Origins of ultramafic rocks in the Sulu Ultrahigh-pressure Terrane, Eastern China
Origins of ultramafic rocks in the Sulu Ultrahigh-pressure Terrane, Eastern China
复制标题
中国东部苏鲁超高压地体超镁铁质岩的成因
DOI：
10.1016/j.lithos.2012.12.003
复制
发表时间：
2013-09
期刊：
影响因子：
3.5
通讯作者：
Jian Wang
中科院分区：
文献类型：
--
作者：
Zhipeng Xie;Keiko Hattori;Jian Wang
苏鲁超镁铁岩与高压和超高压岩石共生，后者是扬子板块北方边缘变质的产物。这些超镁铁岩是重要的，因为它们提供了有关中生代碰撞带的性质和演化的信息。选取苏鲁带中部洋口湾、梭罗树和胡家林超镁铁岩。YKB和SLS中的超镁铁质岩石水化形成蛇纹岩，它们含有低浓度的中等不相容元素（Al，Ti和V），高含量的Ir族铂族元素（IPGE; Ir，Os和Ru;总量为12.8-21.7 ppb），以及高比例（1.2-5.5）的IPGE与Pd族PGE（PPGE）在整体岩石中。尖晶石含有高Cr（Cr# = Cr/[Cr + Al]的原子比，0.57-0.79）。这些数据表明，它们可能代表了华北陆缘的水合弧前地幔橄榄岩。来自HJL的纯橄榄岩样品未完全水合，烧失量（LOI）值为6.6至13.2重量%，并且含有具有高镁橄榄石组分（Fo = 100 × Mg/[Mg + Fe]，91.7-92.4）和NiO含量（0.36-0.41重量%）的橄榄石颗粒。尖晶石晶粒显示高Cr#（0.68-0.76）。大块岩石含有高IPGE（总量为5.0-22.7 ppb），并显示出IPGE与PPGE的高比率（高达8.8）。这些数据表明，它们也是在俯冲背景下高度流入部分熔融后残留的地幔橄榄岩。蛇纹岩和纯橄榄岩样品的地球化学特征不同于作为年轻火山岩捕虏体带到地表的新生代陆下岩石圈地幔（SCLM）的橄榄岩。相反，我们的样品是类似的，但更难熔的橄榄岩的残余太古代SCLM以下的NCC被封闭的古生代-中生代火成岩包体。因此，所研究的超镁铁岩可能代表旧的耐火岩石圈地幔橄榄岩的遗迹，在与YZC碰撞前的大洋岩石圈俯冲过程中，在NCC的边缘进行部分熔融。弧前地幔中的橄榄岩在中生代扬子克拉通俯冲到华北克拉通之下的过程中被拖入俯冲通道，并与苏鲁带中的浮花岗质变质岩一起被折返。
Ultramafic rocks in the Sulu belt are associated with high-pressure (HP) and ultra-high-pressure (UHP) rocks, a metamorphic product of the northern margin of the Yangtze Craton (YZC). These ultramafic rocks are important because they provide information relevant to the nature and evolution of the Mesozoic collisional belt. We selected ultramafic rocks from Yangkou Bay (YKB), Suoluoshu (SLS) and Hujialin (HJL) in the central region of Sulu belt. The ultramafic rocks in YKB and SLS are hydrated to form serpentinites and they contain low concentrations of moderately incompatible elements (Al, Ti, and V), high contents of Ir-group platinum-group elements (IPGE; Ir, Os, and Ru; 12.8–21.7 ppb in total), and high ratios (1.2–5.5) of IPGE to Pd-group PGE (PPGE) in bulk rocks. Spinel contains high Cr (Cr# = atomic ratio of Cr/[Cr + Al], 0.57–0.79). The data suggest that they likely represent hydrated forearc mantle peridotites underlying the margin of the North China Craton (NCC). Dunite samples from HJL are not fully hydrated with loss on ignition (LOI) values ranging from 6.6 to 13.2 wt.%, and contain olivine grains with high forsterite components (Fo = 100*Mg/[Mg + Fe], 91.7–92.4) and NiO contents (0.36–0.41 wt.%). Spinel grains show high Cr# (0.68–0.76). The bulk rock contains high IPGE (5.0–22.7 ppb total) and show high ratios (up to 8.8) of IPGE to PPGE. The data suggest that they are also residual mantle peridotites after high degrees of influx partial melting in the subduction setting. The geochemical features of our serpentinite and dunite samples are different from peridotites of young Cenozoic subcontinental lithospheric mantle (SCLM) that have been brought to the surface as xenoliths of young volcanic rocks. Instead, our samples are similar but even more refractory than peridotites of relict Archean SCLM below the NCC that were enclosed as xenoliths in Paleozoic–Mesozoic igneous rocks. Thus, the studied ultramafic rocks likely represent the relic of old refractory lithospheric mantle peridotites that underwent partial melting in the margin of the NCC during the subduction of oceanic lithosphere before the collision with the YZC. The peridotites in the forearc mantle were dragged into the subduction channel during the Mesozoic subduction of the YZC below the NCC, and exhumed together with the buoyant granitic metamorphic rocks in the Sulu belt.
登录
查看更多内容
巴塔哥尼亚最南端巴利艾克火山田下方古生代次大陆岩石圈地幔氧化态
影响因子：
3.5
作者：
Wang, Jian;Hattori, Keiko H.;Li, Jianping;Stern, Charles R.
通讯作者：
Stern, Charles R.
影响因子：
3.4
作者：
Tsai;Liou;Ernst
通讯作者：
Tsai;Liou;Ernst
影响因子：
5
作者：
K. Righter;A. Campbell;M. Humayun;R. Hervig
通讯作者：
K. Righter;A. Campbell;M. Humayun;R. Hervig
影响因子：
3.4
作者：
Zhang;Liou;Yang;Yui
通讯作者：
Zhang;Liou;Yang;Yui
影响因子：
2.7
作者：
S. Wallis;A. Ishiwatari;T. Hirajima;K. Ye;J. Guo;D. Nakamura;T. Kato;M. Zhai;M. Enami
通讯作者：
S. Wallis;A. Ishiwatari;T. Hirajima;K. Ye;J. Guo;D. Nakamura;T. Kato;M. Zhai;M. Enami