大三啦-大地构造

大地构造学（Tectonics）4.

Plate

tectonics:

A

UnifyingTheoryA

unifying

theory

is

one

that

helpsexplain

abroad

range

of

diverse

observationsinterpret

many

aspects

of

a

science

on

a

grand

scaleand

relate

many

seemingly

unrelated

phenomenaPlate

tectonics

is

a

unifying

theory

for

geology.(1)

A

Unifying

TheoryPlate

tectonics

helps

to

explainearthquakesvolcanic

eruptionsformation

ofmountainslocation

ofcontinentslocation

of

oceanbasinsTectonic

interactionsaffectatmospheric

and

oceaniccirculation

and

climategeographic

distribution,evolution

and

extinctionof

organismsdistribution

andformation

of

resourcesPlate

tectonics

is

a

unifying

theory

for

geology1912年魏格纳

大陆漂移说，后经E.Argand(1924)、A.Holmes(1928)、OuToit(1937)等进一步发挥，然而最终未能成为大地构造学派的主流思想。The

continental

drift

theory

wasgenerally

accepted

ingeosciencesonly

during

the

second

half

of

the20th

century,

after

the

hypothesesof

Alfred

Wegener

had

beensupported

through

the

discovery

ofa

mechanism

for

continental

drift,and

an

adequate

energy

source,

inthe

convection

currents

of

theplastic,

very

weak

upper

mantle,

orasthenosphere.二十世纪50年代，英国物理学家

M.P.S.Blackeet、S.K.Runcorn通过对大陆古地磁的测量和研究，以精确的数据说明了大陆间的相互位移，促使大陆漂移学说的复兴。板块构造学说的建立是一个复杂、坎坷的历程（1910-1970年)In

1947,Blackett

introduced

a

theory

to

account

for

the

Earth's

magnetic

field

as

a

function

of

itsrotation,

with

the

hope

that

it

would

unify

both

the

electromagnetic

force

and

the

force

of

gravity.

Hespent

a

number

ofyearsdevelo

high-quality

magnetometers

to

test

his

theory,and

eventuallyfound

it

to

be

without

merit.

His

work

on

the

subject,

however,

led

him

into

the

field

of

geophysics,wherehe

eventually

helped

process

data

relating

to

paleomagnetism

and

helped

to

provide

strongevidence

for

continental

drift.In

1965

he

was

invited

to

deliver

the

MacMillan

Memorial

Lecture

to

the

Institution

of

Engineers

andShipbuilders

in

Scotland.

He

chose

the

subject

'Continental

Drift‘.Stanley

Keith

Runcorn

(19

November

1922

–

5

December

1995)

was

a

British

physicist

whosepaleomagnetic

reconstruction

of

the

relative

motions

of

Europe

and

America

revived

the

theory

ofcontinental

drift

and

wasa

major

contribution

to

plate

tectonics.地质学家H.H.Hess(1960,1962)提出了海底扩张说，后来得到R.S.Dietz(1961)、F.J.Vine,D.H.Matthews(1963)、J.T.Wilson(1965)、J.R.

Hentzler(1968)等进一步的论证和完善。3. W.J

Morgan、X.Le

Pichon、D.P.

Mekenzie、B.

Isacks等于1968年 地质学会年会上阐述了板块构造学说。K.Condie,

2003Plate

tectonic

theory

is

based

on

the

simple

modelthat:the

lithosphere

isrigidPlate

Tectonics固体地球上层在垂向上可分为性质不同的两个圈层。即上部的刚性岩石圈，下部的软流圈。岩石圈在侧向上被一些构造活动带分割成若干既不连续、又互相“镶嵌”起来的大小不一球面块体，每个块体的厚度相对于其面积及地球半径来说是很薄的，呈板状，故称为岩石圈板块(简称板块)。Plate

TectonicsPlate

tectonic

theory

is

basedon

the

simple

model

that:2.

