西昆仑新元古代大红柳滩BIF铁矿成矿物质来源和成矿环境研究

The Dahongliutan hematite-rich Fe deposit, in Western Kunlun orogenic belt, is the youngest banded iron formation in China. This Fe deposit was formed at ca. 532 -593 Ma. Previous research on this deposit is very poor due to geographic remoteness and bad road access. Combined with the previous study including geological characteristics, ore-forming age and metallogenic geodynamic setting, we will carefully divide the mineralization stages. After the major element, trace element, rare earth element (REE+Y), Nd and Fe isotope measurements of wall rocks and Fe ores, as well as C-O isotopes analyses on carbonate minerals and O isotope analysis of hematite, we attempt to trace ore-forming material source and depositional setting. According to above research, this project is aimed at discussing genesis relationship for Fe ores of different types, metallogenic process and metallogenic mechanism, based on the comparison with typical/smilar BIF deposits in the world, and further analyzing genesis of the deposit and establishing metallogenic model. Moreover, The project not only will guide the next prospecting in Western Kunlun area, also provide a scientific basis for Neoproterozoic banded iron formation system.

西昆仑大红柳滩赤铁矿是我国目前发现时代 (532 ~ 593 Ma) 最新的BIF型矿床，研究工作十分薄弱。本项目拟结合申请者前期从事的矿床基础地质特征、年代学和成矿动力学背景研究，划分成矿期次和成矿阶段，系统开展围岩和不同类型矿石的主量元素、微量元素、稀土元素 (REE+Y)、Nd同位素、Fe同位素、碳酸盐矿物C-O同位素和赤铁矿O同位素分析，示踪成矿物质来源和成矿环境，阐述不同类型矿石的发育机制和成因联系，揭示成矿过程和成矿机制，对比国内外典型/类似BIF矿床成矿特征，确定矿床成因类型，建立成矿模式，以期指导西昆仑铁矿的进一步找矿方向，为推进新元古代BIF成矿体系研究提供科学的理论依据。

西昆仑大红柳滩赤铁矿是我国目前发现时代 (532 ~ 593 Ma) 最新的BIF型矿床，研究工作十分薄弱。本项目综合矿床地质特征、年代学、矿物学、元素地球化学和Nd-Fe-C-O同位素地球化学探讨成矿动力学背景，厘清成矿期次及成矿阶段，示踪成矿物质来源和成矿环境，揭示成矿过程和成矿机制，建立成矿模式。通过系统研究，取得了如下重要成果：（1）提出大红柳滩BIF的成矿动力学背景与超大陆（Rodinia和Gondwana）和原特提洋演化密切相关；（2）识别出3种主要类型BIF，为氧化物相、硅酸盐-碳酸盐-氧化物相、碳酸盐相（包括铁白云石和菱铁矿亚相），划分出沉积-成岩期、变质变形期和表生氧化期3个成矿期次；（3）创新性的提出大红柳滩BIF成矿物质（Fe和Si）具多源性，源自海底高-低温热液（Eu/Eu ∗ PAAS = 1.10 ~ 5.23）、周围海水和DIR进程还原的古老大陆地壳风化产物（εNd(t)= −13.52~ −19.60；δ56Fe= −0.10 ~ −0.21‰）的混合，同时成矿过程中混入了不同比例的陆源碎屑物质；（4）揭示了大红柳滩BIF沉积环境为上部氧化和下部缺氧富Fe2+的分层海水（菱铁矿和铁白云石δ13CV-PDB= −4.0‰ ~ −6.6‰；白云石和方解石δ13CV-PDB= −0.8‰ ~ +3.1‰）；（5）厘清了成矿过程和矿石矿物形成机理，建立了全新的成矿模式；（6）丰富和完善了新元古代BIF的成矿理论。