Chapter 1 An Introduction to Siliceous Deposits in the Pacific Region

1

CHAPTER 1 AN INTRODUCTION TO SILICEOUS DEPOSITS IN THE PACIFIC REGION

A. IIJIMA, J. R. HEIN, AND R. SIEVER

Though s i l i c a (Si02) has been used f o r c e n t u r i e s f o r many purposes, in recent years s i l i c o n as well as i t s oxide, s i l i c a , a r e becoming widely exploited. For example, s i l i c o n i s used in the semiconductor and coriiputer i n d u s t r i e s ; s i l i c a comprises the f i r e bricks f o r t h e U. S. space s h u t t l e , Columbia, and i s the raw material f o r glass and rilany other products. S i l i c o n and oxygen a r e the two most abundant elements of the e a r t h ' s c r u s t , 2877 and 462, respectively. S i l i c o n i s an iriiportant element of many minerals in rimt igneous, metamorphic, and sedimentary rocks of the e a r t h ' s c r u s t . In sediments and sediirientary rocks, s i l i c a comprises d e t r i t a l grains, s i l i c e o u s organic remains, and authi genic minerals. S i l i c e o u s deposits a r e fine-grained, s i l i c a - r i c h sediments and sedimentary rocks, f o r example c h e r t , s i l i c e o u s shale, diatomite, and so on. Amorphous s i l i c a (opal-A), c r i s t o b a l i t e (opal-CT and opal-C), tridyriiite, chalcedonic quartz, microquartz, and various combinations of these phases a r e the primary minerals of s i l i c e o u s deposits. The source of s i l i c a i s inost coimonly opaline biogenic debris, such as r a d i o l a r i a n s , s i l i c o f l a g e l l a t e s , diatoins, and sponge spicules. The t e s t s and f r u s t u l e s of these marine organisms accumulate in great q u a n t i t i e s over extensive areas of t h e sea f l o o r , e s p e c i a l l y around the polar regions (diatoms) and the equatorial b e l t of high biological productivity ( r a d i o l a r i a n s and diatoms). They a l s o accumulate in other areas where cold, n u t r i e n t rich waters upwell, such as offshore southern C a l i f o r n i a , north Africa, and Peru. These s i l i c a s e c r e t i n g organisms a r e the very basis of the food chain and they are in f a c t t h e cause of a l l the rmjor oceanic f i s h e r i e s world-wide. Phytoplankton, f o r example diatoms, produce much of the atmospheric oxygen. A f t e r hundreds of i e t e r s of burial t h e s i l i c e o u s biogenic debris i s transformed from opaline s i l i c a i n t o c r i s t o b a l i t e , and f i n a l l y i n t o quartz. These mineralogic transformations r e s u l t in t h e recycling of s i l i c a and t r a c e metals and the subsequent formation of s i l i c e o u s shale, porcelanite, and chert. Accompanying the transformation of the s i l i c a t e s t s and f r u s t u l e s i s a l t e r a t i o n of the carbon compounds of the plankton. This material (especially of diatoms) i s the source f o r vast accumulations of natural gas and hydrocarbons. For example, t h e Miocene Monterey and Onnagawa Formations a r e considered t o be t h e source rocks f o r some important petroleum deposits in California and Japan.

2

Siliceous

deposits

are

incorporated

into

oroyenic

belts

by

uplift

of

c o n t i n e n t a l m a r g i n and oceanic c r u s t o r by o b d u c t i o n and t h r u s t f a u l t i n y a t convergent p l a t e niaryins.

Such on l a n d s i l i c e o u s d e p o s i t s a r e found o f e v e r y

aye and a t many l o c a t i o n s i n t h e c i r c u i i i - P a c i f i c

region.

F r a n c i s c a n and Monterey Foriiiations o f C a l i f o r n i a , western

Canada

and Washington,

Onnagaua F o r m a t i o n o f Japan,

t h e Chichibu

Examples i n c l u d e t h e

t h e Cache Creek F o r i i i a t i o n o f and Sanbosan Groups

and t h e

,

t h e Vagoriipolkian S e r i e s o f E a s t e r n U.S.S.R.

Suiiiulony d i a t o i i i i t e o f t h e P h i l i p p i n e s ,

t h e P i s c o F o r m a t i o n o f Peru,

the

arid t h e

Nicoya Complex o f Costa Kica, t o naiiie o n l y a feu.

