内蒙古正蓝旗羊蹄子山-磨石山钛矿区两种不同成因类型的锐钛矿富矿体

Two different genetic types of anatase-dominated rich ores in Yangtizishan-Moshishan titanium deposit and their metallogenic characteristics

内蒙古正蓝旗羊蹄子山-磨石山钛矿床有两种不同类型的锐钛矿富矿体,即产于北部磨石山矿带的沉积变质型锐钛矿富矿体和产于南部羊蹄子山矿段的热液改造型锐钛矿富矿体。两类富矿体在矿体规模、形态、矿石结构构造特征、矿石矿物共生组合、矿石化学成分、锐钛矿粒度和成矿时代及成矿机理等方面,都存在较明显的差异。沉积变质型锐钛矿富矿体呈层状、似层状产出,矿石具有明显的细条纹状构造;由以石英为主的条纹和以锐钛矿、金红石、钛铁矿、直闪石(±黑云母、石榴子石)为主的条纹互层组成;矿石品位(TiO2)为5.0%～15.46%,平均值为8.64%,Fe2O3+FeO含量中等(6.99%～15.61%),锐钛矿颗粒细小(0.01～0.1mm);形成于元古宙〔(1751±8)Ma〕二道凹群变质岩系中。热液改造型锐钛矿富矿体呈透镜状,规模相对较小;矿石具有块状、网脉状、细脉浸染状构造;共生矿物除锐钛矿、金红石、钛铁矿、石英外,常有较多的叶片状赤铁矿,局部有直闪石、黑云母和石榴子石;锐钛矿粒度较大(0.05～0.2mm,少数可达0.5mm),且分布不均匀;是在元古宙沉积变质富锐钛矿变质石英砂岩的基础上,经燕山晚期〔(118±3)Ma〕花岗岩侵入,遭受热液改造而成。

Based upon forms of ore bodies, structures, mineral paragenesis of ores, ore composition and granularity anatase, the authors identified two different genetic types of anatase-dominated rich ores in the Yangtizishan titanium deposit, i.e., the metamorphosed sedimentary type occurring in the Moshishan ore belt and the hydrothermal reformation type occurring in the Yangtizishan ore belt. The former anatase-dominated rich ore type was formed in Proterozoic[（1 751 ±8）Ma], and the latter was reformed by hydrothermalism of granite in the Late Yanshanian stage [（ 118 ± 3）Ma]. The metamorphosed sedimentary anatase-dominated rich ore bodies have bedded form and the ores have perthitic structure comprising chiefly interbedded quartz perthite and anatase （rutile ＋ ilmenite, anthophyllite, ± biotite） perthite. Ore grade （TiO2） of these ores are 5.0%- 15.46%, averaging 8.64%, with medium content of Fe2O3 ＋ FeO being 6.99% -15.61%. The sizes of anatase grains are very small （0.01-0.1 mm）. The ore bodies of hydrothermal reformed anatase- dominated rich ores are in the lenticular form. The ores have massive, stockwork or veinlet- disseminated structure with relict perthitic structure. The main associated minerals of ores are anatase, rutile, hematite, ilmenite, and quartz, with locally an- thophillite, biotite and garnet. These ores contain TiO2 from 4.29% to 10.20% with an average of 5.94%, and have more Fe2O3 ＋ FeO contents （ 14.07 % - 38.88 %, locally 62.36 % ）. The sizes of anatase grains in the rich ores （0.05-0.2 mm, with a few as large as 0.5 mm）are larger than those in the former ore type. The distribution of the anatase assemblage of this ore type is uneven.