新疆西昆仑塔什库尔干地区老并铁矿赋矿地层形成时代及其地质意义

Formation Age of Ore-bearing Strata from the Laobing Iron Deposit in Taxkorgan area of Western Kunlun,Xinjiang and Its Geological Significance

马尔洋组是西昆仑塔什库尔干地区铁矿床的赋矿地层,在其中已经发现了赞坎、老并、莫喀尔和叶里克等大型磁铁矿床。由于马尔洋组的形成年代及其归属一直存在是古元古代布伦阔勒群或早古生代的争议,进而影响到矿床的形成年代的厘定。通过对塔什库尔干陆块内老并铁矿区及其外围地区马尔洋组分布及变质变形特征及含矿地层年代学研究,确定了赋矿地层的形成时代,进而对矿床的形成时代进行探讨。研究表明,该套地层无论变质变形特征、含矿特征与布伦阔勒岩群均有着明显不同,且老并矿区内磁铁矿体上盘的长英质片岩和夹层中的黑云石英片岩样品的锆石年龄显示,长英质片岩中继承性碎屑锆石年龄加权平均值为(532±3.9)Ma,黑云石英片岩中继承性碎屑锆石年龄加权平均值为(526±5)Ma,这一年龄对应了马尔洋组源区岩石的年龄,初步认为马尔洋组的形成时代不会早于510 Ma,为早古生代,这些充分证明马尔洋组应该从布伦阔勒岩群解体,由于老并磁铁矿床的形成主要与沉积成矿作用密切相关,其主要矿体是与马尔洋组同生的,因此铁矿床的形成时代应与马尔洋组含铁岩系的形成时代一致,这将进一步明确该地区的磁铁矿床的找矿方向,并提供理论基础。

The Maeryang formation is important ore-bearing strata of the iron deposits in Taxkorgan area of western Kunlun.Many large-sized iron deposits were found within this formation,such as Laobing,Zankan,Mokaer and Yelike iron deposits.Due to the Bulunkuole Group was formed in Proterozoic or early Paleozoic has always been controversial,the formation age and attribution of Maeryang formation are not quite clear,which affect the determination of the forma-tion age of this iron deposits.In this paper,the distribution,metamorphic and deformation characteristics of Maeryang formation have been discussed,and its ore-forming age has been dated and confirmed.The study shows that the Maeryang formation is different from the Bulunkuole Group in the aspects of metamorphic,deformation and ore-bearing characteristics.The results suggest that the average age of felsic schist from Maeryang formation in Laobing iron deposit is（532±3.9）Ma,while the ones of biotite-quartz schist is（526±5）Ma.Thus,it＇s believed that the formation of Maeryang formation was later than 510 Ma,and this formation was separated from the Bulunkuole Group.The formation of the Laobing iron deposit is closely related to sedimentary mineralization,and the main ore-bodies are co-existed with Maeryang formation.Its oreforming age keeps pace with the age of ferruginous strata in Maeryang formation,which provides the prospecting direction and theoretical basis for discovering magnetite deposits in this area.