Magnetic characteristics and their paleoclimatic significance of Fengzhou loess in the Qinling Mountains of China

The Fengzhou loess section is very typical in the Qinling Mountains. The section, about 82 m thick and underlain by the Neogene red clay, consists of 33 layers of loess and 33 layers of paleosol. The section covers Brunnes normal polarity zone and Matuyama reversed polarity zone, and the B/M boundary is located in the middle of L₈. Matuyama reversed polarity zone records Jaramillo, Olduvai and Reunion normal polarity subchrons. The boundary between Matuyama reversed polarity zone and Gauss normal polarity zone (M/Ga) appears in the lithological boundary between loess and the Neogene red clay. Loess accumulation in Fengzhou started before 2.48 Ma. The magnetic susceptibility curve indicates 33 cold-dry and humid-warm cycles of paleoclimatic variation in the Qinling Mountains during the last 2.48 Ma. The above climatic fluctuation may be well compared with that of the oxygen isotopic records from deep-sea deposits.     

Discovery of granulite from the Fuping area in southern Qinling Mountains and its geological significance

Two-pyroxene-bearing granulites were discovered for the first time in the Hercynian-Indosinian metamorphic belt of the southern Qinling Mountains. The granulites occur in the lower part of the Fuping complex and are dominated by intermediate-acidic rocks intercalated with a small amount of bands and lenses of basic granulites. The main metamorphic minerals include orthopyroxene, clinopyroxene, biotite, plagioclase and quartz, and orthopyroxenes are often retrogressively transformed into amphiboles. The metamorphic conditions have been estimated to be %T%=720-780℃ and %P%=0.6 GPa. The granulite-bearing Fuping complex probably belongs to early Proterozoic in age. Whether it occurs as the crystalline basement of the southern Qinling Hercynian-Indosinian orogenic belt or as a thrusted slice in the collisional process needs further study.     

北秦岭松树沟接触变质岩的形成温度研究

本文应用氧同位素和电子探针分析方法测定了北秦岭松树沟阿尔卑斯型超镁铁岩体接触变质带内角闪岩和及其原岩秦岭群斜长角闪片岩的形成温度．角闪岩的角闪石－石榴子石Ｆｅ－Ｍｇ配分温度计给出不同期次形成温度分别是：早期８１５～８５５℃，主期７００～７７０℃．矿物对氧同位素地质测温结果得到，角闪岩的主期变质温度为７４５～７７０℃，与其电子探针结果在误差范围内一致；斜长角闪片岩为５００～６０５℃，代表了秦岭群区域变质温度     

佛坪地区印支期花岗岩的成因

通过地质、岩石学及地球化学研究,认为秦岭造山带佛坪地区印支期花岗岩是基性岩浆和酸性岩浆混合的产物,属岩浆混合型(H型)花岗岩;佛坪地区在秦岭主造山过程中曾发生强烈的壳慢相互作用,是一个深层岩浆活动中心。     

基于变形分解与斜向汇聚理论的秦岭--大别造山带构造变形研究

板块汇聚碰撞过程中,常常造成应力矢量与板块边缘的非直交关系,导致平移分量和缩短分量的产生,它们并非不同时期、不同应力场的产物;这种斜向汇聚产生大陆造山带的不对称扇型结构及花状构造,也可能是大陆增生保存的重要形式之一;变形分解作用使得岩石在变形过程中产生纯剪变形分量和单剪变形分量,且不受尺度控制;该理论常被应用于解释造山带尺度的许多构造问题,在秦岭造山带中进行变形分解和板块斜向汇聚研究,有望在理论上有所突破.     

北秦岭罗汉寺岩群锆石年龄及地质意义

目的准确测定北秦岭罗汉寺岩群辉长岩脉的形成时代,探讨其地质意义。方法采用激光剥蚀等离子质谱法,对辉长岩中锆石进行U-Pb同位素定年。结果辉长岩形成年龄为475 Ma±4 Ma。结论罗汉寺辉长岩脉的形成时代与北秦岭两条高压—超高压变质带和富水杂岩成岩时代接近或一致,它的形成很可能与北秦岭早古生代岛弧体系碰撞有关。     

秦岭新生代构造隆升研究

通过构造隆长的性质及方式、夷平面的演变、沉积响应、隆升的幅度和速率、水系结构以及河流阶地，对秦岭造山带新生代构造隆升的研究成果作了系统的总结研究，并提出了加强对渭河盆地的形成演化研究是解决秦岭新生代构造隆升历史问题的关键。     

秦岭植物资源利用和可持续发展研究

分析了秦岭植物资源的利用和可持续发展在西部大开发中的重要地位和作用，对秦岭植物资源的现状、保护、利用和如何进行可持续发展作了分析研究。总结出合理发展旅游业，利用森林草场资源，保护经济植物及发展优势植物的培育是秦岭植物资源利用和可持续发展的有效途径。     

秦岭二台子金矿床地质地球化学再研究

为了指导找矿，通过近年来找矿预测获得的新突破和积累的较新测试资料，对二台子金矿床作出进一步的认识和总结，在探讨矿床成矿大地构造背景的基础上，提出矿床所在盆地的容矿岩系发育模式，在矿床成矿作用演化研究中，进一步阐述了矿床形成经历的同生与后生两次成矿作用，分别与秦岭造山带南北陆块俯冲碰撞造山导致被动大陆一侧局部出现伸展断陷式盆地和转入陆内逆冲推覆造山的构造－岩浆活动密切耦合。     

渭河北迁与秦岭抬升

在测定陕西咸阳附近渭河 级阶地沉积剖面不同层位的年龄并推算出各主要层段的沉积速率后,表明自下而上沉积速率有逐渐增大的趋势,尤其是全新世阶段的更为明显,沉积速率变化趋势与秦岭及青藏高原隆升过程有准同步规律。结合在秦岭北侧观察到的具体沉积物北推的现象和全新世后期又恰是渭河北迁距离最大的事实,提出了渭河北迁的根本原因是秦岭的抬升。