Present-Day Zeolitic Diagenesis of the Neogene Geosynclinal

27 Present-Day Zeolitic Diagenesis of the Neogene Geosynclinal Deposits in the

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Niigata O i l Field, Japan AZUMA IIJIMA Geological Institute, University of Tokyo, Hongo, Tokyo, Japan

MINORU UTADA Institute of Earth Science, University of Tokyo, Komaba, Tokyo, Japan Three deep drillings recently have penetrated through nearly horizontal strata of thick sedimentary piles beneath the Niigata Plain. Authigenic zeolites, associated with opal or quartz, were found in felsic tuffs of the drillings, and are distributed in a vertically zonal arrangement which is divided into 5 zones: from the surface, (I) fresh glass, (II) alkali clinoptilolite, (III) mordenite, (IV) analcime, and (V) albite. The zones are forming in response to temperature increases with increasing depth of burial. The clinoptilolite or mordenite-analcime and the analcime-albite transitions occur at 84°-91°C and 120°-124°C, respectively, in the presence of quartz and interstitial water. The zeolitic transitions may be a geothermometer in marine deposits which have not been subjected to local hydrothermal alteration.

T y j T o r e t h a n 8000 meters of t h e U p p e r C e n o z o i c m a r i n e deposits fill t h e U e t s u g e o s y n c l i n e a l o n g t h e coast of t h e S e a of J a p a n i n N o r t h e r n H o n s h u . T h r e e d r i l l i n g s , e a c h a b o u t 5000 meters d e e p , p r o m o t e d b y t h e Japanese P e t r o l e u m D e v e l o p m e n t C o r p . , r e c e n t l y h a v e p e n e t r a t e d t h e deposits b e n e a t h t h e N i i g a t a P l a i n , o n e of t h e i m p o r t a n t o i l a n d gas fields i n Japan.

T h e y are O b u c h i , S h i m o i g a r a s h i , a n d M a s u g a t a , w h i c h are

l o c a t e d g e o l o g i c a l l y i n a b r o a d s y n c l i n o r i u m ( F i g u r e 1 ). T h e p e n e t r a t e d 342 In Molecular Sieve Zeolites-I; Flanigen, E., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1974.


27.

IIJIMA AND UTADA

Present-Day

Figure 1.

Location

Zeolite

343

Diagenesis

and geological map

strata are h o r i z o n t a l or gently f o l d e d , a n d m a x i m u m d i p s are 10°. A l l were

deposited

i n marine

environments

since

the

middle

Miocene.

N u m e r o u s b e d s of p y r o c l a s t i c r o c k are f o u n d t h r o u g h o u t the i n t e r c a l a t e d b y n o r m a l clastic sediments.

deposits,

M o s t are t h i n a n d

m e d i u m - g r a i n e d v i t r i c tuffs of r h y o l i t e a n d dacite.

fine-

to

T h e tuffs alter, to

v a r y i n g degrees, to a n aggregate of a u t h i g e n i c m i n e r a l s . A u t h i g e n i c m i n e r a l s i n 224 samples w e r e i d e n t i f i e d b y x - r a y p o w d e r diffraction a n d microscope.

T h e y are as f o l l o w s :

zeolites: c l i n o p t i l o l i t e , m o r d e n i t e , a n a l c i m e , l a u m o n t i t e . c l a y m i n e r a l s : m o n t m o r i l l o n i t e , corrensite, c h l o r i t e , c e l a d o n i t e , i l l i t e . silica minerals: opal, quartz. alkali feldspars: albite, monoclinic K-feldspar. carbonate: These

calcite.

m i n e r a l s , especially zeolites, are d i s t r i b u t e d i n v e r t i c a l l y z o n a l

arrangement, w h i c h w e d i v i d e i n t o 5 zones—i.e., f r o m the surface, fresh glass, ( I I )

alkali clinoptilolite, (III)

mordenite,

(IV)

(I)

analcime,

a n d ( V ) a l b i t e zones ( F i g u r e 2 ) . Z o n e I is c h a r a c t e r i z e d b y the g e n e r a l o c c u r r e n c e of fragments

of

fresh r h y o l i t e a n d d a c i t e glass w h i c h are c o a t e d w i t h m o n t m o r i l l o n i t e a n d o p a l . Z o n e I I is c h a r a c t e r i z e d b y a l k a l i c l i n o p t i l o l i t e t h a t is stable to h e a t i n g at 7 5 0 ° C for 12 hours a n d t r e a t i n g w i t h h o t 6N

hydrochloric

a c i d for 1 h o u r . T h e m i n u t e crystals of a l k a l i c l i n o p t i l o l i t e fill the v o i d s r e s u l t i n g f r o m d i s s o l v e d glass shards, a n d are associated w i t h o p a l , m o n t m o r i l l o n i t e , a n d sometimes celadonite.

T h e m o d e of o c c u r r e n c e s t r o n g l y

suggests that it w a s f o r m e d b y r e a c t i o n of felsic glass w i t h i n t e r s t i t i a l

In Molecular Sieve Zeolites-I; Flanigen, E., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1974.

344

MOLECULAR SIEVE ZEOLITES 1


I

II

III

IV

V

FELSIC GLASS ALKALI-CLINOPTILOLITE MORDENITE Ca-CLINOPTILOLITE ANALCIME LAUMONTITE ALBITE Albitized PLAGIOCLASE K-FELDSPAR OPAL QUARTZ MONTMORILLONITE CORRENSITE CHLORITE CELADONITE ILLITE Figure 2. sediments.