The

lithospheric

plates

overliehotter

and

weaker

semiplasticasthenosphere,

a

zone

of

partialmelting.坚硬的岩石圈板块驮在塑性的软流圈之上，横跨在地球表面上发生大规模的水平移动。Plate

tectonic

theory

is

based

on

the

simplemodelthat3.

it

consists

of

oceanic

and

continental

crustwith

upper

mantle,

with

plate

regionscontaining

continental

lithosphere

up

to250

km

thick,

and

plate

regions

containingoceani hosphere

up

to

100

km

thickPlate

TectonicsPlate

tectonic

theory

is

based

on

the

simple

modelthat4.

it

consists

of

variable-sized

pieces

called

platesPlate

TectonicsPlate

TectonicsPlate

tectonic

theory

is

based

on

the

simple

model

thatas

plates

move

over

theasthenospherethey

separate,

mostly

at

oceanic

ridges;or

break

into

new

and

smallerplates;在板块分离处，软流圈内的地幔物质上涌，冷凝构造成新的洋壳，使板块新生；Plate

TectonicsPlate

tectonic

theory

is

based

on

the

simple

model

thatas

plates

moveover

the

asthenospherethey

collide

to

form

orogenic

belts

and

amalgmated

into

new

andlarger

plates;in

areas

such

as

oceanic

trenches

where

they

maybe

subducted

backinto

the

mantle;在板块汇聚处，一个板块俯冲到另一个板块之下，使之返回地幔同化，导致板块的消亡。Plate

tectonic

theory

is

based

on

the

simple

model

thatAs

plates

move

over

the

asthenospherethey

form

strike-slip

fault(transform

fault)

across

the

oceanicridges.Plate

TectonicsAfricaNorth

AmericaSouth

AmericaEuropeAtlanticOceanbasinPlate

TectonicsPlate

tectonic

theory

is

based

on

the

simple

model

thatthree

types

of

plate

boundaries

are

zones

of

most

activeon

the

earth’s

surface:volcanoes,

earthquakes,

deformationlocalizatioin…板块的相互运动，激起了和火山活动，推动了大陆漂移和大洋盆地的张开与关闭，也导致了地壳上各种地质构造的产生和各种矿产的形成。Plate

TectonicsPlate

tectonictheory

is

based

on

the

simple

model

thatthree

types

of

plate

boundaries

are

zones

of

most

activeon

the

earth’s

surface:But

the

continental

plates

retain

rocks

with

a

longgeologicalhistory.

较轻的大陆板块，总是驮在软流圈之上漂移，难以消亡掉。因此陆壳上保持有3600Ma以上的地质历史记录。(2)

Types

of

PlatesPlate

or

Lithospheric

plate:

2

types“板块”这一术语，系1965年Wilson在论述转换断层时首先（岩石圈）并不是。整个地球的表壳续完整的圈层，它被首尾相接的活动带（洋中脊、海沟和转换断层）分割成大小不一的块体，叫做岩石圈板块，简称板块。全球的带是板块边界的相对运动造成的，这样全球各带相互交接、首尾相连，它们把岩石圈划分为若干

较弱的板块。1)

Six-plate

subdivisionX.Le

Pichon，1968）以陆壳岩石圈为主体的板块称为陆壳型板块－－欧亚、

、南美、非洲、以洋壳岩石圈为主体的板块称为洋壳型板块－－太平洋、菲律宾海、

－澳大利亚、南极洲、可可、加勒比、纳兹卡Numbers

represent

average

rates

of

relative

movement,

cm/yr2)

Twelve-plate

subdivision

(Mckenzie

et

al.,

1976)PLATE

TECTONICS

—Plate

interiorNot

as

simple

as

it

looks

on

this

map2)

