摘要
华北地台南缘原划分的华熊地体可进一步划分出小秦岭、崤山、熊耳山和鲁山4个地体 ,它们之间均由NE -NNE向边界断裂所分隔 ,在基底地层层序、岩石组合、岩石主元素和稀土元素、岩浆作用和成矿作用以及地球物理特征等方面存在一系列差异。它们先经历了各自独立的形成过程 ,后在 185 0± 15 0Ma的中岳运动中 ,这些分散的范围较小的火山活动中心所形成的地体才逐渐拼贴在一起构成了华熊联合地体。
Huaxiong terrane at the southern margin of North China Plateform can be further subdvided into four terranes from west to east as follows: Xiaoqinling, Xiaoshan, Xiongershan and Rushan terranes, separated by NE-NNE direction faults between them. The boundary faults between these terranes are large deep faults which were developed under the deep structural settings such as crust mantle transitional zones and were active for a long time with newer and older components combined. These terranes are different in terms of stratigraphic sequences, rock assemblages, major elements and REE of rocks, magmatism, metallogeny and geophysics. The basement rocks of Xiaoqinling terrane mostly consist of metasediments. Among the volcanics the intermediate basic rocks predominate over the ultramafites. These rocks are strongly migmatized. Developed multiphase-multigenesis granites, pegmatite dikes, diabase dikes, and considerable number of gold bearing quartz veins, rock quartz, graphite, lennilite, phosphorite, marble and skarn type iron deposits. The metasedimentary rocks have a right slant LREE-enriched REE pattern. The clastic rocks are of higher Si amd Na, and lower Ti, Fe 2+ , Mg, Ca and K, revealing that the crust basicity was relatively low at that time. The volcanic rocks are of higher Fe 2+ and Mg, and lower Fe 3+ , with a gentle REE pattern and higher δEu. The corresponding rocks are similar to Condie's TH 1 type, Ⅰ type andesite and F Ⅱ type dacite-rhyolite respectively. The porphyries and related molybdenum (-tungsten) deposits developed in the cover strata. The basement of Xiaoshan terrane is thin, with few ultramafites. The metamophic grade is low. The magmatic activity is weak. Developed a few gold deposits. The metasediments and volcanics have the V type or weak U type REE pattern, with higher REE, (La/Yb) N and sharp negative Eu anomaly. The volcanic rocks are rich in Si, Fe 3+ , alkalies and Al, and depleted in Mg, Ti, Ca and Fe 2+ . The sedimentary rocks are depleted in Al, Fe 2+ , Mg and Ca. These factors reveal that its crust basicity was low, and its forming enviorment was similar in to the ancient craton. The multiphase porphyries and related molybdenum, tungsten and polymetallic deposits are found in the cover strata, mainly in Guandaokou Group. The basement of Xiongershan terrane has a large proportion of volcanics, among which the intermediate basic rocks and ultramafites are abundant. Developed the Yanshanian transformation type granitoids, densely populated syntexis type small porphyry bodies and explosive breccia pipes, and related gold-molybdenum deposits. The volcanic rocks have higher Mg, REE, (La/Yb) N and (Gd/Yb) N, and more distinct right slant REE pattern. The corresponding rocks are similar to Condie's TH 2 type and Ⅱ type andesite. The clastic rocks are of lower Si and Fe 3+ , and higher Al, Fe 2+ , Cu and Mg, indicating the lower degree of maturity of crust. The forming enviroment was closer to the ocean.The altered shearing zone type and quartz vein type gold deposits developed in the lower cover (Xionger Group), and the Yanshanian porphyries and related molybdenum tungsten deposits developed in the upper cover (manily Luanchuan Group). The basement of Rushan terrane contains more carbonate rocks and BIF. Developed graphite, lennilite and iron mineralizations, and weak magmatism. The volcanic rocks have higher Si, Ti, Na and Fe 3+ , lower Mg, K, Ca, Fe 2+ , and relatively flat REE pattern, without Eu- anomaly. The mafic rocks are similar to Condie's TH 1 type. The pelites are of higher Mg and Ca, and lower Al and Fe 2+ . The large scale and multiphase granitoids developed between Xionger Group and Kuanpin Group in the southern part of Rushan terrane. These separated, small scale terranes, formed by the volcano sedimentation centers,were amalgamated togather to form a combined terrane —— the Huaxiong amalgamation terrane during the Zhongyue movement at 1850±150Ma.
出处
《高校地质学报》
CAS
CSCD
1999年第4期426-440,共15页
Geological Journal of China Universities
基金
国家自然科学基金!重大项目 ( 4 973 3 12 0 )
博士点基金项目
关键词
边界断裂
基底地层
地球化学
成矿作用
boundary faults, basement strata, geochemistry, magmatism, metallogeny, Huaxiong amalgamtion terrane.
