Two episodes of REEs mineralization at the Sin Quyen IOCG deposit, NW Vietnam
Two episodes of REEs mineralization at the Sin Quyen IOCG deposit, NW Vietnam
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DOI：
10.1016/j.oregeorev.2020.103676
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发表时间：
2020-10
影响因子：
3.3
通讯作者：
X. Ngo;Xin-Fu Zhao;T. Tran;Xiao-Dong Deng;Jian-wei Li
中科院分区：
文献类型：
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作者：
X. Ngo;Xin-Fu Zhao;T. Tran;Xiao-Dong Deng;Jian-wei Li
越南西北部的新泉氧化铁-铜-金（IOCG）存款已探明储量为5280万吨矿石，含铁14%、铜0.91%、稀土0.7%（稀土元素）和Au 0.44 g/t。稀土矿化位于钙硅酸盐蚀变带内，并与片麻岩、云母片岩和上Sin Quyen组大理石中的Fe-Cu矿体有关。两个矿化幕识别的基础上的领域和岩相关系。第一幕包括钠化蚀变（I-1期）、钙化蚀变及伴生稀土矿化（I-2期）和局部K-Fe蚀变（I-3期）。第二幕为主阶段矿化，包括四个主要蚀变阶段：成矿前钠化（II-1期），钙铁蚀变及伴生的铁稀土矿化（II-2期），K-Fe蚀变及伴生的Cu-Au矿化（II-3期），以及石英碳酸盐脉的最后碳酸盐阶段（II-4期）横切上述蚀变相和矿石，第1幕的原生褐帘石和1型钛铁矿（TNT-1）产出加权平均206 Pb/238 U年龄分别为882 ± 3 Ma和881 ± 8 Ma（2σ），反映了稀土成矿时代为第1幕。与铁氧化物和铜金矿共生的次生褐帘石和2型钛铁矿（TNT-2）的U-Pb年龄分别为840 ± 7 Ma和838 ± 5 Ma（2σ）。因此，这些年龄被认为代表了第2幕多金属IOCG矿化的时间。~880 Ma的钛铁矿颗粒εNd（t）值介于−7.00 ~ −5.43之间，介于新元古代长英质侵入岩和赋矿变质沉积岩之间，可能反映了岩浆流体与赋矿岩石之间的相互作用。相比之下，~840 Ma的钛铁矿的εNd（t）值介于−4.31至−1.97之间，与新元古代长英质侵入体的εNd（t）值相似，表明第II幕IOCG成矿作用可能是岩浆流体来源。在新元古代沿扬子地块西缘沿着俯冲过程中，与弧后伸展有关的长期构造活动可能形成了新泉多期矿化。
The Sin Quyen iron oxide-copper–gold (IOCG) deposit in northwestern Vietnam contains a proven reserve of 52.8 Mt ores at 14% Fe, 0.91% Cu, 0.7% REEs (rare earth elements), and 0.44 g/t Au. REEs mineralization is hosted within Ca-silicate alteration zone and associated with Fe-Cu ore bodies in the gneiss, mica schist, and marble of the Upper Sin Quyen Formation. Two mineralization episodes are identified based on the field and petrographic relations. The first episode includes sodic alteration (stage I-1), calcic alteration and associated REE mineralization (stage I-2), and localized K-Fe alteration (stage I-3). The second episode is main stage mineralization and contains four main stages of alteration: pre-ore Na alteration (stage II-1), Ca-Fe alteration and the associated Fe-REE mineralization (stage II-2), K-Fe alteration and associated Cu-Au mineralization (stage II-3), and the final carbonate stage of quartz-carbonate veins (stage II-4) crosscutting the above-mentioned alteration phases and ores.Primary allanite and type 1 titanite (Tnt-1) from episode 1 yield weighted mean206Pb/238U ages of 882 ± 3 Ma and 881 ± 8 Ma (2σ), respectively, which are interpreted as the timing of REE mineralization in episode 1. Secondary allanite and type 2 titanite (Tnt-2) associated with iron-oxide and Cu-Au ores, however, have U-Pb ages of 840 ± 7 Ma and 838 ± 5 Ma (2σ), respectively. These ages are hence considered to represent the timing of polymetallic IOCG mineralization in episode 2. ~880 Ma titanite grains have εNd(t) values ranging from −7.00 to −5.43, which are intermediate between the Neoproterozoic felsic intrusions and ore-hostingmeta-sedimentary rocks in the region and likely reflect interaction between magmatic fluids and ore-hosting rocks. In contrast, ~840 Ma titanite have εNd(t) values ranging from −4.31 to −1.97, similar to those of the Neoproterozoic felsic intrusions, indicating a possible magmatic fluid source for the episode II IOCG mineralization. Multiple episodes of mineralization at Sin Quyen were likely formed during the prolonged tectonothermal events related to backarc extension during the Neoproterozoic subduction along the western margin of the Yangtze Block.