CAJ | 학술논문

内蒙古中部发育一条近东西向的含铜镍铂镁铁超镁铁质岩带,宽30 km,长约400 km。该含铜镍铂镁铁超镁铁质岩带位于华北板块北缘深大断裂两侧,横跨两个构造单元：宝音图岩浆弧和狼山白云鄂博台缘坳陷。研究区所处地理位置相对偏僻,研究程度较浅,近年来发现的多处铜镍矿床(点)均分布在该岩带内,逐渐引起地质学者的关注。本文主要通过分析、总结各含矿岩体地球化学数据,对该含铜镍铂镁铁-超镁铁质岩带开展岩石地球化学特征研究。区内岩体形成时代主要集中在314~269 Ma,应属华力西晚期产物。主量元素化学组成表明,该含铜镍铂镁铁-超镁铁质岩主要为拉斑玄武岩系列,部分为钙碱性系列。辉长岩、辉石岩稀土配分模式分两类：轻、重稀土分馏不明显的相对平坦型和轻稀土相对富集、重稀土比较平坦的右倾型(LaN/YbN 为1.49~20.08),Eu 为正异常或负异常(δEu 为0.56~1.66)；辉橄岩稀土元素配分呈轻稀土相对富集、重稀土比较平坦的右倾型(LaN/YbN 为5.56~13.57),Eu 为负异常(δEu 为0.57~0.83)。岩石稀土配分模式总体表现出轻稀土相对富集,重稀土相对平坦的右倾型,稀土总量由辉长岩→辉橄岩呈规律的降低。各类岩石微量元素也各具特色,总体表现出亏损高场强元素 Nb、Ta、Zr。岩浆在演化过程中发生了一定程度的同化混染作用。此外,各岩体表现出高 MgO、低碱的特征,具有较高的Mg#、m/f 比值,显示较好的含矿潜力。
내몽고중부발육일조근동서향적함동얼박미철초미철질암대,관30 km,장약400 km。해함동얼박미철초미철질암대위우화북판괴북연심대단렬량측,횡과량개구조단원：보음도암장호화랑산백운악박태연요함。연구구소처지리위치상대편벽,연구정도교천,근년래발현적다처동얼광상(점)균분포재해암대내,축점인기지질학자적관주。본문주요통과분석、총결각함광암체지구화학수거,대해함동얼박미철-초미철질암대개전암석지구화학특정연구。구내암체형성시대주요집중재314~269 Ma,응속화력서만기산물。주량원소화학조성표명,해함동얼박미철-초미철질암주요위랍반현무암계렬,부분위개감성계렬。휘장암、휘석암희토배분모식분량류：경、중희토분류불명현적상대평탄형화경희토상대부집、중희토비교평탄적우경형(LaN/YbN 위1.49~20.08),Eu 위정이상혹부이상(δEu 위0.56~1.66)；휘감암희토원소배분정경희토상대부집、중희토비교평탄적우경형(LaN/YbN 위5.56~13.57),Eu 위부이상(δEu 위0.57~0.83)。암석희토배분모식총체표현출경희토상대부집,중희토상대평탄적우경형,희토총량유휘장암→휘감암정규률적강저。각류암석미량원소야각구특색,총체표현출우손고장강원소 Nb、Ta、Zr。암장재연화과정중발생료일정정도적동화혼염작용。차외,각암체표현출고 MgO、저감적특정,구유교고적Mg#、m/f 비치,현시교호적함광잠력。
A Cu-Ni (PGE)ore-bearing mafic-ultramafic rocks belt is exposed in central Inner Mongolia,EW extending about 400km long and 30km wide.This belt is located on both sides of the fracture of the North China Craton and stretches across two tectonic units:Baoyintu magmat-ic arc and Bayan Obo marginal rift.As a remote geographical position,the research is relativelyweak in this area.In recent years,many Cu-Ni (PGE)deposits (ore occurrences)including Ebu-tu,Dabuxun,Tepogeritu,Wengeng,Kebu,Huanghuatan and Xiaonanshan have been discov-ered in this belt,raising the concern of geologists gradually.Based on the systematical summary and analysis of geochemical data,the author mainly carried out the research on geochemical char-acteristics of the Cu-Ni (PGE)ore-bearing mafic-ultramafic rocks belt.The ore-bearing intru-sions are formed in the range of 314—269Ma,indicating that they should be the products in late Variscan era.Most of rocks belong to tholeiitic series,and parts of rocks are calc-alkaline series in petrochemical composition.Gabbros and pyroxenites show two types of REE patterns:rela-tively flat REE patterns with inconspicuous fractionation of LREE and HREE,and rightward ob-lique linear REE patterns with LREE enrichment in relative to HREE (LaN/YbN is 1.49 to 20.08),and exhibit positive Eu anomaly or negative anomaly (δEu is 0.56 to 1.66);Pyroxene peridotites also show LREE-enrichment (LaN/YbN is 5.56 to 13.57)and HREE relatively flat, right-inclined REE distribution pattern,and display negative Eu anomaly (δEu is 0.57 to 0.83). Overall,all rocks show rightward oriented linear REE patterns with LREE enrichment in relative to HREE and exhibit a regular ΣREE decrease from gabbros to pyroxene peridotites,and are characterized by negative HFSE (Nb,Ta,Zr)anomalies.According to these geochemical char-acteristics,it may be inferred that all of the ore-bearing intrusions in this belt may come from the same source of magma,and magmatic assimilation occurs in the evolution.With high MgO and low-alkaline,the intrusions show high Mg# value and high m/f ratios,which indicates good pros-pecting potential.