Biotite compositions and geochemistry of porphyry-related systems from the central Urumieh Dokhtar Magmatic Belt, western Yazd, Iran: Insights into mineralization potentia
Biotite compositions and geochemistry of porphyry-related systems from the central Urumieh Dokhtar Magmatic Belt, western Yazd, Iran: Insights into mineralization potentia
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伊朗亚兹德西部乌鲁米赫多赫塔尔岩浆带中部斑岩相关系统的黑云母成分和地球化学：对成矿潜力的见解
DOI：
10.1016/j.lithos.2022.106593
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发表时间：
2022
期刊：
影响因子：
3.5
通讯作者：
Katsuhiko Suzuki
中科院分区：
文献类型：
--
作者：
Amir Taghavi;Mohammad Maanijou;David R. Lentz;Ali A. Sepahi-Gerow;Teruyuki Maruoka;Wataru Fujisaki;Katsuhiko Suzuki
通常，黑云母作为一种次要的造岩矿物出现在各种长英质到中度侵入岩中。由于其复杂的晶体结构允许多种元素的多位点替换，它可以记录母岩浆的物理化学条件。对整个岩石和黑云母的地球化学研究（使用 EPMA 和 LA-ICP-MS 方法）以及黑云母的岩相分析可以区分亚兹德西部贫瘠和肥沃的花岗岩。肥沃层系的特点是富含硅和镁（3.47–4.35，平均 3.75a.p.f.u.）和总稀土元素贫乏的黑云母。相比之下，贫瘠岩石中的 Fe（2.66–3.15，平均 3.08a.p.f.u.）、Al、Ti 和 REE（特别是 HREE+Y）增加。根据黑云母地压测量，肥沃的岩石（Darezereshk 斑岩铜矿床 (PCD)）在低压（约 0.6 kb，即次火山岩）下凝固；相比之下，贫瘠的岩石（Galvic 和 Shirkouh 花岗闪长岩）在较高压力（1.1 至 3.6 kb）下结晶。据推断，肥沃花岗岩的温度约为 750 °C，而贫瘠花岗岩的 T 为 625–675 °C。肥沃组在 Ni-NiO 缓冲区附近具有氧化还原特性，而贫瘠组在石英-铁橄榄石-磁铁矿 (QFM) 缓冲区附近则还原程度更大。因此，黑云母主元素成分、肥沃的岩浆体比贫瘠的侵入体处于更高的温度和更低的氧化还原压力（次火山）下。全岩地球化学特征表明，贫瘠层和肥沃层均以过铝质到准铝质花岗岩到闪长岩为代表，具有钙碱性特征，具有 I 型火山弧 (VAG) 构造环境。然而，肥沃岩层起源于具有钙碱性亲和力的地幔-地壳混合岩浆，而贫瘠岩层主要源自大陆地壳的再循环。
Commonly biotite occurs as a minor rock-forming mineral in a wide range of felsic to intermediate intrusive rocks. It can record the physicochemical conditions of the parent magma due to its complex crystal structure that allows multiple site substitutions of a wide range of elements. Geochemical studies of whole rocks and biotite (using EPMA and LA-ICP-MS methods) with petrographic analysis of biotite provide distinction between barren and fertile granitoids in western Yazd. Fertile suites are characterized by Si- and Mg-rich (3.47–4.35,ave. 3.75a.p.f.u.) and total REE-poor biotite. In contrast, Fe (2.66–3.15,ave. 3.08a.p.f.u.), Al, Ti, and REEs (in particular HREE+Y) increase in barren rocks. On the basis of biotite geobarometry, the fertile rocks (Darezereshk Porphyry Copper Deposit (PCD)) solidified at low pressure (ca. 0.6 kb, i.e., subvolcanic); in contrast, the barren rocks (Galvic and Shirkouh granodiorites) crystallized at higher pressures (1.1 to 3.6 kb). The temperature of the fertile granitoids is inferred to be about 750 °C, whereas T's of 625–675 °C for barren granitoids. The fertile suites have redox characteristic near the Ni-NiO buffer, whereas the barren suites are more reduced, near the quartz-fayalite-magnetite (QFM) buffer. Therefore, biotite major-element compositions, fertile magma bodies are emplaced at higher temperature and redox to lower pressures (subvolcanically) than the barren intrusive bodies. The whole-rock geochemical signatures show that both barren and fertile suites are represented by peraluminous to metaluminous granite to diorite that have calc-alkaline characteristics with an I-type volcanic arc (VAG) tectonic setting. However, fertile suites originated from the mantle-crust mixed magma exhibiting calc-alkaline affinity, whereas the barren suites are derived predominantly from recycling of continental crust.