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大陆地壳的生长速率和地壳生长的位置均是地球科学中的最基本的问题。现有的许多大陆地壳生长模式认为 ,90 %的大陆地壳生长于 18亿年以前 ,显生宙以来的地壳生长不到整个地壳的 10 % ,主要位于活动大陆边缘。近年来在兴蒙造山带发现大量具有新生地壳来源性质的花岗岩产生于 50 0~ 10 0Ma ,对上述传统看法提出了挑战。现有的Nd同位素资料表明 ,兴蒙造山带的显生宙花岗岩 ,不论形成于什么时代和什么构造背景 ,也不论属于何种成因类型 ,几乎都具有正ε(Nd ,t)值和年轻的Nd模式年龄tDM 。从西往东 ,随着时代逐渐变新ε(Nd ,t)值有逐渐降低的趋势。花岗岩的tDM同由蛇绿岩和岛弧杂岩记录的古亚洲洋扩张的时间基本一致。只有一些在新元古代微陆块上的花岗岩才显示负ε(Nd ,t)值和较老的tDM,反映了其源岩包括前寒武纪地壳同地幔来源物质的不同程度混合。兴蒙造山带的花岗岩具有地幔来源的ε(Nd ,t)值 ,说明这些花岗岩中有一部分 (例如加里东期和海西早期 )可能同板块俯冲作用有关 ,花岗岩的来源是被交代的地幔楔。而大面积的晚古生代—中生代花岗岩则可能是由 80 0~6 0 0Ma前俯冲的洋壳形成的新生大陆地壳在拉伸体制下部分熔融而成。如果情况是这样 ,显生宙就曾发生过大规模的地壳生长。板内岩浆活动 ,特别是
The growth rate of the continental crust and the location of crustal growth are all the most fundamental problems in earth science. Many of the existing continental crustal growth models suggest that 90% of the continental crust grew 1.8 billion years ago and the crust since the Phanerozoic did not grow to 10% of the entire crust, mainly on the active continental margin. In recent years, the discovery of a large number of granites with the origin of crust origin in the Xingmeng orogen has occurred from 50 to 100 Ma, posing challenges to the above traditional view. The available Nd isotopic data show that the Phanerozoic granites in the Xingmeng orogenic belt have almost any positive genetic ε (Nd, t) value and are young, regardless of age and tectonic setting, regardless of their genetic type Nd mode age tDM. From west to east, the value of ε (Nd, t) tends to decrease gradually as time goes on. The tDM of granite is consistent with that of the ancient Asian ocean recorded by ophiolite and island arc complex. Only some granites on the Neoproterozoic micro-continental blocks show negative ε (Nd, t) values and older tDM, reflecting different degrees of mixing of source rocks, including Precambrian crustal and mantle source materials. The ε (Nd, t) values of the mantle derived granitoids from the Xingmeng orogen indicate that some of these granites (such as the Caledonian and Early Hercynian) may be related to plate subduction. The source of the granites is the metamorphic mantle wedge . However, the large-area Late Paleozoic-Mesozoic granitoids may be formed by partial melting of the nascent continental crust formed by the subducting oceanic crust of 80 ~ 600 Ma in the extensional regime. If so, large-scale crustal growth has taken place in the Phanerozoic. Plate magma activity, especially