阿尔金喀腊大湾铁矿田褶皱构造特征及找矿意义  

Characteristics of Folds in the Kaladawan Iron Orefield, Altun Mountains, Northwestern China and its Prospecting Implication

作　　者：陈柏林[1] 孟令通[1] CHEN Bailin;MENG Lingtong(Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081,China)

机构地区：[1]中国地质科学院地质力学研究所,北京100081

出　　处：《大地构造与成矿学》2018年第1期32-49,共18页Geotectonica et Metallogenia

基　　金："十二五";"十一五"国家科技支撑计划重点项目(2011BAB06B08-04;2006BAB07B02-04);地质矿产调查专项(1212011085043)共同资助

摘　　要：通过对阿尔金山喀腊大湾铁矿田内构造的系统研究,确认矿田中东段为单斜层构造,南侧为较老的下部岩层,北侧为较新的上部岩层,岩层总体倾向北,在7910铁矿床局部出现倒转倾向南。铁矿田西段为陡枢纽褶皱构造,含铁层位(卓阿布拉克组第三岩性段第一岩性层,即下部玄武岩层)与其上覆的第二岩性层(大理岩层,标志层)、第三岩性层(上部玄武岩层)以及第四岩性段沉积岩系自7914铁矿床向西逐渐转向呈半圆形状弯曲(由EW向逐渐转向至SW向?NS向?SE向?SEE向)延伸,转折端及附近发育低级别"M"型及"S"型和"Z"型褶皱,构成直立陡倾伏背斜构造,轴面近直立东西走向,枢纽约71?向西陡倾。卓阿布拉克第四岩性段组成的外层也呈现同样的褶皱构造形态。褶皱南翼大部被后期中酸性侵入岩侵位吞噬,仅残留八八铁矿床一带一小部分,形成铁矿带和含矿层位呈横卧"L"状形态;该陡枢纽褶皱形成时间介于517~482 Ma之间。铁矿田东段7910铁矿床深部的铁矿体呈向形构造,不是较大规模的褶皱,而是规模有限的局部次级褶皱构造,在自东向西观察的剖面中其形态特征为"Z"形(因为岩层产状近直立,更像"N"形)。该次级褶皱的形成与剖面上南侧较老下部岩层的相对上升、北侧较新上部岩层的相对下降的层间相对运动以及铁矿南侧花岗质杂岩体侵位和隆升有关。铁矿床和铁矿层均受火山岩特定岩性和层位以及褶皱构造控制,依据次级褶皱的形态,含铁层位将继续向深部延伸,所以深部存在很大的铁矿找矿潜力。The Kaladawan iron orefield in the Alun Mountains is located in the area sandwitched between the NE striking Altun strike-slip faults and EW striking northern Altun fault.A comprisensive investigation on the structures of Kaladawan iron orefield demonstrated that(1)there is a monocline in the eastern part of the orefield where the strata dip to north in general,while locally reversed in areas such as the7910iron deposit;(2)a steeply hinge fold in the western part of the orefield consists of the iron-bearing rocks(the first part of third sub-formation of the Zhuo’abulake Formation)and the overlying second to the forth sub-formation of the Zhuo’abulake Formation,and its formation age is constrained to be517?482Ma by the ages of the volcanic-sedimentary rock and the medium-acid intrusive rock;(3)the major part of the south limb of the fold is trucated by the medium-acid intrusion;(4)a synformal fold at the7910iron deposit in the eastern part of the orefield is a subordinary fold(100?200m);(5)the formation of the subodinary synformal fold is likely related the interlayer movement and uplift due to the emplacement of the medium-acid intrusion;(6)the iron ore-bodies are controlled by the volcanic sedimentary rocks and fold structures.Analyses of the second-order synformal fold,iron-bearing strata of the orefield show that there is a great potential for iron prospecting at the depth.

关 键 词：陡枢纽褶皱 向形构造 次级褶皱 找矿潜力 喀腊大湾铁矿田 阿尔金山 

分 类 号：P542[天文地球—构造地质学]