These s i l i c e o u s d e p o s i t s a r e

cormonly a s s o c i a t e d w i t h uraniuiii, i r o n , manganese,

barium, and phosphate ores.

In

suiluiiary

then,

siliceous

deposits

merit

detailed

study

because:

1)

S i l i c e o u s o r g a n i s m a r e t h e very base o f t h e marine f o o d c h a i n and produce much of

the

atiiiospheric

recycliny

of

oxyyen;

silica

therefore,

understanding

i n t h e marine environment

is

the

distribution 2)

imperative;

and

Siliceous

d e p o s i t s o c c u r i n g r e a t t h i c k n e s s and cover v a s t areas o f t h e sea f l o o r and geosynclinal deposits; occurrence

of

3) S i l i c e o u s d e p o s i t s a r e d i r e c t l y a c c o u n t a b l e f o r t h e

riiany hydrocarbon d e p o s i t s ;

i i i i p o r t a n t d e p o s i t s o f i r o n , manganese,

4)

Siliceous

deposits

occur w i t h

uranium, barium, and phosphate ores.

Because o f t h e b i o l o g i c o r i y i n o f many s i l i c e o u s d e p o s i t s , t h e i r yeocheiiiical transforination formations yeocheniists,

in

the

around

marine

the

environment,

Pacific,

it

and

is

their

essential

occurrence

that

in

many

paleontologists,

and g e o l o g i s t s work t o y e t h e r t o reach a h o l i s t i c u n d e r s t a n d i n y

about t h e o r i y i n and e v o l u t i o n o f these d e p o s i t s . d i s c i p l i n e s needed,

also,

c o o p e r a t e on comparative P r o j e c t 115 was

Not o n l y i s i n t e y r a t i o n o f

workers froiii a l l c o u n t r i e s around t h e P a c i f i c must studies.

W i t h t h e s e riiain p o i n t s i n iiiind I.G.C.P.

The aim o f I.G.C.P.

formed.

P r o j e c t 115 i s t o c o r r e l a t e

sediiiientary processes o f s i l i c e o u s d e p o s i t s i n t h e P a c i f i c b a s i n and i n t h e geosynclinal

areas o f

n e i g h b o r i n y o r o g e n i c b e l t s by means o f s t r a t i g r a p h y ,

p a l e o n t o l o g y , sediriientol ogy, sediiiientary p e t r o l o g y , and geochemistry. The

twenty-five

y e n e r a l overviews, diayenesis

and

southwest Japan.

chapters

i n this

book

are

organized

into

six

groups:

d i s t r i b u t i o n s o f s i l i c e o u s d e p o s i t s , cheiiiical sediinentology,

mineralogy,

diatomaceous

deposits,

and

bedded

cherts

in

Soiiie papers c o u l d e a s i l y be p l a c e d i n inore t h a n one cateyory.

Chapters i! and 3 a r e general overviews.

I n c h a p t e r 2, S i e v e r o u t l i n e s t h e

e v o l u t i o n o f t h e d e p o s i t i o n a l and c l i r l i a t i c environments,

and t h e sources o f

s i l i c a f o r t h e f o r m a t i o n o f c h e r t s as a c o n t i n e n t a l r i f t begins and widens i n t o an open ocean. time-temperature

The d i a g e n e t i c h i s t o r i e s o f t h e c h e r t s can b e s t be viebred i n plots,

subsidence h i s t o r y ,

where

temperature

is

dependent

on

heat

flow

b o t h of which are f u n c t i o n s o f p l a t e t e c t o n i c regimes.

and One

o f t h e iiiost i m p o r t a n t probleiils t o be s o l v e d c o n c e r n i n g t h e f o r m a t i o n o f c h e r t s i n the

Pacific

region

is

brhether o r

not

bedded c h e r t s

i n circuin-Pacific

3

orogenic b e l t s are e q u i v a l e n t t o deep-sea, open-ocean c h e r t s i n t h e P a c i f i c basin. I n Chapter 3 Hein and K a r l show t h a t t h e two groups o f c h e r t s are n o t the same based on l i t h o l o g i c associations,

sedimentation rates,

sedimentation,

sedimentary s t r u c t u r e s ,

Bedded c h e r t s

i n t h e orogenic b e l t s probably formed i n young ocean basins,

block f a u l t e d c o n t i n e n t a l margins,

modes o f formation,

iilechanisriis o f

and geochemistry.

back arc basins, o r adjacent t o i s l a n d arcs.

