投稿时间：2023-09-03
修订日期：2024-03-11
网络发布日期：2024-04-25
中文摘要:宁芜玢岩型铁矿矿集区是中国东部重要的铁矿矿集区之一。宁芜矿集区在早白垩世135~126 Ma间连续发育了成分和源区相似的4组火山作用旋回，并伴随有两大类侵入岩发育：一类为辉石闪长玢岩-闪长玢岩，与玢岩型铁矿床的形成密切相关，主要发育于大王山火山旋回晚期（约131 Ma）；另一类为花岗岩类侵入岩，形成于铁矿化之后，成岩时代与姑山和娘娘山火山旋回相近（130~126 Ma）。两类侵入岩源区的差异与联系目前尚未揭露。本次研究通过对两类侵入岩锆石年代学、Hf-O同位素特征的研究，区分了不同侵入岩源区差异。结果表明，与成矿母岩同旋回侵入岩锆石的δ18O集中于6.0‰~6.5‰，εHf（t）集中于-6.0~-5.0；成矿后形成的花岗岩类侵入岩锆石的δ18O集中于7.0 ‰至8.0 ‰，εHf（t）分布于-8.7~-1.2。结合前人研究，区内岩浆活动存在有富集地幔、太古代地壳和新元古代地壳3个岩浆源区，4个火山作用旋回的岩浆源区在130 Ma左右发生了改变。130 Ma之前的龙王山和大王山火山旋回的岩浆岩源区主要为受太古代地壳混染的富集地幔，而130 Ma之后的姑山和娘娘山火山作用旋回的岩浆岩源区主要为受新元古代地壳混染的富集地幔。多阶段火山作用中只有大王山旋回的闪长玢岩与玢岩型铁矿的形成有关。相比较其他火山旋回，大王山旋回具有更高的富集地幔组分以及更少的新元古代地壳的混染。因而，岩浆中较高比例的富集地幔含量是控制玢岩型铁矿形成的关键因素之一。
Abstract:The Ningwu ore district is the best-defined iron oxide-apatite (IOA) district in China, which hosts more than 30 IOA deposits and is one of the important Fe resource areas in eastern China. Four groups of volcanic cycles (suits) with similar compositions and magma sources have been continuously developed in the Ningwu district during 135~126 Ma. Two major types of intrusions have been formed with the multi-stage volcanism. One type is pyroxene diorite porphyrite/diorite porphyrite, closely related to the formation of IOA deposits and mainly deve-loped in the late of the Dawangshan volcanic cycle (~131 Ma). The other type is granite rocks, formed after Fe mineralization and of a similar age to the volcanic cycles of the Gushan and Niangniangshan (130~126 Ma). The relationship and differences between these two types of intrusions have not yet been revealed. In this contribution, chronology and Hf-O isotope characteristics of zircons from these two types of intrusions have been studied, effectively distinguishing the differences in the magma sources of different intrusions. Zircons from the syn-mineralization intrusion rocks have a concentrated δ18O range of 6.0‰ to 6.5‰, with εHf(t) values between -6.0 and -5.0. In comparison, the zircons of the post-mineralization intrusions have a higher δ18O range of 7.0‰~8.0‰, with εHf(t) range of -8.7 to -1.2. The magma source transformation of multi-stage volcanism happened at~130 Ma. The source areas of volcanic and intrusive rocks formed in the Longwangshan and Dawangshan volcanism cycles (before 130 Ma) are mainly from the enriched mantle contaminated by the Archean crust. The source areas of volcanic and intrusive rocks formed in the Gushan and Niangniangshan volcanic cycles (after 130 Ma) are mainly from the enriched mantle contaminated by the Neoproterozoic crust. In multi-stage volcanic activity, only the Dawangshan cycle is related to the formation of IOA deposits. Compared to other volcanic cycles, the Dawangshan cycle has higher enriched mantle components and less contamination of the Neoproterozoic crust. Therefore, the higher enriched mantle content in the ore-forming parent rock is one of the key factors controlling the formation of IOA deposits.
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基金项目:本文得到国家重点研发计划（编号：2022YFC2903703）、国家自然科学基金项目（编号：42172102，41973022）和中央级公益性科研院所基本科研业务费专项资金（编号：KK2019）联合资助
引用文本：
段超,李延河,毛景文,王丛林,杨秉阳,侯可军,万秋,施珂,蔡杨,王倩,王天顺.2024.宁芜矿集区多阶段火山作用岩浆源区的转变:来自侵入岩锆石Hf-O同位素特征的记录[J].矿床地质,43(2):227~243DUAN Chao,LI YanHe,MAO JingWen,WANG CongLin,YANG BingYang,HOU KeJun,WAN Qiu,SHI Ke,CAI Yang,WANG Qian,WANG TianShun.2024.Magma source transformation of multi-stage volcanism in Ningwu ore district, eastern China:Evidence from zircon Hf-O isotopes of intrusions[J].Mineral Deposits43(2):227~243
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