CAJ | 학술논문

多不杂矿床是班公湖-怒江缝合带上发现的第一处大型斑岩铜矿床.该矿床位于班公湖-怒江缝合带的北侧,羌塘地块的南缘.含矿斑岩体属花岗闪长斑岩,其SiO2含量为61.3796-67.73%,平均为65.16%;稀土元素总量为(41.4-94)× 10~(-6),LREE>HREE,属轻稀土元素富集型;微量元素特征表现为富集大离子不相容元素Rb、K、Th、Ba、La、Ce、Sr,亏损高场强元素Nb、Ta、P、Ti.含矿斑岩的稀土元素和微量元素特点反映出岛弧带的岩浆作用特征.含矿斑岩中锆石的U-Pb SHRIMP测年获得(120.9±2.4)Ma(MSWD=4.3)谐和年龄,代表了含矿斑岩的形成时代.6个辉钼矿样品的Re-Os模式年龄范围非常一致,其变化范围为(117.6±1.3)～(118.5±1.4)Ma,等时线年龄为(118.0±1.5)Ma(MSwD=0.30),代表了该矿床的成矿年龄.该矿床的形成时代对应于班公湖.怒江早白垩世期间的多岛弧-盆系演化时期,其形成环境类似于东南亚的多岛弧-盆系统.
다불잡광상시반공호-노강봉합대상발현적제일처대형반암동광상.해광상위우반공호-노강봉합대적북측,강당지괴적남연.함광반암체속화강섬장반암,기SiO2함량위61.3796-67.73%,평균위65.16%;희토원소총량위(41.4-94)× 10~(-6),LREE>HREE,속경희토원소부집형;미량원소특정표현위부집대리자불상용원소Rb、K、Th、Ba、La、Ce、Sr,우손고장강원소Nb、Ta、P、Ti.함광반암적희토원소화미량원소특점반영출도호대적암장작용특정.함광반암중고석적U-Pb SHRIMP측년획득(120.9±2.4)Ma(MSWD=4.3)해화년령,대표료함광반암적형성시대.6개휘목광양품적Re-Os모식년령범위비상일치,기변화범위위(117.6±1.3)～(118.5±1.4)Ma,등시선년령위(118.0±1.5)Ma(MSwD=0.30),대표료해광상적성광년령.해광상적형성시대대응우반공호.노강조백성세기간적다도호-분계연화시기,기형성배경유사우동남아적다도호-분계통.
The Duobuza porphyry copper deposit, the first large-size porphyry copper deposit discovered along the Bangong-Nujiang suture zone, is situated in the Duobuza tectonic-magmatic zone on the southern margin of the Qiangtang-Sanjiang massif. The main mineralized porphyry in the ore deposit is a granodiorite porphyry, whose SiO_2 content varies from 61.37% to 67.73%, 65.16% on the average. Its REE content is (41.4-94) × 10~(-6), and the LREE content is higher than the HREE content, suggesting the enrichment of LREE. As for trace ele ments, the porphyry shows enrichment of Rb, K, Th, Ba, La, Ce, Sr and depletion of Nb, Ta, P, Ti. The major, rare earth and trace elements of the mineralized porphyry have characteristics of volcanic rocks formed in the island arc. The zircon SHRIMP dating (14 samples) of Duobuza granodiorite porphyry gave ~(206)Pb/~(238)U con cordant ages from (116.5±4.6) Ma to (125.3±4.7) Ma, with a weighted mean age of (120.9 + 2.4) Ma, which indicates the age of the copper-mineralized porphyry rock. Meanwhile, the ~(187)Re and ~(187)Os content of molybdenite from the ore deposit was determined by Inductively Coupled Plasma Mass Sperctrometry (ICP MS), and the results show that the Re-Os model ages of the deposit are from (117.6 ± 1.3) to (118.5 ± 1.4) Ma, and its isochron age (118.0 + 1.5) Ma, which have accurately determined the timing of mineralization. The age of the ore deposit is consistent with the evolution of the Bange-Nujiang archipelagic arc-basin system in Early Cretaceous, implying that the Duobuza copper deposit was formed in an archipelagic are-basin system simi lar to the system of southeast Asia.