Studies on the weathering and alteration of minerals by their fine texture analysis

自1978年以来，在Monbuso国际科学研究计划中，我们在巴西地盾的碳酸盐碱性复合体中的不同地点采集了许多岩石和矿物样品。本项目的主要课题是用光学和电子显微镜、EPNIA和/或X射线衍射对矿物的风化和蚀变进行调查。主要结果如下，并分析了风化蚀变的一般特征。（1）在米纳斯吉拉斯的塔皮拉，具有特殊形态的锐钛矿晶体与磷酸盐一起被开采，用作肥料。本文通过对同一矿中的钙钛矿和钙钛矿的精细结构和化学成分的研究，认为钙钛矿是钙钛矿的风化蚀变产物，其特殊形貌可以解释为钙钛矿的假像。（2）碳酸盐岩中含钛磁铁矿的赋存状态和浸出特征 ...更多信息 为了帮助碳酸盐岩成因的研究，对碲-碱络合物进行了研究。研究结果表明，无论磁铁矿的侵入时代如何，也无论其在巴西的位置如何，磁铁矿都经常溶出硅镁矾（MgTiO_3）。(3)On本文通过对碳酸岩中一个云母石英异常分带的研究，认为它与碳酸盐岩浆作用引起的“碱交代”作用密切相关。（4）在钙镁矾中发现钙镁矾、钙钛矾和锆英石，它们都属于Ca-Zr-Ti-O系统。（5）电子显微镜下研究了硅镁矾与碳酸盐岩浆接触交代作用产生的微细结构。（6）用放射性活化分析法对碳酸盐岩红土风化土进行了化学研究。(7)We报告来自巴西五个地区的碳酸岩标本的地球化学和同位素数据。这些分析表明，碳酸盐岩熔体归因于其成因的软流圈地幔柱。少

In the Monbusho International Scientific Research Program since 1978 we sampled many rocks and minerals at various localities in the carbonatitealkaline complexes %, ; hich dot Brazilian shield. Main subjects of the present project are the surveys of weathering and alteration of the minerals with optical and electron microscopy, EPNIA and/or X-ray diffraction. The principal results are summarized as follows, in addition to the analysis of the general features of weathering and alteration.(1)Anatase crystals with a peculiar morphology have been mined together with phosphates for fertilizer in Tapira, Minas Gerais. The present studies on the fine texture and chemical composition of this anatase and perovskite obtained from the same mine, indicate that the anatase should be a weathering and alteration product of perovskite, and its peculiar morphology could be explained as a pseudomorph of perovskite.(2)The occurrence and exsolxition textxire of Ti-bearing magnetite collected in carbonati … More te-alkaline complexes have been investigated in order to help otir study on the origin of carbonatite. The present investigation has demonstrated that the magnetite often exsolves geikielite(MgTiO_3), irrespective of its age of intrusion or locality in Brazil.(3)On the investigation into a mica ivith unusual zoning, which obtained from carbonatites, we have reached the conclusion that it is closely related to the "alkaline metasomatism" caused by action of carbonate magma.(4)The occurrence of polymignyte, zirkelite and zirconolite in glimmerite, all of which belong to the Ca-Zr-Ti-O system, has been described.(5)Fine texture which arises from the contact metasomatism between jacupirangite and carbonate magma has been electronmicroscopically studied.(6)Lateritic weathering soils from carbonate rocks have been chemically investigated with radio activation analysis.(7)We report geochemical and isotopic data of carbonatite specimens from five Brazilian localities. These analyses indicate that carbonatite melts attribute their origin to asthenospheric mantle plume. Less