Chapters 4 through 9 deal w i t h t h e d i s t r i b u t i o n i n space and time o f c h e r t s i n t h e P a c i f i c region. siliceous

rocks

silicastone.

I i j i m a and Utada sumnarize t h e occurrence and o r i g i n o f

in

Japan

and

their

economic

importance

as

sources

T e r t i a r y s i l i c e o u s deposits, s i m i l a r t o t h e Monterey Formation o f

C a l i f o r n i a and composed mostly o f diatoms and t h e i r d i a g e n e t i c products, much o f n o r t h e r n Honshu and Hokkaido. occur

i n several

tectonic

s p i c u l e s and r a d i o l a r i a n s . cherts

formed

under

belts

deep-sea

Mesozoic and Paleozoic bedded c h e r t s

through Japan and are composed mostly o f

oceanic

conditions.

Peninsular Phillipines,

and

of

Koike

review The

The T r i a s s i c conodont-beariny

The d i s t r i b u t i o n o f c h e r t s i n Southeast Asia i s

Paleozoic c h e r t s occur mainly i n Indochina,

Malaysia,

Blocks

Iyo

b i o s t r a t i graphy o f c h e r t s from Japan.

o l d e s t conodont assemblage i s middle Ordovician. c h e r t s are most widespread. o u t l i n e d by Tan.

cover

I i j i m a and Utada f i n d no evidence t h a t these bedded

Paleozoic and Mesozoic conodont

Asia.

of

whereas Tertiary

Mesozoic cherts

and eastern Malaysia.

cherts

are

i n melanges

Thailand,

widespread occur

in

and

i n Southeast Indonesia,

the

Moore shows t h a t c h e r t s i n New Zealand

occur mainly i n the Permian-Jurassic arc-trench-basin

complex o f t h e Rangitata

Oroyen where c h e r t s are associated w i t h submarine volcanic rocks and f l y s c h , and i n t h e Late Cretaceous-Early

Tertiary

mrginal

basins o f western and

n o r t h e r n New Zealand where c h e r t s are associated w i t h s i l i c e o u s shale and limestone.

Widespread r a d i o l a r i a n c h e r t s i n allochthonous accreted t e r r a n e s

throughout t h e C o r d i l l e r a o f western North America,

which range i n age from

Ordovician

by

to

Holdsworth.

Middle

Cretaceous,

are

delineated

Murchey,

Jones,

and

These c h e r t sequences are d i v i d e d i n t o f o u r d i s t i n c t l i t h o l o g i c

associations:

(1) chert-carbonate

chert-argillite

basinal

water facies,

deposits,

deposited on a s u b s i d i n g platform,

(3) interbedded t u f f - c h e r t - a r g i l l i t e

and (4) t u r b i d i t e yraywacke-chert

c o n t i n e n t a l margin.

deposited i n deep water a t a

Gursky and Schmidt-Effing show t h a t t h e mostly Cretaceous

Nicoya Complex o f Costa Rica c o n s i s t s o f basalt, minor bedded chert, p l u t o n i c rocks.

(2) deep

and mafic

They suggest t h a t t h e r h y t h m i c a l l y bedded r a d i o l a r i a n c h e r t

accumulated i n an abyssal environment o f considerable r e l i e f i n t h e Mesozoic eastern P a c i f i c . Clear deposition studies.

evidence of

related

bedded

to

chert

the

depositional

sequences

has

not

settings been

Analyses o f the chemical coriiposition o f

and mechanism of

forthcoming

in

most

bedded c h e r t sequences,

4

however, are becoming very e f f e c t i v e f o r understandiny these basic sediilientary aspects o f c h e r t s as i s demonstrated i n papers o f Chapters 10, 11, and 12. Hein and co-workers suggest t h a t c h e r t s from western Costa Rica,

includiny the

Nicoya Complex, were deposited as t u r b i d i t e s o f mostly s i l i c e o u s d e b r i s i n deep water,

b u t near a c o n t i n e n t a l margin.

