钛的地球化学性质与成矿

Geochemistry and mineralization of titanium

钛由于其高强度和抗腐蚀性特征,在航空航天、医药、手机等领域得到越来越广泛的应用,是二十世纪的战略金属元素。在自然界中,钛铁矿、钛磁铁矿和金红石是最具经济价值的含钛矿物。钛最初被认为是变质过程中最不活泼的金属元素之一,随着越来越多的证据显示钛可以在特定条件下进入变质热液流体中发生活动迁移。高压变质脉体中金红石和磷灰石作为共生矿物存在,这可能为富F溶液对钛迁移富集的影响,当氟磷灰石从富F流体中结晶沉淀时K2TiF6络合物分解,钛在其中的溶解度降低进而结晶沉淀出金红石,而这一富集迁移沉淀机制很可能是变质型金红石矿床变质富集的机制。在岩浆矿床中,钛常作为伴生元素赋存于磁铁矿床中。一般认为部分熔融程度、挥发分含量和成矿岩浆温度等决定了含钛矿或高钛岩体的形成,本文认为富金红石的再循环洋壳或者富钛沉积矿床重熔是岩浆型钛矿床的重要成矿物质来源。沉积型钛矿床的形成与区域地质、地理和水动力学有关,它们常在被动大陆边缘,以高风化、高品位钛源岩为后盾通过风化、剥蚀和海侵等主要形成在沿海岸带特别是南北纬30°低纬度地区。总之富钛源区、起源深度、部分熔融温度和程度、陆壳混染程度、挥发分、流体成分、风化剥蚀能力等决定了钛矿化成功与否。

Titanium,because of its high strength and corrosion resistance,has been widely used in aerospace,medicine,mobile phone and other fields.It is a strategic metallic element in the 20^th century.In nature,ilmenite,titanomagnetite and rutile are the most economical titaniferous minerals.Titanium was initially considered to be an inactive metallic element,however,more and more evidences support that it can migrate into metamorphic hydrothermal fluids in certain conditions.The presence of rutile and apatite as paragenetic minerals in high-pressure metamorphic veins may be due to the influence of F-rich fluids on the migration and enrichment of Ti.When fluorapatite precipitates from the F-rich fluids,the K 2 TiF 6 complex will decompose,therefor the solubility of Ti will decrease and rutile will crystallize,which is probably the mechanism of metamorphism and enrichment of the metamorphic rutile deposit.In the magmatic deposits,titanium is often associated with magnetite deposits.It is generally believed that the degree of partial melting,volatile content and the temperature of ore-forming magma determine the formation Ti-bearing deposits or high Ti intrusions.This paper considers that the remelting of recycling rutile-rich oceanic crust or Ti-rich sedimentary deposits is the important source of ore-forming materials for magmatic-type titanium deposits.The formation of sedimentary titanium deposits are related to regional geology,physiography and hydrodynamics.They are often located on the passive continental margin,with high weathering,high-grade titanium sources through weathering,denudation and transgression,and are mainly formed along the costal zone,especially between the low latitudes of 30°N and 30°S.In conclusion,the successful mineralization of Ti is determined by the Ti-rich sources,the depth of provenance,the temperature and degree of partial melting,the degree of contamination of the continental crust,volatile content,the ability of weathering and denudation,etc.