藏南拿日雍错片麻岩穹窿中新世淡色花岗岩的形成过程:变泥质岩部分熔融与分离结晶作用

拿日雍错片麻岩穹窿位于特提斯喜马拉雅带的东部,穹窿边部淡色花岗岩脉形成于21.8±0.3Ma,穹窿核部主体淡色花岗岩的结晶年龄为20.1±0.1Ma,其中1件样品记录了~17.3Ma热液蚀变事件。大部分淡色花岗岩具有以下特征:(1)较高的Si O2(72.9%),Al2O3(14.7%)和A/CNK(1.1),较低的Fe O、Mg O、Mn O和Ti O2;(2)高度变化的大离子亲石元素(如Rb、Sr、Ba)和高场强元素(如Nb、Ta、Hf、Th)和Rb/Sr、Nb/Ta、Zr/Hf比值;(3)富集轻稀土元素,亏损重稀土元素,Eu和Nd都显示负异常(Eu/Eu*0.7,Nd/Nd*=0.5~0.8);(4)Sr同位素比值变化范围较大(87Sr/86Sr(t)=0.7132~0.7330),但Nd同位素比值一致(εNd(t)=-12.4~-10.9)。这些特征表明:拿日雍错淡色花岗岩形成于20Ma,是变泥质岩部分熔融作用的产物,经历了不同程度的斜长石、锆石、独居石、磷灰石、富Ti矿物等的分离结晶作用。     

藏南定结地区早中新世淡色花岗岩的形成机制及其构造动力学意义

定结日玛那穹窿位于高喜马拉雅带中段,由花岗片麻岩、变泥质岩、变基性岩及大量淡色花岗岩等组成,经历了角闪岩-麻粒岩相变质作用。为厘定淡色花岗岩的形成机制以及与高级变质岩的关系,我们对淡色花岗岩和高级变质岩进行了全岩元素和Sr和Nd同位素组成和SHRIMP锆石U-Pb地质年代学测试。全岩元素和Sr-Nd同位素测试结果揭示淡色花岗岩具有以下特征:(1)高SiO₂ (>72%),高Al₂O₃ (>12%)和高A/CNK比值 (>1.0);(2)高Rb,低Sr,高Rb/Sr比值(>1.0);(3)高∑REE和明显的负Eu异常;(4)高Sr同位素初始比值(0.7621~0.8846)和低ε_Nd(t)值(-13.0~-20.2)。淡色花岗岩的高Rb/Sr比值和Sr-Nd同位素系统特征表明其形成机制为主要为白云母脱水部分熔融作用,源区为由花岗片麻岩和变泥质岩组成的混合源区。SHRIMP锆石U-Pb年代学研究揭示出定结地区淡色花岗岩具有21.0±0.7Ma和15.8±0.1Ma 2期年龄,花岗片麻岩的锆石变质增生边年龄为22.2±1.4Ma,与该区的榴辉岩退变质年龄一致。这些数据共同表明,花岗片麻岩和 变泥质岩在22~21Ma发生高级变质和深熔作用,形成早期淡色花岗岩岩浆,在~16Ma进一步深熔,形成晚期淡色花岗岩岩浆。     

