Early Permian mafic-ultramafic complexes in eastern Xinjiang （新疆） are mainly distributed in the Beishan （北山） area, Mid-Tianshan （天山） massif and Jueluotage （觉罗塔塔） belt. Systematic compositional mappin...Early Permian mafic-ultramafic complexes in eastern Xinjiang （新疆） are mainly distributed in the Beishan （北山） area, Mid-Tianshan （天山） massif and Jueluotage （觉罗塔塔） belt. Systematic compositional mapping of olivines from these Early Permian mafic-ultramafic complexes demonstrates that an apparently spatial distribution and heterogeneous partial melting in the mantle source exists from the Beishan area, across the Mid-Tianshan massif, to the Jueluotage belt from the south to the north. This is probably consistent with the spatial evolutional differences and tectonic features of these three belts. The decreasing degree of partial melting, as revealed by decreasing Fo contents of olivines, from south to north and from east to west reflects the southward subduction of the Paleo-Asian Ocean and the south location of the indistinct mantle plume in the Permian. Simultan ously, NiO and Fo-mapping in olivine also indicates that sulfide segregation before olivine crystallization played an important role in Ni-Cu mineralization in the mafic-ultramafic complexes. Olivines with the compositional range of Fo （77-86） and NiO （less than 0.22 wt.%） are more favorable for Ni-Cu sulfide mineralization.展开更多
巴音布鲁克盆地为天山中部的高海拔山间盆地,受控于多个气候系统,该区域全新世气候变化研究对探讨西风环流、季风环流的此消彼长具有重要意义。本研究以巴音布鲁克剖面110个地层样品为研究材料,基于AMS14C年代框架,以花粉为古气候代用指...巴音布鲁克盆地为天山中部的高海拔山间盆地,受控于多个气候系统,该区域全新世气候变化研究对探讨西风环流、季风环流的此消彼长具有重要意义。本研究以巴音布鲁克剖面110个地层样品为研究材料,基于AMS14C年代框架,以花粉为古气候代用指标,运用主成分分析(Principal Component Analysis,PCA),重建了研究区中、晚全新世的气候演变过程。结果表明,8660-6350 cal yr B.P.期间,以云杉属(Picea)、桦木属(Betula)为代表的乔木花粉含量高。同时,以禾本科(Poaceae)、蒿属(Artemisia)、藜科(Chenopodiaceae)为主的旱生草本繁育。推测研究区发育森林草原、河谷林,反映了相对暖湿的气候特征。6350-4850 cal yr B.P.期间,乔木花粉含量减少,陆生草本植物花粉含量上升。森林退缩,植被演替为干草原,表明湿度变小,温度降低。4850-2810 cal yr B.P.期间,云杉属、桦木属花粉含量接近消失,而耐旱的麻黄属(Ephedra)花粉含量增幅明显,陆生草本植物花粉含量高,湿生/水生植物花粉含量持续下降。古植被演化为荒漠草原,推测气候进入冷干期。4850-4050 cal yr B.P.期间,天山地区发生了以“冷干”为特征的气候突变现象,根据起讫时间、水热组合方式等特征判断是对4.2ka事件的响应。该现象的发生可能与太阳辐射、温盐环流有关,具体表现为:随着北半球65°太阳辐射减少,北大西洋浮冰增加,海水表层温度下降,导致温盐环流减弱甚至停滞,水汽蒸发量降低,西风携带的水汽骤减,使该区域突然变冷变干。展开更多
基金supported by the National Natural Science Foundation of China (Nos. 41030424,41173011)the Knowledge Innovation Program of the Chinese Academy of Sciences (No. KZCX2-YW-107)the China Postdoctoral Science Foundation to Benxun Su
文摘Early Permian mafic-ultramafic complexes in eastern Xinjiang （新疆） are mainly distributed in the Beishan （北山） area, Mid-Tianshan （天山） massif and Jueluotage （觉罗塔塔） belt. Systematic compositional mapping of olivines from these Early Permian mafic-ultramafic complexes demonstrates that an apparently spatial distribution and heterogeneous partial melting in the mantle source exists from the Beishan area, across the Mid-Tianshan massif, to the Jueluotage belt from the south to the north. This is probably consistent with the spatial evolutional differences and tectonic features of these three belts. The decreasing degree of partial melting, as revealed by decreasing Fo contents of olivines, from south to north and from east to west reflects the southward subduction of the Paleo-Asian Ocean and the south location of the indistinct mantle plume in the Permian. Simultan ously, NiO and Fo-mapping in olivine also indicates that sulfide segregation before olivine crystallization played an important role in Ni-Cu mineralization in the mafic-ultramafic complexes. Olivines with the compositional range of Fo （77-86） and NiO （less than 0.22 wt.%） are more favorable for Ni-Cu sulfide mineralization.
文摘巴音布鲁克盆地为天山中部的高海拔山间盆地,受控于多个气候系统,该区域全新世气候变化研究对探讨西风环流、季风环流的此消彼长具有重要意义。本研究以巴音布鲁克剖面110个地层样品为研究材料,基于AMS14C年代框架,以花粉为古气候代用指标,运用主成分分析(Principal Component Analysis,PCA),重建了研究区中、晚全新世的气候演变过程。结果表明,8660-6350 cal yr B.P.期间,以云杉属(Picea)、桦木属(Betula)为代表的乔木花粉含量高。同时,以禾本科(Poaceae)、蒿属(Artemisia)、藜科(Chenopodiaceae)为主的旱生草本繁育。推测研究区发育森林草原、河谷林,反映了相对暖湿的气候特征。6350-4850 cal yr B.P.期间,乔木花粉含量减少,陆生草本植物花粉含量上升。森林退缩,植被演替为干草原,表明湿度变小,温度降低。4850-2810 cal yr B.P.期间,云杉属、桦木属花粉含量接近消失,而耐旱的麻黄属(Ephedra)花粉含量增幅明显,陆生草本植物花粉含量高,湿生/水生植物花粉含量持续下降。古植被演化为荒漠草原,推测气候进入冷干期。4850-4050 cal yr B.P.期间,天山地区发生了以“冷干”为特征的气候突变现象,根据起讫时间、水热组合方式等特征判断是对4.2ka事件的响应。该现象的发生可能与太阳辐射、温盐环流有关,具体表现为:随着北半球65°太阳辐射减少,北大西洋浮冰增加,海水表层温度下降,导致温盐环流减弱甚至停滞,水汽蒸发量降低,西风携带的水汽骤减,使该区域突然变冷变干。
基金The Qilian Mountains,Eastern Tian Shan Snow Leopard Specialized Survey(2017092302)The Eastern Tien Shan Snow Leopard Specialized Survey(2018HXFWBHQ-SK-01)The Fundamental Investigation of Wild Animal and Plant Resources of Eastern Tianshan State Forestry Administration(XJSZG2022-102)。
