| 青藏高原北部全吉地块白垩纪煌斑岩脉群的发现及意义 |
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| 引用本文： | 王秉璋,陈静,张金明,李积清,白建海.青藏高原北部全吉地块白垩纪煌斑岩脉群的发现及意义[J].地球科学,2020,45(4):1136-1150. |
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| 作者姓名： | 王秉璋 陈静 张金明 李积清 白建海 |
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| 作者单位： | 青藏高原北部地质过程与矿产资源重点实验室, 青海省地质调查院, 青海西宁 810012 |
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| 基金项目： | 第二次青藏高原综合科学考察研究（STEP）项目2019QZKK0702国家自然科学基金项目41762006青海省重大科技专项2016-SF-A3 |
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| 摘 要： | 除陆相沉积盆地外，青藏高原北部白垩纪建造记录稀少，岩浆活动的研究极少，幔源岩浆活动十分罕见，在青藏高原北部全吉地块首次发现了白垩纪煌斑岩脉群，深入研究可深化认识高原北部中生代晚期地质过程.对分布在全吉地块东部沙柳泉地区的煌斑岩进行了大比例尺填图，主微量元素、Sr-Nd-Pb同位测定、锆石SHRIMP和LA-ICP-MS U-Pb年代学研究.煌斑岩中获得锆石U-Pb年龄分别为135.2±1.8 Ma和132.9±1.3 Ma.岩石具高钾（K2O=4.53%~5.25%）、镁（MgO=7.23%~12.27%）和低钛（0.85%~1.29%）的特点，为钾质钙碱性煌斑岩，Rb、Ba、Th、U和Pb等大离子亲石元素（LILE）富集，Nb、Ta和Ti等高场元素（HFSE）亏损，（87Sr/86Sr）i介于0.718 0~0.718 6.εNd（t）=-14.2~-14.4，208Pb/204Pb变化于38.414~39.334，207Pb/204Pb在15.632~15.681，206Pb/204Pb介于18.568~19.203，显示岩浆源于与洋陆俯冲作用影响有关的EMⅡ型地幔源，形成于南北拉张背景下沿深大断裂引起的岩石圈地幔局部部分熔融.岩石具有较高Au（平均值为6.8×10-9）和F（平均值2 450×10-6）浓度，对全吉地块东部金矿成矿作用十分有利.
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| 关 键 词： | 青藏高原 全吉地块 白垩纪 煌斑岩 EMⅡ型地幔源 岩石学 |
| 收稿时间： | 2019-06-09 |
Discovery and Significance of Cretaceous Lamprophyre Dike Group in Quanji Block of Northern Tibetan Plateau |
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| Abstract: | Cretaceous formation records are rare in the northern part of the Tibetan plateau, except for terrestrial sedimentary basins, with only few magmatic activities reported, let alone mantle-derived magmatic activities. The lamprophyres exposed in the Shaliuquan area, the eastern part of the Quanji block, were firstly discovered by field work, which were subjected to a large scale mapping, major and trace element analyses, precise zircon SHRIMP and LA-ICP-MS U-Pb dating and Sr-Nd-Pb isotopic measurements, aiming to deepen the understanding of the Late Mesozoic geological process in the northern plateau. The results yield the average zircon U-Pb ages of 135.2±1.8 Ma and 132.9±1.3 Ma. The rocks are rich in potassium (K2O=4.53%-5.25%), magnesium (MgO=7.23%-12.27%) and poor in titanium (0.85%-1.29%), showing potassium calc-alkaline. They are also enriched in large ion LILE elements (Rb, Ba, Th, U and Pb) and deficient in high field elements (Nb, Ta and Ti). (87Sr/86Sr)i value is 0.718 0-0.718 6. εNd(t) value is -14.2 to -14.4, 208Pb/204Pb is 38.414 to 39.334, 207Pb/204Pb is 15.632-15.681, and 206Pb/204Pb is 18.568-19.203. These data indicate the magma originated from the oceanic subduction-related EMⅡ mantle source and formed from local partial melting of the lithospheric mantle along the deep fracture. The high contents of Au (the mean of 6.8×10-9) and F (the mean of 2 450×10-6) of the lamprophyres are very favorable for gold mineralization in the eastern part of the Quanji block. |
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