摘要
马达加斯加南部Tranomaro地区钍矿石中发现了自然界中极为罕见的钙柱石（Me=87.8%~99.2%）,钙柱石主要产于Anosyan花岗岩体（主要为紫苏花岗岩）与碳酸盐岩接触部位所形成的钙质夕卡岩和大理岩中,与透辉石、石榴石、橄榄石、硅灰石、金云母、钙长石、方解石和角闪石等共生。化学分析显示,除Si O2、Al2O、Ca O和Na2O等主要组分（w（Si O2）=40.95%~43.91%,w（Al2O3）=29.48%~36.10%,w（Ca O）=19.23%~21.86%,w（Na2O）=0.30%~1.60%）外,钙柱石中还含有CO2-3、F-、Cl-和SO3等。钙柱石的合成实验及矿物学研究表明,该地区钙柱石是在温度大于850℃,压力300~500 MPa条件下,且富含CO2和Ca2＋的地质环境中形成。钍矿石中钙柱石的发现表明：方钍石等钍矿物形成的温度超过850℃,形成深度约为9.9~16.5 km;与钍成矿有关的流体是超临界的气-液流体;流体中富含的F和CO2等组分对该地区钍成矿起着决定性的作用。
In Tranomaro, Sourthen Madagascar, meionite（Me=87.8%-99.2%） which is extremely rare in the nature is discovered in thorium ore. Meionite mainly originated in marble and calcareous skarns which formed at the contact point of Anosyan granite body（main component is charnockite） and carbonite is symbiotic with diopside, garnet, olive, wollastonite, phlogopite,anorthite,calcite,amphibole, and etc. The chemical analysis indicates that apart from the main components Si O2（40.95%-43.91%）, Al2O3（29.48%-36.10%）, Ca O（19.23%-21.86%）, Na2O（0.30%-1.60%）, meionite also contains CO2- 3,F,Cl,SO3,and etc. Meionite synthesis experiments and mineralogical studies show that meionite formed in geological environment at temperature ≥850 ℃, under the pressure of about 300-500 MPa and also rich in CO2 and Ca. The discovery of meionite in thorium ore shows that the temperature to form thorianite is higher than 850 ℃ at the depth of about 9.9-16.6 km. The fluid associated with thorium minerogenic is supercritical air-liquid fluid. The liquid which is rich in F and CO2 plays a crucial role for thorium minerogenic in this region.
出处
《矿物学报》
CAS
CSCD
北大核心
2015年第3期406-410,共5页
Acta Mineralogica Sinica
