和-大埔断裂带与次级东西向张地大尤北断裂的交汇处。区内呈单斜构造,断裂发育(图1)。出露     

广东阳春黑石岗硫铁矿床溶洞矿中镉的地球化学及硫镉矿的成因意义

<正> 一、矿区地质简况阳春黑石岗硫铁矿区位于广东湛江地区,硫铁矿床中溶洞矿矿体赋存于黑石岗背斜两侧。背斜轴部为燕山期花岗闪长岩,翼部为下石炭统石磴子段大理岩、结晶灰岩。矿体产于接触带。主矿体(Ⅱ号)呈似层状产于背斜的北西侧。矿床中银、铅、锌的硫化物溶洞矿矿体多受原生硫铁矿体或后期构造的控制。溶洞矿在空间上多与黄铁矿体或含银铅     

湖南省黄铁矿床地质地球化学特征初步探讨

湖南省黄铁矿资源颇为丰富,已探明工业矿床50多处。矿床成因类型,可划分为岩浆热液型、层控型和沉积型3类6个亚类,以前两类最重要。岩浆热液型黄铁矿床,主要分布在湘东和湘南地区,与燕山期酸性小岩体密切有关,矿体形态复杂,矿石品位较富,矿物成分繁多,围岩蚀变发育,矿床规模较大;黄铁矿中Co/Ni>1、S/Se比值较低,矿石硫同位素组成具塔式分布效应,矿床硫源以岩浆硫为主,亦有部分地层沉积硫。层控型黄铁矿床,集中分布在湘西北和湘中地区,矿床的产出与岩浆岩无成因联系,受上震旦统陡山沱组和中泥盆统棋梓桥组等特定层位、岩相和岩性组合严格控制,矿体多呈似层状、透镜状等整合矿体,矿石品位一般较贫,矿物成分与围岩蚀变简单:黄铁矿中Co/Ni<1,S/Se比值较高,矿石δS~(34)‰离差大,在较大正、负值范围具多峰式分布,均一化程度低;矿床硫源,为古海水硫酸盐硫和生物成因硫等的混合硫。