大陆的板块沿大陆 大型板块边界，往往镶嵌着众多的小型板块，如欧亚板块南缘的阿尔卑斯—喜马拉雅活动带，就镶嵌着一系列小板块。在地中海区，加勒比海区同样也存在着一系列小板块。其运动不是由于地幔对流所驱动，而是从属于块的运动而运动。Areasofwide

plate

boundary

deformation岩石圈板块所作大规模的水平运动，是一种在球面上的绕轴旋转运动。可用欧拉定律来描绘。板块沿分离型边界扩张、增生；与此同时它又沿汇聚型边界缩减、消亡，相互补偿，使地球半径保持不变。Plate

Tectonics（3）板块的三联点与运动在板块分布图上，常可见到三条板块边界相交于一点，这个点与三个板块相邻接，叫做板块的三联接合点(或三结点)。任何一对板块间的边界总是以三联接合点作接合点也有可能出现，接合点会立即转化为两个为端点。在理论上，但在一般情况下，

三联接合点。与三联接合点相接的板块边界，可以是分离型、汇聚型或平错型边界。在理论上，这三类边界可以组十六种不同的情况，可以出现十六种不同的三联接合点类型。如以R代表裂谷，T代表海沟，F代表转换断层，则RRR型就是裂谷—裂谷—裂谷型的三联接合点；RTF型代表裂谷—海沟一断层型的三联接合点，其余类推。在

洋中部，洋中脊三条分支的交点是非洲板块、板块和南极洲板块之间的RRR型三联；RRR型分布最广在

洋中部，

洋中脊三条分支的交点是非洲板块、 板块和南极洲板块之间的RRR型三联；非洲东北部的阿法尔三角地区，是红海裂谷、亚丁湾裂谷和东非大裂谷相交接的三联；太平洋东部加拉帕戈斯群岛附近，是太平样板块、可可板块和纳兹卡板块之间的RRR型接合点。非洲东北部的阿法尔三角地区，是红海裂谷、亚丁湾裂谷和东非裂谷相交接的三联；中脊，向东沿亚速尔-直布罗陀一线，主要板块、欧亚板块和非洲板块之间的RRF型接RRF型三联点分布于 洋脊上从亚速尔群岛向北和向南为是平移滑动边界，亚速尔乃是合点。TTT型见于

本州岛东南部海沟、西南

海沟和小笠原海沟在这里相接，成为欧亚板块、菲律宾海板块和太平洋板块之间的三联点。其他接合类型如RTT型、RRT型十分少见。一些三联接合点类型，如RRR型是稳定的，随着板块运动，有保持自己形状的趋势。另有些三联接合点则是不稳定的，随着板块运动，它们很快改变自己的外形。海沟、琉球海沟和小笠原海沟在这里相接，成为欧亚板块、菲律宾海板块和太平洋板块之间的三联点(TTT型)。魏格纳提出，潮汐摩擦力和离极力可作为驱使大陆漂移的原动力。据杰弗利斯计算，地球自转与潮汐引起的作用力都太小，难以驱动大陆漂移。大多数学者相信，板块驱动主导机制应是某种形式的地幔与岩石圈的相互作用。Driving

forces

:

Different

models(3)

Plate

Tectonics-mechanisms1)

Mantle

convectionmodel:

Movement

of

the

platesresults

from

some

type

of

heat-transfer

systemwithin

the

athenosphere.关于地幔对流的规模也有不同的主张。在极块构造学说初创时期，当时认为下地幔的粘度远大于上地幔，那里不可能发生对流，因而主张对流局限于上地幔，即浅对流模式。70年代以来，学者们认识到上、下地幔的粘度相差不大，又主张全地幔对流，即深对流模式。后来发现大洋脊的玄武岩与大洋岛的玄武岩在地球化学上的明显差异，于是浅对流模式又兴起，同时提出上、下地幔的双层对流模式。Moores

and

Twiss,

19952)热柱是由Wilson(1963)在解释火山岛链成因时首先提出来的。Morgan(1971)进一步发展了这一概念。热柱是从核-幔边界升腾而起的一股热流柱体，直径可达几百公里，它可能是由液态外核传递的能量引发的。也有人认为地幔柱是热地幔上升形成的底辟体。类似沉积岩中的盐丘。Hot