El Zorro: early Jurassic intrusion-related gold (IRG) mineralization in the oldest, western-most segment of the Andean Cordillera of Northern Chile

IF 4.4 2区 地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS
Eduardo Fritis, Nicholas H. S. Oliver, Michael C. Rowe, Julie V. Rowland, Zeffron C. Reeves, Huiqing Huang
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Abstract

The El Zorro gold district is the most recent gold discovery in the Coastal Cordillera of northern Chile. Ternera is the largest deposit in the district with total resources currently estimated at 1.282 Moz. New geology, geochemistry and geochronology data indicate that hydrothermal mineralization is mostly hosted within felsic to intermediate, ilmenite-bearing calc-alkaline dikes and stocks of the Upper Triassic to Lower Jurassic Relincho Pluton, and some of the adjacent Devonian to Carboniferous metasediments of the Chañaral Epimetamorphic Complex. Sheeted veins, veinlets, and fault zones with quartz, low amounts of pyrite, pyrrhotite and arsenopyrite, and local calcite are surrounded by narrow haloes of albite-biotite-quartz ± sulfides-K-feldspar-sericite-chlorite. Gold (mostly in the veins) is associated with elevated W-Bi and also As-Te-Sn, and not with iron enrichment or base metals, even though this system is proximal (~ 20 km) to IOCG and IOA deposits of the Coastal Cordillera. The main phase of gold mineralization occurred soon after emplacement of tonalitic dikes and granodiorite from the Relincho and Cuevitas plutons (U–Pb zircon between ~ 205 and 190 Ma), about 80 m.y. later than the development of orogenic fabrics. An absolute upper age limit is provided by compositionally distinct ore-cutting mafic dikes dated at 175–170 Ma (U–Pb apatite). The deposit falls into the intrusion-related gold category, as indicated by the cutting of earlier orogenic fabrics, the metal and alteration associations, and the spatial and temporal connection to reduced ilmenite-series intrusions, which are also very similar geochemically to the ‘type-locality’ IRG intrusions of the Tintina Belt in Yukon/Alaska. The El Zorro gold district represents the oldest and geologically western-most mineralizing event in the Central Andes of northern Chile, consistent with its time–space placement within the tectonic framework of easterly-younging mineralization and igneous activity in the Chilean Cordillera.

Abstract Image

埃尔佐罗:智利北部安第斯科迪勒拉山系最古老、最西段的早侏罗世侵入相关金矿(IRG)成矿作用
埃尔佐罗金矿区是智利北部沿海科迪勒拉山系最新发现的金矿。Ternera 是该地区最大的矿床,目前估计总资源量为 1.282 兆焦耳。新的地质学、地球化学和地质年代数据表明,热液矿化主要赋存于上三叠统至下侏罗统雷林乔岩体的长英质至中英质、含钛铁矿的钙碱性尖晶石和岩浆中,以及邻近的泥盆纪至石炭纪的查纳拉尔表变质复合岩体的一些玄武岩中。片状矿脉、小矿脉和断层带中含有石英、少量黄铁矿、黄铁矿和砷黄铁矿以及局部方解石,周围环绕着白云石-黑云母-石英±硫化物-长石-绢云母-绿泥石的狭窄光环。金(主要在矿脉中)与W-Bi和As-Te-Sn的升高有关,而与铁富集或贱金属无关,尽管该系统距离海岸科迪勒拉山系的IOCG和IOA矿床很近(约20公里)。金矿化的主要阶段发生在Relincho和Cuevitas岩体的黑云母尖晶石和花岗闪长岩成岩后不久(U-Pb锆石在205-190Ma之间),比造山运动构造的形成晚了约80年。一个绝对的年龄上限是由成分独特的矿石切割黑云母尖晶石提供的,其年代为 175-170 Ma(U-Pb 磷灰石)。从早期造山构造的切割、金属和蚀变关联以及与还原钛铁矿系列侵入体的时空联系来看,该矿床属于与侵入有关的金矿类别,而这些侵入体在地球化学上与育空/阿拉斯加廷蒂娜带的 "类型-地点 "IRG侵入体非常相似。埃尔佐罗金矿区代表了智利北部中安第斯山脉最古老、地质学上最西部的成矿事件,这与其在智利科迪勒拉山系东渐成矿和火成岩活动的构造框架中的时空位置是一致的。
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来源期刊
Mineralium Deposita
Mineralium Deposita 地学-地球化学与地球物理
CiteScore
11.00
自引率
6.20%
发文量
61
审稿时长
6 months
期刊介绍: The journal Mineralium Deposita introduces new observations, principles, and interpretations from the field of economic geology, including nonmetallic mineral deposits, experimental and applied geochemistry, with emphasis on mineral deposits. It offers short and comprehensive articles, review papers, brief original papers, scientific discussions and news, as well as reports on meetings of importance to mineral research. The emphasis is on high-quality content and form for all articles and on international coverage of subject matter.
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