矿床地质2018，Vol.37Issue(1)：1-26,26.DOI:10.16111/j.0258-7106.2018.01.001
冰川底部富铁溶液氧化沉淀:塔里木北缘新元古界库鲁克赛铁矿床的成因
Oxidation and deposition of iron-rich saline water below glacier cap: Genesis of Neoproterozoic Quruqsay iron deposit on northern margin of Tarim craton
摘要
Abstract
Banded Iron Formations (BIFs) reappeared during the Neoproterozoic,after about 1 billion years of absence in sedimentary records from the last deposition of Superior-type BIFs at 1.8 Ga.This type of iron formation is commonly associated with deposition of Neoproterozoic glacial facies which proceeded with the Cambrian radiation of metazoans,reflecting dramatic environmental change.A detailed understanding of mechanisms of Fe oxidation and accumulation during the Cryogenian period provides insights into evolution of the Earth as a system and biological innovations during this critical geological interval.In this paper the authors studied the hematiterich Quruqsay iron deposit on the north margin of Tarim craton,which is associated with Neoproterozoic glaciation but was rarely reported in previous studies.Based on zircon U-Pb dating and regional stratigraphic correlation,the authors constrained the deposition age of the Quruqsay iron deposit between the early Qingbaikou period and the late Nanhua period in Neoproterozoic.Zircon age spectrum and petrographic features show that the clastic materials associated with hematite deposits were mainly from the Duduanshan Group,which was the upper part of the formation of Qingbaikou system.Major and trace element compositions indicate that hematite from the Quruqsay iron deposit was formed in an oxygen rich environment,and the ore-forming materials were mainly derived from continental crust,with only a small proportion of contribution from hydrothermal fluids or seawater.Geological and geochemical evidence suggests the close affinity between iron and continental glacier in the Quruqsay iron deposit,which is radically different from the Cryogenian Raptian-type BIFs,for which hydrothermal origin of Fe is commonly proposed.The authors argue that the iron source for the Quruqsay deposit originated from saline water below the glacier cap,which liberated Fe2 + from subglacial rocks during the progression of glaciers,and the subglacial Fe2 + fluids were oxidized at the edge of the glacier when it migrated into the ocean.Such mechanism of Fe2+ mobilization and oxidation has been observed from a modern glacier system at the Taylor Glacier in Antarctica,known as the famous "Blood Falls".The authors hold that the Quruqsay iron deposit is an example of the "Blood Falls"-type iron formation,which has a unique iron mineralization model sourced from surficial continental rocks,which is distinct from commonly proposed Archean BIF models and the Raptian BIF models.关键词
地球化学/新元古代/铁建造/冰川作用/库鲁克赛/塔里木Key words
geochemistry/Neoproterozoic/iron formation/glaciation/Quruqsay/Tarim分类
天文与地球科学引用本文复制引用
高丙飞,吴昌志,李伟强,杨涛,叶辉,雷如雄,刘倩..冰川底部富铁溶液氧化沉淀:塔里木北缘新元古界库鲁克赛铁矿床的成因[J].矿床地质,2018,37(1):1-26,26.基金项目
本文得到国家自然科学基金(编号:U1603114)和中国地质调查局工作项目(编号:1212011140056)联合资助 （编号:U1603114）