Diagenetic zones of authigenic minerals in tuffs and tuffaceous The length of the zone is roughly proportional to the depth range.

w a t e r — o r i g i n a l l y sea w a t e r . P r i m a r y fragments of q u a r t z , feldspars, a n d b i o t i t e are u n a l t e r e d . F r a g m e n t s o f r e l i c glass are n o t u n c o m m o n . Z o n e I I I is c h a r a c t e r i z e d b y m o r d e n i t e , t h o u g h its o c c u r r e n c e i s rather s p o r a d i c .

I n tuffs of t h e M a s u g a t a d r i l l i n g , C a - c l i n o p t i l o l i t e is

c o m m o n , w h i c h is stable to h e a t i n g u p t o 750 ° C b u t d e s t r o y e d b y h o t h y d r o c h l o r i c a c i d . A l k a l i c l i n o p t i l o l i t e is c o m m o n i n tuffs o f t h e other 2 d r i l l i n g s . M o r d e n i t e a n d c l i n o p t i l o l i t e sometimes coexist, b u t also o c c u r separately. T h e y fill t h e v o i d s r e s u l t i n g f r o m d i s s o l v e d glass shards a n d c e m e n t t h e i n t e r s t i t i a l pores o f tuffs w h e r e t h e y a r e associated w i t h o p a l o r c h a l c e d o n i c q u a r t z , m o n t m o r i l l o n i t e , a n d sometimes c e l a d o n i t e . denite a n d alkali clinoptilolite were probably formed

Mor-

b y r e a c t i o n of

felsic glass w i t h i n t e r s t i t i a l solutions, whereas C a - c l i n o p t i l o l i t e m a y b e p r o d u c e d b y t h e c a t i o n exchange r e a c t i o n of a l k a l i c l i n o p t i l o l i t e . T h e p r i m a r y m i n e r a l s of t h e tuffs a r e u n a l t e r e d , a n d t h e o r i g i n a l v i t r o c l a s t i c texture is w e l l p r e s e r v e d . N o fresh glass shards r e m a i n i n this zone. A n a l c i m e is specific i n Z o n e I V . U n d e r t h e m i c r o s c o p e , i t occurs c o m m o n l y as t h e p s e u d o m o r p h s

of chnoptilolite a n d mordenite w h i c h

r e p l a c e d glass shards o r c e m e n t e d t h e i n t e r s t i t i a l pores o f tuffs.

Mor-

d e n i t e a n d C a - c l i n o p t i l o l i t e f r e q u e n t l y coexist w i t h a n a l c i m e , h o w e v e r . A u t h i g e n i c q u a r t z appears as m i c r o c r y s t a l l i n e aggregates i n t h e cement a n d is associated w i t h m o n t m o r i l l o n i t e , corrensite, o r c h l o r i t e .


Mont-

27.

IIJIMA AND UTADA

Present-Day

Zeolite

345

Diagenesis

m o r i l l o n i t e g r a d u a l l y changes to c h l o r i t e t h r o u g h corrensite o r s w e l l i n g c h l o r i t e i n t h e l o w e r p a r t of this zone.

P r i m a r y crystals of q u a r t z a r e

almost u n a l t e r e d except w h e r e r e p l a c e d b y calcite. P l a g i o c l a s e is s l i g h t l y a l b i t i z e d i n t h e l o w e r p a r t of t h e zone.

T h e o r i g i n a l v i t r o c l a s t i c texture

is r e c o g n i z e d easily. Tuffs i n this z o n e r e t a i n 15 t o 2 0 % p o r o s i t y (8, 9 ) . Z o n e V is c h a r a c t e r i z e d b y t h e coexistence of a u t h i g e n i c a l b i t e w i t h analcime.

T h e a l b i t e is f o r m e d b y r e a c t i o n of a n a l c i m e w i t h q u a r t z i n

the presence (oligoclase

of i n t e r s t i t i a l w a t e r .

to andesine)

texture b e c o m e s v a g u e

occurs

A l b i t i z a t i o n of p r i m a r y p l a g i o c l a s e

extensively.

T h e original vitroclastic

t h r o u g h c r y s t a l l i z a t i o n of q u a r t z a n d a l b i t e .


L a u m o n t i t e p r e c i p i t a t e s i n cavities, l i n e d w i t h q u a r t z , of augite d a c i t e l a v a a n d v o l c a n i c b r e c c i a of t h e M a s u g a t a d r i l l i n g a n d d o l e r i t e sheet of the O b u c h i d r i l l i n g . T h e s t u d y area has b e e n t h e site of d e p o s i t i o n since t h e m i d d l e M i o c e n e , a n d t h e deposits h a v e b e e n little, i f a n y , d i s t u r b e d b y tectonic

MASUGATA

SHIMOI GARASHI

OBUCHI

5 - "

Figure 3. Relation of zeolitic zonation to stratigraphie subdivision. U: Uonuma group, W: Wanazu fm., H: Haizume fm., Ni: Nishiyama fm., S: Shiiya fm., Na: Nanatani fm. Solid lines show the boundaries of the zeolitic zonation and dotted lines represent the stratigraphie subdivision.


346

MOLECULAR SIEVE ZEOLITES


Table I.

Ranges of Temperature, Depth, and T o t a l Pressure of the Upper Limit of Each Diagenetic Zone

Zone

Temperature Range of the Upper Limit, °C

Depth Range, Meters

II. Clinoptilolite III. Mordenite I V . Analcime V. Albite

41-49 55-59 84-91 120-124

800-1900 1450-2400 2900-3500 4150-4500

Total Pressure Range, Kb 0.4-0.7 0.9-1.1

1.3-1.4

TEMPERATURE ( °C) 100 50

0

150

E2

0_ UJ . Q

Present-Day Zeolitic Diagenesis of the Neogene Geosynclinal

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