赣东南富城杂岩体的地球化学和年代学研究

富城杂岩体出露于赣东南,与闽西南的红山岩体共同构成富城-红山花岗质杂岩。富城杂岩主要由富城黑云母巨斑粗粒二长花岗岩、粗石坝中粒二云母花岗岩和珠长洞含红柱石细粒花岗岩三个单元组成。富城花岗岩含较低的 SiO_2、Rb、Nb 和较高的 Al_2O_3、Ba、Sr、Zr、REE 含量,岩石的 ACNK>1.10,K_2O/Na_2O>1.60。粗石坝花岗岩以高 SiO_2、K_2O,低 CaO、P_2O_5和富 Al(ACNK=1.13～1.20)为特征;岩石含较高的 Rb、Nb 和低的 Ba、Sr、Zr、REE 含量,并具有相对低的 K/Rb 和δ(Eu)比值。珠长洞含红柱石花岗岩的地球化学特征相似于富城花岗岩,除了更高的 ACNK 值(1.22～1.36)和 Rb、Nb 含量以及稍低的 Sr、Ba、Zr、REE 含量。富城单元的~(84)Sr/~(86)Sr 初始比值是0.7135～0.7196,ε_(Nd)(t)是-9.4～-10.2,Nd 模式年龄是1.78Ga 到1.84Ga,其中的锆石 Hf 模式年龄是1.70～1.89Ga,与 Nd 同位素一致;粗石坝单元具有与之相似的 Nd-Hf 同位素组成;珠长洞单元的~(87)Sr/~(86)Sr 初始比值更高(0.7214),ε_(Nd)(t)更低(-16.9),而 Nd 模式年龄达2.37Ga。这些地球化学特征表明富城杂岩体的源岩都是由古老物质组成的沉积岩,其中富城和粗石坝单元起源于具晚古元古代模式年龄的基底,而珠长洞单元的源区物质具有早古元古代平均地壳存留年龄。富城杂岩体的各单元之间没有显示一致的变化规律,表明它们不是单一岩浆演化的结果,它们成分的差异主要受源区成分影响。LA-ICPMS 的锆石 U-Pb 定年显示富城黑云母花岗岩形成较早(239±17Ma),而粗石坝和珠长洞花岗岩形成稍晚(231±16 Ma 和229±6.8 Ma)。它们的形成时代与华南印支期早期构造-岩浆活动的峰期一致。结合地球化学和岩石组合特征,可以认为富城-红山杂岩形成于同构造背景。     

北大别早白垩纪花岗岩类的Sm-Nd和锆石Hf同位素及其构造意义

大别造山带产出两期早白垩纪造山后花岗岩类:早期(≈132Ma)变形的角闪石英二长岩和斑状二长花岗岩具高钾的类埃达克岩的地球化学特征,形成于增厚地壳(>50km)的下地壳部分熔融;晚期(≈128Ma)未变形的花岗岩包括细粒二长花岗岩和钾长花岗(斑)岩,属于正常安山岩-英安岩-流纹岩系列岩石,它们形成于相对薄的地壳(<35km)的下地壳部分熔融。早期变形的花岗岩类中,角闪石英二长岩的(~(87)Sr/~(86)Sr)_i=0.7066～0.7076,ε_(Nd)(t)=-20.3～-27.8,类似于扬子下地壳基性麻粒岩的Sr-Nd同位素特征,其中白垩纪岩浆锆石(≈132Ma)Hf同位素初始比值(ε_(Hf)(t))和两阶段Hf模式年龄(t_(DM2))分别为-29.30.5和303065Ma;我们认为角闪石英二长岩源于锆石Hf模式年龄约3.0Ga的基性下地壳部分熔融。早期斑状二长花岗岩的(~(87)Sr/~(86)Sr)_i=0.7078～0.7083,ε_(Nd)(t)=-15.8～-20.0,类似于北大别英云闪长质-花岗质片麻岩的Sr-Nd同位素特征,其白垩纪岩浆锆石(≈132Ma)的ε_(Hf)(t)和t_(DM2)分别为-24.80.5和274434Ma。我们认为宽状二长花岗岩源于约2.7Ga的中酸性下地壳部分熔融。晚期未变形的花岗岩的(~(87)Sr/~(86)Sr)_i=0.7069～0.7105,ε_(Nd)(t)=-16.4～-22.1,类似于北大别英云闪长质-花岗质片麻岩的Sr-Nd同位素特征;其白垩纪岩浆锆石(≈128Ma)的ε_(Hf)(t)具有较大的变化范围(-25.2～7.4),主要峰值为-22.5±0.5,次要峰值为-16.3±0.7,并有少量正的ε_(Hf)(t)值5.8～7.4,与ε_(Hf)(t)值对应的t_(DM2)分别为2600±40Ma、2211±68Ma和743±130Ma。我们认为晚期未变形的花岗岩源于锆石Hf模式年龄约2.6～2.2Ga的中酸性下地壳部分熔融,源区夹杂新元古代新生的陆壳。在大别造山带垮塌之前(>132Ma),增厚地壳(>50km)的下地壳存在双层结构:锆石Hf模式年龄约为3.0Ga的基性下地壳基底和约2.7Ga的中酸性(英云闪长质-花岗质)上部下地壳.在大别造山带伸展垮塌的晚期阶段(≈128Ma),减薄的下地壳(<35km)主要为锆石Hf模式年龄约2.6～2.2Ga的中酸性(英云闪长质-花岗质)岩石,并夹杂少量新元古代Rodinia超大陆裂解时形成的新生陆壳。     

