Sm—Nd and Zircon U—Pb Isotopic Constraints on the Age of Formation of the Precambrian Crust in Southeast China

Nd model ages(TDM) of the Pre-Mesozoic crustal rock samples from Southeast China range from 1.2 to 3.5Ga.Two age peaks of 1.4Ga and 1.8 Ga are observed in the histogram of TDM model ages.Available U-Pb zircon inheritance ages are concentrated around 1.2-1.4Ga,1.8Ga and 2.5Ga,respectively.The combined use of Sm-Nd and U-Pb zircon inheritance ages suggests that the formation of the Precambrian curst is of episodic character.The oldest crustal nucleus may have been formed during the Late Archean(2.5Ga or older?).A rapid production of the crust took place 1.8 Ga ago,consistent with the global crust formation event at 1.7-1.9Ga.Another important episode of the addition of juvenile crustal material from the mantle in Southeast China took place 1.2-1.4Ga ago,during which the pre-existing crust was strongly reworked and/or remelted.     

用自然正交分解方法预报冬小麦产量

按自然正交分解方法，把小麦气象产量分解成正交的空间场和时间场，进而作出区域内各点（县）产量预报，避免了抽样选点和分居的人为性，提出大范围粮食产量预报方法。     

水洞岭地段应用铅同位素方法找矿评价的研究

应用铅同位素方法，对水洞岭和桑树坪区段的铅同位素特征与桐柏大河铜锌矿床进行对比，认为水洞岭地段寻找优地槽块状硫化物层控型矿床有利，深部找铜矿有一定希望。     

The Coupled Re—Os and Pt—Os Systematics：A Theoretical Consideration

The ^190Pt-^186Os system should be a unique tracer for mantle processes be-cause both Pt and Os are concentrated in the mantle.The ^190Pt-^186Os system will also be a good supplement to the ^187Re-^187Os system for dating and tracing mantle pro-cesses because the ^190Pt-^186Os system is not so easily contaminated by crustal materials as the ^187Re-^187Os system.In turn,the application of the ^187Re-^187Os system to Pt-enriched materials uncontaminated by crustal materials will indirectly refine the half life of ^190Pt.The ^190Pt is refined.In the coupled ^187Re-^187Os and ^190Pt-^186Os sys-tematics,an ^186Os*/^190Pt-^187Os*/^187Re Concordia diagram similar to the ^206Pb*/^238U-^208Pb*/^232Th Concordia can be constructed.In such a Concordia diagram,a date will be obtained so long as the ^190Pt-^186Os system remains closed even if the ^187Re-^187Os sys -tem is contaminated by crustal materials.In addition ,for the coupled ^190Pt-^186Os and ^187Re-^187Os systematics,the mantle processes and the interactions between the mantle and the crust will be described by two ratios:^186Os/^188Os and ^187Os/^188Os .The coupled ^187Re-^187Os and ^190Pt-^186Os systematics will be a powerful tool in the investigation of the geodynamic history of the Earth because the ^187Re-^187Os system is sensitive to the interactions between the mantle and the crust,while the ^190Pt-^186Os system is a good tracer for mantle processes.     

齐大山铁矿黑云变粒岩单锆石年龄及意义

齐大山特大型鞍山式铁矿的成矿时代，以往都是根据铁矿的构造和建造特征，以及与铁矿伴生的花岗岩类岩体的同位素年龄数据间接推断的。本文最近获得了该铁矿的黑云变粒岩中，单颗粒锆石Ｕ－Ｐｂ同位素年龄为（２５３３±５３）×１０￣６ａ。这是迄今为止研究该矿床成矿时代较为可靠的直接测年数据。     

自然水中的稀土元素及其表生过程

自然水中的稀土元素及其表生过程王仲武（中国科学院地球化学研究所，贵阳５５０００２）关键词稀土元素，自然水体，地球化学行为利用稀土元素在不同岩石中的含量和配分模型，可以探讨地质过程和物质来源。同时，不’．伺的麦生水源具有不同酸碱度和含有不同的离于及有机...     

祁雨沟金矿自然金的标型特征及其找矿意义

本文以２８００粒自然金的研究为基础，系统讨论了自然金的标型特征。研究指出：本矿床应具较大规模，矿区内除Ｊ＿２、Ｊ＿４角砾岩体外，其余几个角砾岩体也应有一定远景，｛１１１｝、｛１１１｝＋｛１００｝、｛１１０｝的出现可指示富矿地段，自然金晶体形态的空间分带规律可确定（岩）矿体的剥蚀深度及评价外围角砾岩体的含矿性及远景；自然金中Ｂｉ可做为找矿评价的指示元素。