The d i s t i n c t coiliposition o f t h e Nicoya

Complex c h e r t s r e l a t i v e t o t h e open-ocean analyses o f bedded c h e r t s i n Japan, f o u r groups of elements: K,

Na, Mg,

Fe,

Cr,

c h e r t s from DSDP holes

Matsumoto and I i j i m a d i s c r i m i n a t e amony

SiO2 represents mostly biogenic s i l i c a ;

Rb occur i n d e t r i t a l components; Mn, Fe,

occur rnostly i n a u t h i g e n i c o r hydroyenous a d d i t i o n s ; carbonates.

By

using

t h e Mn/Al

sedimentation decreases,

i s well

Si0~-Al~0~-(Fe~0~+MnO)xlO. From cheiliical

i l l u s t r a t e d on a t e r n a r y p l o t of

ratio

that

Si, Al,

Ti,

V,

Zn,

Cu,

Ni,

and Ca and S r occur i n

increases

as

the

rate

of

they show t h a t r a d i o l a r i a n c h e r t beds i n a back-arc

marginal sea o f t h e Permian and T r i a s s i c Chichibu Terrane were deposited s l o w l y whereas

alternating

shale

layers

were

deposited

rapidly.

In

contrast,

radiolarian-diatomaceous bedded c h e r t s o f t h e T e r t i a r y Setogawa Terrane were deposited

i n an offshore,

arc-trench-gap

r a p i d l y than t h e Chichibu cherts. froin many p a r t s o f t h e world, mechanism o f

but

accumulated much more

Steinberg and co-workers

shou t h a t no s i n g l e

d e p o s i t i o n can describe a l l bedded c h e r t sequences,

siliceous turbidites, Al-Fe-Ti

basin

Based on the chemical composition o f c h e r t s

p e l a g i c deposition,

and t h a t

and diagenesis a l l p l a y a part.

Si-

and REE f l u c t u a t i o n s i n p e l a y i c r a d i o l a r i t e sequences correspond t o

changes i n paleogeography. Chapters 13 through 17 concern various aspects o f diayenesis: do s i l i c e o u s sediments l i t h i f y i n t o c h e r t s ? experinients

that

magnesium

hydroxide

t r a n s f o r m a t i o n o f opal-A t o opal-CT. of

early

diagenesis.

Dissolved

How and when

Kastner and Gieskes c o n f i r m from

compounds

foriii

as

nuclei

the

Nucleation i s slow under t h e c o n d i t i o n s silica

values

from

the

r a d i o l a r i a n s vary depending on temperature and a l k a l i n i t y .

dissolution

150°C t h e s o l u b i l i t y exceeds t h a t o f opal-A

of

Up t o 100°C t h e

s o l u b i 1it y o f t h e r a d i o l a r i ans approaches the s o l u b i 1it y o f opal -C, consumed.

for

whereas a t

a f t e r t h e a l k a l i n i t y has been

Based on p e t r o l o g i c a l study o f the Neogene s i l i c e o u s deposits o f

n o r t h e r n Japan, Tada and I i j i m a s h w t h a t various 4 A o p a l i n e phases form from different

materials.

Opal-CT

forms

from b i o g e n i c

opal;

o r i g i n a t e s from t h e a l t e r a t i o n o f s i l i c i c volcanic glass;

low c r i s t o b a l i t e

and t r i d y m i t e forms

by d i r e c t p r e c i p i t a t i o n as a l a t e stage weathering product.

They c o n f i r m t h e

i d e n t i f i c a t i o n o f mixtures o f t h e o p a l i n e phases by means o f X - r a y diffraction.

Garrison,

powder

Isaacs, and P i s c i o t t o describe t h e l i t h o f a c i e s o f t h e

Monterey Formation o f C a l i f o r n i a which i n c l u d e a lower calcareous-phosphatic f a c i e s and an upper s i l i c e o u s facies.

They show t h a t t h e s i l i c a diagenesis i s

c o n t r o l l e d by temperature and sediment composition such as t h e c l a y mineral

5

content.

Transformation o f

opal-A

and opal-CT

occurred by

rapid solution-

p r e c i p i t a t i o n accompanied by s i y n i f i c a n t compaction and by l i t t l e irioveirient o f s i l i c a between beds.