华北陆块北缘崇礼-赤城地区晚古生代花岗岩类的锆石年龄和Sr-Nd-Hf同位素组成

本文报道冀北崇礼-赤城地区晚古生代花岗岩类岩石的锆石U-Pb年龄和Sr-Nd-Hf同位素组成特征.它们出露在华北陆块北缘的构造单元内,侵位于中高级变质基底岩石红旗营子群中.锆石LA-ICP-MS定年结果表明,海流图花岗岩岩体记录了两期岩浆作用,即299±3Ma和254±11Ma;镇宁堡片麻状二长花岗岩和白花沟片麻状黑云母石英二长闪长岩分别形成于287±1Ma和252±3Ma.这些晚古生代花岗岩类岩石具有较低的初始~(87)Sr/~(86)Sr值(0.7062～0.7076)、低的ε_(Nd)(t)值(-18.1至-9.6)和古老的Nd亏损地幔模式年龄(2.49～1.87Ga).其锆石的ε~(Hf)(t)值变化在-13.2至-7.4之间,Hf平均地壳模式年龄值(T_(DM)~C)在2.15Ga至1.79Ga之间.锆石Hf同位素特征与全岩Nd同位素特征指示古老的华北陆块地壳物质是花岗岩浆的主要物源.在形成时代和地球化学特征上,崇礼-赤城地区晚古生代花岗岩与出露在东部丰宁-承德地区的花岗岩类岩石既有相似性,又有不同之处,可能代表华北陆块北缘不同构造背景下岩浆作用的产物.     

藏南错那地区空布岗中新世淡色花岗岩的成因机制

空布岗位于特提斯喜马拉雅带东部、桑日-错那裂谷系内，发育二云母花岗岩、白云母淡色花岗岩、含石榴子石淡色花岗岩以及混合岩淡色体。LA-MC-ICP-MS锆石U-Pb定年显示，空布岗白云母淡色花岗岩结晶年龄为16.9±0.1Ma。全岩元素地球化学分析表明：二云母花岗岩为过铝质富钠花岗岩，具有较高的Sr (107×10^-6～141×10^-6)和Ba (230×10^-6～311×10^-6),较低的Rb(108×10^-6～221×10^-6)和Rb/Sr比值(0.78～2.07),Ba与Rb/Sr比值没有相关性，指示其为白云母含水部分熔融作用的产物。白云母淡色花岗岩为过铝质富钾花岗岩，具有较高的Rb(>270×10^-6)和Rb/Sr比值(5.2～9.5),但是其Sr(<58.5×10^-6)和Ba(<167×10^-6)含量较低，Ba与Rb/Sr比值呈现明显的负相关关系，表明它是白云母脱水...     

