U-Pb Zircon Geochronology of Granitic Rocks from the Chuquicamata-El Abra Porphyry Copper Belt of Northern Chile: Excimer Laser Ablation ICP-MS Analysis
U-Pb Zircon Geochronology of Granitic Rocks from the Chuquicamata-El Abra Porphyry Copper Belt of Northern Chile: Excimer Laser Ablation ICP-MS Analysis
复制标题
DOI：
10.2113/gsecongeo.101.7.1327
复制
发表时间：
2006-11
期刊：
影响因子：
5.8
通讯作者：
I. Campbell;Julian R. Ballard;J. Palin;C. Allen;A. Faunes
中科院分区：
文献类型：
--
作者：
I. Campbell;Julian R. Ballard;J. Palin;C. Allen;A. Faunes
本研究报告了对智利北部丘基卡马塔-埃尔阿布拉斑岩铜矿带第三纪深成岩进行综合地质年代学研究的结果。通过准分子激光烧蚀-电感耦合等离子体质谱 (ELA-ICP-MS) 测定了来自 Los Picos-Fortuna-Pajonal-El Abra 复合火成岩杂岩体、Radomiro Tomic 矿和 Opache 矿区的 22 个侵入体的锆石 U-Pb 同位素年龄。 Pajonal-El Abra 复合体的测年样本显示，其年龄范围从 42.7 Ma 到 37.2 Ma，这表明侵入体的形成时间至少为 5.5 m.y.。其中只有最年轻的 El Abra 斑岩矿含有矿石。 Los Picos-Fortuna 综合体中的 5 个单元的年龄从 42.3 Ma 到 38.0 Ma 不等，没有一个单元具有显着的经济矿化作用。侵入岩中继承的锆石丰度随着年龄的降低而增加，这表明 Los Picos-Fortuna-Pajonal-El Abra 火成岩杂岩源区的岩浆活动从大约 55 Ma 开始稳步增加。在分析不确定性范围内，来自 Los Picos-Fortuna 火成岩杂岩体的五个测年单元与北部 Pajonal-El Abra 杂岩体中岩石学上相当的单元具有相同的年龄，支持了先前工作人员提出的相关性。由于这些复合体现在位于西裂隙的相对两侧，并且相距 35 公里，因此相关性限制了断层上大约 100 年后的净左旋位移。 33马。 Chuquicamata、El Abra、Radomiro Tomic 和 Opache 的含矿斑岩的年龄范围几乎为 5 m.y.。从 37.9 Ma 到 33.3 Ma。丘基卡马塔火成岩杂岩体的含矿侵入体厚度为 3.5 m.y。比 Los Picos-Fortuna-Pajonal-El Abra 火成岩杂岩体中最年轻的侵入体要年轻，这使得它们不太可能在基因上相关。另一方面，Opache 斑岩与 Los Picos-Fortuna 杂岩位于西裂隙的同一侧，并且与 El Abra 矿斑岩的年龄相同，可能是在该杂岩结晶的最后阶段形成的。
This study reports the results of a comprehensive geochronological study of Tertiary plutonic rocks in the Chuquicamata-El Abra porphyry copper belt of northern Chile. Zircon U-Pb isotope ages of 22 intrusions from the composite Los Picos-Fortuna–Pajonal-El Abra igneous complex, Radomiro Tomic mine, and Opache prospect were determined by excimer laser ablation-inductively coupled plasma-mass spectrometry (ELA-ICP-MS). The dated samples from the Pajonal-El Abra complex show a continuous age range from 42.7 to 37.2 Ma, indicating that the intrusions were emplaced over a period of at least 5.5 m.y. Only the youngest of these, the El Abra mine porphyry, is ore bearing. The five units that were dated from the Los Picos-Fortuna complex range in age from 42.3 to 38.0 Ma and none host significant economic mineralization. An increase in the abundance of inherited zircons with decreasing age in the intrusive rocks is interpreted to indicate that magmatic activity in the source region of the Los Picos-Fortuna–Pajonal-El Abra igneous complex increased steadily from about 55 Ma. The five dated units from the Los Picos-Fortuna igneous complex have the same age, within analytical uncertainty, as petrologically equivalent units in the Pajonal-El Abra complex to the north, supporting the correlation suggested by previous workers. Because these complexes are now on opposite sides of the West fissure and separated by 35 km, the correlation constrains the net sinistral displacement on the fault subsequent to ca. 33 Ma. Ore-bearing porphyries at Chuquicamata, El Abra, Radomiro Tomic, and Opache span an age range of almost 5 m.y. from 37.9 to 33.3 Ma. The ore-bearing intrusions of the Chuquicamata Igneous Complex are 3.5 m.y. younger than the youngest intrusions of the Los Picos-Fortuna–Pajonal-El Abra igneous complex, which makes it unlikely that they are genetically related. The Opache porphyry, on the other hand, which is on the same side of the West fissure as the Los Picos-Fortuna complex and has the same age as the El Abra mine porphyry, could have formed during the final stages of crystallization of that complex.