当前位置: X-MOL 学术Miner. Deposita › 论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
Geology and genesis of the Shalipayco evaporite-related Mississippi Valley-type Zn–Pb deposit, Central Peru: 3D geological modeling and C–O–S–Sr isotope constraints
Mineralium Deposita ( IF 4.8 ) Pub Date : 2021-01-07 , DOI: 10.1007/s00126-020-01029-w
Saulo B. de Oliveira , Craig A. Johnson , Caetano Juliani , Lena V. S. Monteiro , David L. Leach , Marianna G. N. Caran

The Shalipayco Zn–Pb deposit, in central Peru, is composed of several stratabound orebodies, the largest of which are the Resurgidora and Intermedios, contained in carbonate rocks of the Upper Triassic Chambará Formation, Pucará group. Petrography suggests that a single ore-forming episode formed sphalerite and galena within vugs, open spaces, and fractures. Three-dimensional (3D) geological modeling has allowed division of the Chambará Formation into four members (Chambará I, II, III, and IV) that better define lithological controls on sulfide formation. Diagenetic replacement of evaporite minerals with the organic matter (OM) presence likely generated secondary porosity and H2S accumulation by bacterial sulfate reduction (BSR), providing ground preparation for the later Zn–Pb mineralizing event. The least-altered host rocks have C–O isotope compositions of 1.8 ± 0.1‰ (VPDB) and 29.9 ± 2.1‰ (VSMOW), respectively, within the Triassic marine carbonate ranges. Early dolomite contains lighter C–O composition (1.1 ± 0.9 and 23.8 ± 2.9‰, respectively) consistent with OM decomposition during burial diagenesis. Post-mineralization calcite has still lighter C–O composition (− 5.1 and 13.3‰, respectively), suggesting meteoric water that had migrated through organic-rich strata. The strontium isotopes of Mitu group basalts (0.709654–0.719669) indicate it as a possible, but not the unique source of strontium and probably of other metals. Highly negative sulfide sulfur isotope values (− 23.3 to − 6.2‰ (VCDT)) indicate a major component of the ore sulfur derived ultimately from BSR. However, multiple lines of evidence suggest that preexisting H2S underwent thermochemical redox cycling prior to ore formation. The influx of hot metalliferous brines to dolomitized zones containing trapped H2S is the preferred model for ore deposition at Shalipayco.

中文翻译:

Shalipayco 蒸发岩相关的密西西比河谷型 Zn-Pb 矿床的地质和成因,秘鲁中部:3D 地质建模和 C-O-S-Sr 同位素约束

Shalipayco Zn-Pb 矿床位于秘鲁中部,由几个层状矿体组成,其中最大的是 Resurgidora 和 Intermedios,包含在 Pucará 组上三叠统 Chambará 组的碳酸盐岩中。岩相学表明,一个单一的成矿事件在洞穴、开放空间和裂缝中形成了闪锌矿和方铅矿。三维 (3D) 地质建模允许将 Chambará 组划分为四个成员(Chambará I、II、III 和 IV),从而更好地定义对硫化物形成的岩性控制。蒸发岩矿物与有机质 (OM) 存在的成岩置换可能通过细菌硫酸盐还原 (BSR) 产生次生孔隙和 H2S 积累,为后期 Zn-Pb 矿化事件提供地面准备。在三叠纪海相碳酸盐岩范围内,变化最小的主岩的 C-O 同位素组成分别为 1.8 ± 0.1‰ (VPDB) 和 29.9 ± 2.1‰ (VSMOW)。早期白云岩含有较轻的 C-O 成分(分别为 1.1 ± 0.9 和 23.8 ± 2.9‰),与埋藏成岩过程中的 OM 分解一致。矿化后方解石的 C-O 成分仍然较轻(分别为 - 5.1 和 13.3‰),表明大气水已经迁移到富含有机物的地层。米图族玄武岩的锶同位素 (0.709654–0.719669) 表明它可能是锶的唯一来源,也可能是其他金属的唯一来源。高度负的硫化物硫同位素值(- 23.3 至 - 6.2‰ (VCDT))表明矿石硫的主要成分最终来自 BSR。然而,多条证据表明,在矿石形成之前,预先存在的 H2S 经历了热化学氧化还原循环。含金属的热卤水涌入含有截留 H2S 的白云石化区域是 Shalipayco 矿石沉积的首选模型。
更新日期:2021-01-07
down
wechat
bug