壳幔作用导致武平花岗岩形成——Sr-Nd-Hf-U-Pb同位素证据

岩石学、元素地球化学和Sr-Nd-Hf-U-Pb同位素的综合研究显示,武平花岗质杂岩体是由形成时代和成因不同的黑云母花岗岩和含石榴子石花岗岩组成。LA-ICPMS锆石U-Pb定年指示前者形成于161．4 Ma,后者形成于113 Ma。黑云母花岗岩以中等富集大多数不相容元素和中等轻重稀土分异为特征,岩石具有低的87Sr／86Sr初始比值(<0．710)和高的εNd(t) 值(-2．6--5．7)。结合与附近基底变质岩的同位素对比,论文指出黑云母花岗岩岩浆是由元古代基底变质岩部分熔融产生的熔体与幔源岩浆的强烈混合形成。不均匀的锆石Hf同位素组成(εHf(t)=-3．6--10．8)支持了这种混合成因模式。含石榴子石花岗岩以富Si、Al、Na、K、Nb、Ta、Y和HREE而贫P、Sr、Ba、LREE、Zr和Hf含量为特征,它们具有低的(La/Yb)n, Zr／Hf、Nb／Ta比值和高的Rb／Sr比值,显示了强烈的以斜长石为主的分异特征;它们的87Sr／86Sr初始比值大于0．710,εNd(t) =-7．1,锆石的Hf同位素较低且相对均匀(εHf(t)平均值为-9．7),表明岩浆没有受到明显的地幔组分混染。结合它们高的HREE含量,论文指出它们的母岩浆很可能是由早期熔融事件的富石榴子石残留相再次熔融形成。因此,南岭地区中生代花岗岩的地球化学差异很可能反映了岩浆形成过程中壳幔作用的强弱。     

下扬子地区姚村A型花岗岩年代学、地球化学特征及岩石成因

姚村岩体位于下扬子江南造山带东北端,主要由中心相的中粗粒正长花岗岩和边缘相的细粒似斑状正长花岗岩组成。本文对该岩体进行了详细的锆石U-Pb年代学、主量元素、微量元素以及Nd-Hf同位素研究。LA-ICPMS锆石U-Pb定年表明姚村岩体的形成年龄为(127.6±1.4)Ma,为燕山晚期岩浆活动的产物。岩石地球化学研究表明姚村岩体属于A型花岗岩,具高硅、富铁,锆饱和温度高、轻重稀土分馏明显、富集Rb、Th、U、K、Pb等元素而亏损Ba、Nb、Sr和Ti等元素、铕负异常显著(Eu/Eu*=0.22～0.46)的特点。姚村岩体的全岩εNd(t)值与锆石εHf(t)值分别变化于-6.2～-5.7和-13.9～-5.0,两阶段Nd和Hf同位素模式年龄分别为T_(DM2)(Nd)=1439～1532 Ma和T_(DM2)(Hf)=1508～2062 Ma,Nd同位素的模式年龄重叠于Hf同位素模式年龄。结合区域地质研究成果认为,姚村岩体可能于早白垩世古太平洋板块俯冲作用之后伸展-拉伸环境下,由中元古代地壳重熔而成。     

江西云山岩体的成因：年代学、地球化学及Nd- Hf同位素制约

云山岩体位于赣北的江南造山带东段九岭隆起带东北端,主要由二云母二长花岗岩组成。本文对该岩体进行了详细的锆石U-Pb年代学、主量元素、微量元素以及Nd-Hf同位素研究。LA-ICP-MS锆石U-Pb定年表明云山二云母二长花岗岩的形成年龄为125.6±1.1Ma,为燕山晚期早阶段岩浆活动的产物。岩相学和岩石地球化学研究表明云山岩体属于高分异的S型花岗岩,具高硅、富碱、过铝质,锆饱和温度低、轻重稀土分馏明显、富集Rb、Th、U、K、Pb等元素而亏损Ba、Nb、Sr和Ti等元素、铕负异常显著(Eu/Eu~*=0.13～0.20)的特点。云山岩体的全岩ε_(Nd)(t)值与锆石ε_(Hf)(t)值分别变化于-3.9～-5.1和-1.0～-8.8,两阶段Nd和Hf同位素模式年龄分别为T_(DM2)(Nd)=1.35～1.44 Ga和T_(DM2)(Hf)=1.25～1.75 Ga,Nd同位素的模式年龄重叠于Hf同位素模式年龄。结合其CaO/Na_2O值均小于0.3,本次研究认为云山岩体的源区很可能是来自于双桥山群中的富泥质变质沉积岩及少量火成岩,形成于早白垩世古太平洋板块俯冲之后的弧后伸展的构造环境。     

