河南舞阳地区赵案庄铁矿床地质特征、成矿时代及成因探讨

发布时间：2019-04-25 22:38

【摘要】：河南舞阳地区位于华北板块南缘，该区是河南省主要铁矿产地，查明铁矿资源储量占全省总查明资源储量的46%，矿区内铁矿床有两种类型：即产在古元古代铁山庙组的BIF型铁山庙式铁矿床和赋存在新太古代赵案庄组中，与超基性岩体有关的赵案庄式晚期岩浆矿床。与成矿有关的超基性侵入体呈巨大的似层状、透镜状侵入赵案庄组透辉角闪斜长片麻岩中，主要岩石类型为橄榄岩类、辉石岩类和角闪石岩类。赵案庄铁矿床为产于超基性岩中缓倾斜的隐伏矿床，主要产在下部橄榄岩体中。矿体形体与超基性岩体基本一致，矿体厚度与岩体厚度多呈正消长关系。矿体的微观特征显示矿石具有典型的海绵陨铁结构，，橄榄石多已经由于岩浆作用后期自变质作用发生蛇纹石化。以上特征均说明该矿床类型属于晚期岩浆矿床。赵案庄铁矿床矿石成分主要为磁铁矿，与磁铁矿共生的矿物除蛇纹石外，含有大量磷灰石和少量钛铁矿以及金红石和锆石。电子探针数据显示矿石中磁铁矿成分与河北大庙等地区磁铁矿有较大差异，为较“纯净”的磁铁矿，除FeOT外，其他氧化物含量基本小于1%。超基性岩体的演化除早期呈似层状侵入赵案庄组的片麻岩外，在演化晚期还见透辉石岩呈脉状穿切铁山庙组的BIF型矿体和大理岩。赵案庄铁矿体和穿切BIF型矿体的透辉石岩的微量元素分析结果，显示他们可能为同源岩浆演化的产物。微量元素显示他们具有P、Ti等元素的负相关性，这种元素分配特征可以通过宏观上副矿物含量来解释。矿体中含有大量磷灰石和磁铁矿，所以矿体的化学分析结果显示P、Ti等元素含量正异常。而透辉石岩为岩浆分异晚期产物，岩浆演化早期分异出大量磷灰石和钛铁矿，因而岩浆晚期的透辉石岩P、Ti含量较低。在蛇纹磁铁矿石中获取锆石颗粒，进行LA-MC-ICP-MS年龄测定。通过对锆石CL图像分析，说明锆石遭受后期变质作用改造。获得不一致线的上交点年龄为1943±5Ma，是遭受强烈变质作用年龄，也就是矿体形成时代上限。赋矿侵入岩体晚期分异的透辉石岩脉穿切了铁山庙组BIF型铁矿。铁山庙组地层形成在古元古代，其形成时代可以作为矿体形成时代的下限。因而矿体形成于1943Ma 2500Ma，即古元古代。探讨了矿床的成矿物质来源、成矿动力学、成矿特征、结合成矿时代等因素提出矿床成矿模式，认为赵案庄铁矿床是产于超基性岩中的古元古代晚期岩浆分结矿床，是我国目前已知的最古老的岩浆型铁矿床。
[Abstract]:The Wuyang area in Henan Province is located in the southern margin of the North China Plate, which is the main iron ore producing area in Henan Province, and the identified iron ore resource reserves account for 46% of the total identified resources reserves in the province. There are two types of iron deposits in the ore area: the BIF type Tieshanmiao type iron deposit occurred in the Gu Yuan ancient Tieshanmiao formation and the late Zhaozhuang magmatic deposit in the Neoarchean Zhaojazhuang formation, which is related to the ultrabasic rock mass. The ultrabasic intrusions related to mineralization are in a large layer-like form, and lenticular intrusions into the diopside amphibolite gneiss of the Zhaozhuangzhuang formation. The main rock types are peridotite, pyroxenite and amphibolite. Zhaojizhuang iron deposit is a steeply inclined concealed deposit occurring in ultrabasic rocks, mainly in the lower olivine body. The shape of the orebody is basically consistent with the ultrabasic rock mass, and the thickness of the orebody and the thickness of the rock mass are mostly positive fluctuating relationship. The microscopic characteristics of the ore bodies show that the ore has a typical spongy meteorite structure, and the peridotite has been turned into serpentinization due to the self-metamorphism in the late stage of magmatism. All the above characteristics indicate that this type of deposit belongs to the late magmatic deposit. The ore composition of Zhaozhazhuang iron deposit is mainly magnetite. The minerals associated with magnetite contain a lot of apatite and a small amount of ilmenite and rutile and zircon in addition to serpentine. The EPMA data show that the composition of magnetite in the ore is quite different from that in Damiao area of Hebei Province. The magnetite is relatively "pure" magnetite. Except for FeOT, the contents of other oxides are less than 1%. In addition to the gneisses that invaded the Zhaojazhuang formation in the early stage of the ultrabasic rock evolution, diopside rocks were also seen as vein-like BIF-type orebodies and marble in the Tieshanmiao formation in the late stage of evolution. The trace element analysis results of diopside rocks of Zhaozhazhuang iron orebody and through-cut BIF type orebody indicate that they may be the product of the evolution of homologous magma. Trace elements show a negative correlation with P, Ti and other elements, which can be explained by the macroscopical content of accessory minerals. There are lots of apatite and magnetite in the ore body, so the chemical analysis of the ore body shows that the contents of P, Ti and other elements are abnormal. The diopside is a late product of magmatic differentiation, and a large number of apatite and ilmenite were differentiated in the early stage of magmatic evolution, so the P and Ti contents of the diopside in the late magmatic stage are relatively low. Zircon particles were obtained from serpentine magnetite for LA-MC-ICP-MS dating. Through the analysis of CL images of zircon, it is shown that zircon suffered from metamorphism in late stage. The upper intersection age of the inconsistency line is 1943 卤5 Ma, which is the age of strong metamorphism, that is, the upper age limit of ore body formation. Diopside veins of late ore-bearing intrusive rocks cut through BIF-type iron ore deposit of Tieshanmiao formation. Tieshanmiao formation was formed in ancient Gu Yuan, and its forming age can be regarded as the lower limit of ore body forming age. As a result, the orebody was formed in 1943Ma, 2500 Ma, that is, the ancient Gu Yuan. The ore-forming model of Zhaozhazhuang iron deposit is put forward according to the ore-forming age and other factors. It is considered that the Zhaozhazhuang iron deposit is a late-stage magmatic ore-splitting deposit of Gu Yuan, which occurred in ultrabasic rocks, and the ore-forming characteristics of the deposit are discussed in this paper. It is the oldest magmatic iron deposit known in China.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P618.31

【参考文献】