WELCOME to the Mag.I.C project!
MagIC – Petrology and Geochemistry of Igneous Rocks from Macao: Implications for the Crustal Evolution of Southern China / 澳门火成岩之岩石学与地球化学—对华南地壳演化的影响)
This project aimed to develop a detailed digital cartographic map of the igneous rocks of Macao, useful for professionals from different areas and to understand the geological history of the territory. The main results included: (1) absolute age determination from Macau magmatic events; (2) based on mineralogical and geochemical studies we have constrained the magma evolution and; (3) we contributed to a deeper understanding of the South China tectono-magmatic evolution.
Project reference: FDCT 043/2014/A1 (2014-2018)
updated on Mar 2021
Igneous rocks, in particular granitic ones, are of utmost importance to assess the tectonothermal evolution of continents and to decipher their geodynamic setting. During Mesozoic ages, the Southeastern China region (Cathasya block), where Macao is localized, was affected by granitic plutonism generated during the Indosinian (Triassic) and Yanshanian orogenies (Jurasic-Cretaceous), overprinting all previous events in the South China Fold Belt (SCFB). In Macao, the most complete document reporting the geology of the territory was published, in 1992, under Luísa Ribeiro coordination, the consultant of this project. It consists of the Macao Geological Map 1:5000 scale, and its memoir, where the main geological units and structures of Macao were presented. Until the beginning of this project proposal, there was a significant gap in the knowledge of the geology and geodynamic evolution of Macao compared with surrounding areas. The geology of Hong Kong and Guangdong (also included in the Cathaysia block) has been the subject of numerous SCI publications. In contrast, there were no SCI publications on the geology of Macao. To fill this gap, this project focused in obtaining new scientific knowledge about the origin and evolution of the territory of Macao, and also to spread and publish this new knowledge within the local and international scientific community. In his project, we developed a new trilingual digital geological map of Macao and, among several new scientific discoveries accomplished along the execution of the work, we emphasize the determination of the age of Macao magmatic rocks as well as of its geodynamic evolution. Briefly, Macao granites were emplaced in two main periods ranging from 164.5 ± 0.6 Ma to 162.9 ± 0.7 Ma and 156.6 ± 0.2 Ma to 155.5 ± 0.8 Ma, separated by ca. 6 Ma. Inherited zircons point to the existence of a basement with ages up to Paleo-Proterozoic and late Archean in the region. In addition, younger dacitic rocks were dated at 150.6 ± 0.6 Ma and <120 Ma. Macao granitic suite was incrementally assembled during a period of ca. 9 Ma and the transition from granitic magmatism (Middle to Upper Jurassic) to the younger dacite dykes (Upper Jurassic to Lower Cretaceous) most likely correspond to a change in the regional tectonic setting. Isotope and geochemical compositions together with model ages and mixing modelling strongly suggest that Macao granitic magmas were generated by partial melting of infracrustal medium-to-high K basaltic Paleo-Proterozoic to Mesoproterozoic protoliths heated by, and mixed to some degrees with, the contemporaneous underplating and/or intrusion of hot, mantle-derived magmas. The Jurassic Macao granites are interpreted as being produced in an intraplate extensional setting related to the foundering of a previously flat-slab (Paleo-Pacific plate) beneath SE China continent.
在这个项目所取得的一系列新科学发现中，我们会重点强调澳门岩浆岩年龄的厘定及其地球动力学的演化过程。总的来说，澳门的花岗岩侵入活动主要分为两期,164.5 ± 0.6 Ma（百万年）到 162.9 ± 0.7 Ma为第一期， 156.6 ± 0.2 Ma 到155.5 ± 0.8 Ma为第二期，中间相隔约6Ma。花岗岩中的继承锆石指示该地区存在着一个古元古代至晚太古代的古老基底。此外，也发现更年轻的英安质岩石的年龄为150.6 ± 0.6 Ma和<120 Ma。澳门的花岗岩套是在一个约9Ma的时期内逐步侵位形成的，从中晚侏罗纪的花岗质岩浆活动向晚侏罗-早白垩的英安质岩墙的转变很可能对应于区域构造环境的变化。
With field visits and samples:
MPS – Macau Professional Services, Limited, Macau
LECM – Macau Laboratory of Civil Engineering / 澳門土木工程實驗室, Macau
LNEG – Laboratório Nacional de Energia e Geologia (Laboratório de Geologia e Minas), Portugal
CGGC – China Gezhouba Group Corporation, Macau
Macau Golf and Country Club / 澳門高爾夫球鄉村俱樂部, Macau
SMG – Macao Meteorological and Geophysical Bureau / 地球物理暨氣象局, Macau