藏南也拉香波早渐新世富钠过铝质淡色花岗岩的成因机制及其构造动力学意义

藏南也拉香波穹隆位于近东西向展布的北喜马拉雅片麻岩穹隆(NHGD)最东端,主要由石榴角闪岩、石榴石云母片麻岩、二云母花岗岩和淡色花岗岩组成.SHRIMP锆石U/Pb定年结果表明也拉淡色花岗岩的结晶年龄为35.3±1.1Ma,明显老于位于该穹隆以西类似的淡色花岗岩(年龄普遍<25Ma).全岩元素和Sr-Nd同位素测试结果揭示：(1)也拉香波淡色花岗岩为过铝质富钠花岗岩;(2)与片麻岩相似,也拉香波淡色花岗岩富集大离子亲石元素(LILE,如K,Sr,Rb和Ba),但亏损Ti,Y,Yb,Sc和Cr;(3)和片麻岩或角闪岩相比,也拉香波淡色花岗岩同时亏损LREE和HREE,但与HREE相比,LREE相对富集;(4)在Sr-Nd同位素系统特征上.淡色花岗岩初始Sr同位素比值与角闪岩的相当,在0.711949～0.719344之间;但远小于片麻岩.而Nd同位素组成在片麻岩和角闪岩之间,在-8.9～-15.0之间.以石榴角闪岩和片麻岩为端元,简单混合计算表明：由石榴角闪岩为主和片麻岩为辅组成的混合源区发生部分熔融作用,各自产生的熔体进行不同程度的混合,可形成类似于也拉香波淡色花岗岩成分的岩浆,其中角闪岩的部分熔融起主要作用.使用Zr在岩浆中的饱和浓度温度计得出岩浆的平均温度为673℃,在此温度下,变泥质片麻岩在高压(～10kbar)条件下的水致部分熔融和角闪岩部分熔融都可形成也拉过铝质富钠淡色花岗岩,但角闪岩的脱水部分熔融起主导作用.在地壳增厚条件下,下地壳角闪岩的部分熔融可能是导致喜玛拉雅造山带从缩短增厚向伸展垮塌转换的主要因素之一.     

摩擦桩基桩土间极限摩阻力取值问题探讨

通过对广珠东线高速公路横沥大桥的试桩及土体的工程地质条件分析,总结出影响摩擦桩基桩土间极限摩阻力取值的一般问题以及解决问题的方法和措施。     

从榴辉岩与围岩的关系论苏鲁榴辉岩的形成与折返

位于华北和扬子两板块碰撞带中的苏鲁榴辉岩形成的温压条件不但是超高压，而且是高温。榴辉岩的PTt轨迹表明其为陆-陆磁撞俯冲带的产物。榴辉岩的区域性围岩花岗质片麻岩为新元古代同碰撞期花岗岩，榴辉岩及其他直接围岩皆呈包体存在于其中，并见新元古代花岗岩呈脉状侵入榴辉岩包体中。区域性围岩新元古代花岗岩的锆石中发现有柯石英、绿辉石等包裹体，表明新元古代花岗岩的组成物质也经受过超高压变质作用，且榴辉岩与围岩新元古代花岗岩的锆石U-Pb体系同位素年龄基本相同。但新元古代花岗岩所记录的变质作用和变形作用期次（或阶段）却少于榴辉岩。椐上述可得如下推断：超高压榴辉岩与新元古代花岗岩岩浆是同时在碰撞带底部（俯冲板块前部）形成的；榴辉岩的第一折返阶段是由新元古代花岗岩岩浆携带上升的，其第二折返阶段是和新元古代花岗岩一起由逆冲及区域性隆起而上升，遭受剥蚀。     

