CAJ | 학술논문

辽宁西部广泛分布着晚中生代火山岩，横跨华北克拉通和兴-蒙造山带两大构造单元，一般认为它们是以在这一地区发育的两条主要断裂--西拉木伦河断裂和赤峰-开源断裂为界。这些火山作用曾被认为是中生代伊泽奈崎板块西向或西北向消减作用的结果。在岩性上它们主要以中酸性岩石为主，玄武岩等中基性岩石较少。为查明下伏岩石圈对这些岩浆作用成因的影响，对其中的SiO2含量<60％的中基性火山岩进行了详细的Sr-Nd-Pb同位素研究。结果显示，以西拉木伦河断裂和赤峰-开源断裂两侧为界，两侧火山岩的同位素特征存在显著区别。南区有明显的EMI特征并具EMI-PM混合趋势，而北区则显示了原始或略亏损的特征。南北两区之间的过渡带(介于西拉木伦河断裂和赤峰-开源断裂之间)则表现了同位素组成上相应的过渡特征。这一地球化学观测与已有的地质和地球物理资料颇为吻合。基于新生代幔源岩石化学反演的中国东部陆下地幔化学区划研究揭示了克拉通下(subcratonic)岩石圈地幔与EMI存在着密切关系。本研究所提供的地球化学证据说明了采用中生代中基性岩类作为类似研究途径的可行性，并进一步提出对华北克拉通边缘中生代火山作用成因另一种可能的解释，即古消减带物质的活化有可能对华北北缘火山岩源区物质组成产生重要影响。
료녕서부엄범분포착만중생대화산암，횡과화북극랍통화흥-몽조산대량대구조단원，일반인위타문시이재저일지구발육적량조주요단렬--서랍목륜하단렬화적봉-개원단렬위계。저사화산작용증피인위시중생대이택내기판괴서향혹서북향소감작용적결과。재암성상타문주요이중산성암석위주，현무암등중기성암석교소。위사명하복암석권대저사암장작용성인적영향，대기중적SiO2함량<60％적중기성화산암진행료상세적Sr-Nd-Pb동위소연구。결과현시，이서랍목륜하단렬화적봉-개원단렬량측위계，량측화산암적동위소특정존재현저구별。남구유명현적EMI특정병구EMI-PM혼합추세，이북구칙현시료원시혹략우손적특정。남북량구지간적과도대(개우서랍목륜하단렬화적봉-개원단렬지간)칙표현료동위소조성상상응적과도특정。저일지구화학관측여이유적지질화지구물리자료파위문합。기우신생대만원암석화학반연적중국동부륙하지만화학구화연구게시료극랍통하(subcratonic)암석권지만여EMI존재착밀절관계。본연구소제공적지구화학증거설명료채용중생대중기성암류작위유사연구도경적가행성，병진일보제출대화북극랍통변연중생대화산작용성인령일충가능적해석，즉고소감대물질적활화유가능대화북북연화산암원구물질조성산생중요영향。
Late Mesozoic volcanic rocks are extensively spread on both sidesof northern margin of the North China Craton (NCC), where is the boundary between an Archean craton to the south and a Paleozoic orogenic belt, Xing'an-Mongolia Orogenic Belt (XMOB), to the north. Two major east-west trending faults, Kaiyuan-Chifeng Fault (KCF) and Xar Moron He Fault (XHF) develop in this margin zone as a boundary between two tectonic domains. The volcanism has been thought to be the magmatic response to the west-, or northwest-dipping subduction of Izanagi Plate and covers a wide range in lithologies, from rhyolites, dacites, trachyte, andesites to basalts. To clarify the role of underlain lithosphere in magma genesis, a systematic Sr-Nd-Pb isotope survey has been taken on these selected samples that contain SiO2 < 60%, i.e. basalt, trachyandesite and basaltic andesite. The results show a distinctive and contrasting pattern of isotope signatures on two sides of the boundary faults, KCF and XHF. A remarked EMI signature and EMI-PM mixing trend feature the isotope system of basaltic volcanism on the southern side, the North China Craton, whereas the primitive to slightly depleted signature dominates that of basaltic volcanism on the northern side, the Paleozoic Orogenic Belt (XMOB). A clearly transitional and Variable signature has been shown in the area between two parallel EW trending faults, i.e. KCF and XHF. This picture is quite consistent with the available geological and geophysical observations. A chemical zoning of subcontinental mantle beneath eastern China (Zhou and Zhu, 1992) has shown the EMI affinity of sub-cratonic mantle based on a chemical inversion study of the Cenozoic mantle-derived rocks. However, a positive argument is presented to show that the magma sources of Mesozoic volcanic rocks in the region have been highly influenced by the underlain lithosphere although the magma has been evolved to different degrees. Furthermore, the results would support an alternative interpretation, reactivation of paleo-subduction zone, for the genesis of Mesozoic volcanic magmatism in this craton marginal area.