M i z u t a n i and Shibata note t h a t t h e Rb-Sr and K - A r whole

rock age o f s i l i c e o u s shales from t h e Mino D i s t r i c t , c e n t r a l Japan are about 18 my. less than t h e Middle Jurassic aye determined from r a d i o l a r i a n asseniblages, suygestiny t h a t 18 m.y.

were r e q u i r e d f o r diagenesis t o c l o s e t h e chemical

system w i t h respect t o t h e elements analyzed. chert

sections

cornpositions

i n Greece and I t a l y ,

that

the

temperatures

With samples from Cretaceous

Baltuck of

deduces from oxygen

diayenesis

were

greater

isotopic

for

cherts

associated w i t h inudstone than f o r those associated w i t h carbonate. Diatomaceous sediments are w i d e l y d i s t r i b u t e d both on t h e sea f l o o r i n h i g h l a t i t u d e areas and i n n o r t h e r n Japan and C a l i f o r n i a as discussed i n Chapters 19,

18,

and 20.

content

from

sediments.

B r e u s t e r proposes a method t o determine t h e biogenic opal the

bulk

chemical

composition

of

Antarctic

o f d e t r i t a l components from t h e t o t a l s i 1i c a content. that

diatoms

froiii B e r i n g Sea surface

stream,

productivity paleoclimatic assernblayes. activity,

sea-ice

conditions,

dichrotherrnal

water.

environments

of

deposits

Sancetta demonstrates

record the

hydrography and

D i f f e r e n t diatom assemblages d i s t i n g u i s h t h e

p r o d u c t i v i t y o f o v e r l y i n g waters. Alaskan

diatomaceous

The b i o y e n i c opal content can be obtained by s u b t r a c t i n g t h e s i l i c a

low-salinity Koizunii

shelf

discusses

Neoyene sections

as

water,

the

and

high-

sedimentary

determined frorii

and

diatom

Increased diatom p r o d u c t i o n d i d not always correspond t o v o l c a n i c

but t o c l i m a t i c c o o l i n g and t e c t o n i c d i f f e r e n t i a t i o n o f d e p o s i t i o n a l

basins which caused upwelling. Widespread Mesozoic and Late Paleozoic bedded c h e r t s o f southwest Japan are described and discussed r a d i o l a r i a n assemblages

i n Chapters 21 through 25. identified

Yao reviews

sixteen

from Mesozoic mudstone and chert.

New

assemblages d e f i n i n g p a r t s o f t h e T r i a s s i c and J u r a s s i c are described. describes t h e sedimentary s t r u c t u r e s i n Permian-Triassic District,

Imoto

c h e r t s o f t h e Tarnba

s t r u c t u r e s t h a t i n d i c a t e d e p o s i t i o n o f s i l i c e o u s d e b r i s by t u r b i d i t y

c u r r e n t s and/or bottom currents.

Nakazawa and co-workers describe bedded c h e r t

o f Cretaceous aye from the Shimanto B e l t , K i i Peninsula,

and suggest t h a t t h e

c h e r t formed i n a r e g i o n o f o f f - r i d g e volcanisin where inuch t e r r i g e n o u s d e b r i s accuniulated.

Ogawa.

Nakashirria,

and Sunouchi

propose t h a t many interbedded

sandstone-chert sections i n southwest Japan i n c l u d i n g t h e Shiilianto B e l t r e s u l t from t e c t o n i c i n t e r l a y e r i n g o f oceanic c h e r t and i s l a n d arc sandstone d u r i n g a c c r e t i o n associated w i t h mineralogic

composition

subduction. of

associated w i t h greenstones. chlorite,

and hematite

Sano describes

rhythmically

layered

the

occurrence

chert-shale

Q u a r t z v a r i e s i n v e r s e l y w i t h plagioclase,

i n c h e r t beds and mineral

and

sequences illite,

abundances a r e arranged

syrnmetrically about t h e center o f the beds, quartz being nnst abundant a t t h e

6

center. I n the

final

laminite,

to

laminae.

chapter,

describe

Yoshida

rocks

proposes

consisting

a new l i t h o l o g i c term, cherto f a l t e r n a t i n g quartz-claystone

Rocks belonging t o t h i s group are sedimentary but i n t h e past were

mistakenly

described

argillites.

The c h e r t - l a m i n i t e occurs i n many geosynclinal basins.

as

metamorphic

phyllites,

pelitic

schists,

or