The Importance of the Precipitation and the Susceptibility of the Slopes for the Triggering of Landslides Along the Roads

In order to characterise the influence of the heavyrains on the observed landslides during the 1996–1997hydrological cycle, rainfall records for the last 100years are analysed from 104 stations in easternAndalusia. Regarding the amounts of rain recordedbetween October 1996 and March 1997 in the 104stations studied, 31 presented new all-time records;15 presented values that were 80–100% of thepre-1995 record; 49 stations, 80–50%; and 9stations, < 50%. A map has been devised of thesusceptibility of the materials through which thesouth-eastern Andalusian road network crosses,together with an inventory of the damage caused byinstability phenomena on banks and cuttings of theroad network during the winter of 1996–1997. Therelationships between the rainfall during the studyperiod, the damage caused to the road network and thesusceptibility of the materials affected are analysed.The results indicate that there is a clearcorrespondence between the rainfall recorded and thesusceptibility of the materials with the inventorieddamage. It is concluded that the widespread seriousdamage caused in early 1997 to the roads andsurrounding areas in the Alpujarra region and thecoast of the Province of Granada was mainly caused bythe extraordinarily heavy rains. However, considerablyless damage was observed where the susceptibility ofthe terrain is low, thus highlighting the extremeusefulness of terrain-susceptibility maps for riskprevention and territorial planning.     

某高速公路下伏煤矿采空区稳定性分析

在论述某高速公路下伏砦脖煤矿采空区地质、采矿和工程地质特征的基础上, 进行了稳定性数值模拟分析, 定性与定量地分析与评价了该煤矿采空区的地表变形特征及稳定性。研究结果表明: 该煤矿采空区的变形尚未完成, 对拟建的高速公路将产生很大的危害, 必须采取相应的工程治理措施。      

混凝剂处理钻井废泥浆液的研究

通过烧杯搅拌实验对混凝剂处理钻井废泥浆液进行研究,从混凝剂适应p H值范围、混凝效果、沉降速度三方面研究比较,找出一种较为理想的混凝剂,并分析了影响混凝剂性能的主要因素,确定了混凝剂的最佳投放剂量。      

黄河源区水环境变化及黄河出现冬季断流的原因

自1954年有水文观测资料以来，黄河曾在青海省玛多县黄河沿水文站发生过3次断流。本文在分析黄河源区水环境特征及其影响因素的基础上指出，鄂陵湖、扎陵湖的环湖融区调节能力低，当遇到连续干旱、冬季其调节水量不足以维系黄河径流时便会发生断流，这是断流的主因。湖水位降低、开采沙金、过度放牧等自然和人为因素也会对黄河发生断流产生影响。鄂陵湖口附近黄河上修建的水电站开始蓄水，提高了两湖及环湖融区的调节能力，今后黄河冬季出现断流的可能性将大为降低。     

Unity of the national and the international in the socio-cultural development of the peoples of the USSR

International unity is becoming ever stronger in this country owing to an increasing similarity in the development of the cultural environment. This comprises the provision of all the country's republics with a sufficient number of schools, theatres, and other institutions and cultural information media in accordance with the needs of the population. An important part is played by the rise in ‘the general educational level, as well as the level of professional qualifications and skills. Among all the Soviet nations and nationalities, this rise being more rapid among formerly backward peoples. Prominent among the factors of internationalization is the progressive development of the nationalities’ cultural resources, while professional culture is being increasingly brought within the reach of the masses.The implementation of the nationalities policy promotes the all-round development of all Soviet nations and nationalities, their drawing together, the upsurge of the individual capabilities of every Soviet citizen.     

Artemia in the Salt Lakes of Russia:the Productivity of Populations,the Reserves of the Cysts and the Fisheries

正Artemia cysts are an extremely important component of aquaculture diets.It is well established that the cultivation of fish and shellfish derive substantial health and growth advantages when Artemia are included in the diets of the     

天山南坡科其喀尔冰川表碛区小气候特征研究

利用天山南坡科其喀尔冰川3号观测站2009年全年的气象观测资料,分析研究了科其喀尔冰川表碛区的小气候特征. 结果表明：总辐射和净辐射夏秋季较高、冬春季较低;反射辐射和地表反照率反之. 与其他地区不同,该区主要受积雪物理性质和下垫面状况的影响,冬春季地表反照率日变化表现为由大到小的变化过程,夏秋季表现为倒U型. 温度年变化表现为夏秋季高、冬春季低,最高月均值出现在8月,为9.4℃,最低月均值出现在1月,为-9.6℃. 受山谷风和冰川风的影响,全年的风向以西北风和西北偏西风为主,风向的日变化以11：00为界发生转向. 受降水和冰川消融等的影响,比湿夏秋季月均值较大,冬春季月均值较小.     

Climate: Is the past the key to the future?

 The climate of the Holocene is not well suited to be the baseline for the climate of the planet. It is an interglacial, a state typical of only 10% of the past few million years. It is a time of relative sea-level stability after a rapid 130-m rise from the lowstand during the last glacial maximum. Physical geologic processes are operating at unusual rates and much of the geochemical system is not in a steady state. During most of the Phanerozoic there have been no continental ice sheets on the earth, and the planet’s meridional temperature gradient has been much less than it is presently. Major factors influencing climate are insolation, greenhouse gases, paleogeography, and vegetation; the first two are discussed in this paper. Changes in the earth’s orbital parameters affect the amount of radiation received from the sun at different latitudes over the course of the year. During the last climate cycle, the waxing and waning of the northern hemisphere continental ice sheets closely followed the changes in summer insolation at the latitude of the northern hemisphere polar circle. The overall intensity of insolation in the northern hemisphere is governed by the precession of the earth’s axis of rotation, and the precession and ellipticity of the earth’s orbit. At the polar circle a meridional minimum of summer insolation becomes alternately more and less pronounced as the obliquity of the earth’s axis of rotation changes. Feedback processes amplify the insolation signal. Greenhouse gases (H₂O, CO₂, CH₄, CFCs) modulate the insolation-driven climate. The atmospheric content of CO₂ during the last glacial maximum was approximately 30% less than during the present interglacial. A variety of possible causes for this change have been postulated. The present burning of fossil fuels, deforestation, and cement manufacture since the beginning of the industrial revolution have added CO₂ to the atmosphere when its content due to glacial-interglacial variation was already at a maximum. Anthropogenic activity has increased the CO₂ content of the atmosphere to 130% of its previous Holocene level, probably higher than at any time during the past few million years. During the Late Cretaceous the atmospheric CO₂ content was probably about four times that of the present, the level to which it may rise at the end of the next century. The results of a Campanian (80 Ma) climate simulation suggest that the positive feedback between CO₂ and another important greenhouse gas, H₂O, raised the earth’s temperature to a level where latent heat transport became much more significant than it is presently, and operated efficiently at all latitudes. Atmospheric high- and low-pressure systems were as much the result of variations in the vapor content of the air as of temperature differences. In our present state of knowledge, future climate change is unpredictable because by adding CO₂ to the atmosphere we are forcing the climate toward a “greenhouse” mode when it is accustomed to moving between the glacial–interglacial “icehouse” states that reflect the waxing and waning of ice sheets. At the same time we are replacing freely transpiring C3 plants with water-conserving C4 plants, producing a global vegetation complex that has no past analog. The past climates of the earth cannot be used as a direct guide to what may occur in the future. To understand what may happen in the future we must learn about the first principles of physics and chemistry related to the earth’s system. The fundamental mechanisms of the climate system are best explored in simulations of the earth’s ancient extreme climates. Received: 7 November 1996/Accepted: 23 January 1997